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Rev 130 Rev 156
Project History
Project History
---------------
---------------
14-Nov-2002
14-Nov-2002
Project launched.
Project launched.
Main makefile written.
Main makefile written.
Directory structure created.
Directory structure created.
15-Nov-2002
15-Nov-2002
Kernel of UNIX 7th Edition copied.
Kernel of UNIX 7th Edition copied.
Download and installation of lcc.
Download and installation of lcc.
This included the following steps:
This included the following steps:
1) In 'src', copy 'mips.md' to 'eco32.md' without changes,
1) In 'src', copy 'mips.md' to 'eco32.md' without changes,
   except that the interface record is named 'eco32IR'.
   except that the interface record is named 'eco32IR'.
   The code output remains for now as it is in 'mips.md'.
   The code output remains for now as it is in 'mips.md'.
2) Add instructions to makefile for compiling 'eco32.md'.
2) Add instructions to makefile for compiling 'eco32.md'.
3) In 'src', add the interface record definition 'eco32IR'
3) In 'src', add the interface record definition 'eco32IR'
   to the file 'bind.c'.
   to the file 'bind.c'.
4) Add a directory 'include/eco32/linux' and copy all header
4) Add a directory 'include/eco32/linux' and copy all header
   files from the corresponding directory for the mips processor.
   files from the corresponding directory for the mips processor.
5) In 'etc', copy 'irix.c' to 'eco32-linux.c' and change the
5) In 'etc', copy 'irix.c' to 'eco32-linux.c' and change the
   contents of this file to properly call the preprocessor,
   contents of this file to properly call the preprocessor,
   the compiler, etc.
   the compiler, etc.
6) Add the option -DLCCDIR=\"$(BUILDDIR)/\" to the instruction
6) Add the option -DLCCDIR=\"$(BUILDDIR)/\" to the instruction
   in the makefile which compiles $(HOSTFILE).
   in the makefile which compiles $(HOSTFILE).
7) In 'src', substitute 'lex.c' with a newer version, which
7) In 'src', substitute 'lex.c' with a newer version, which
   computes the types of hexadecimal constants correctly.
   computes the types of hexadecimal constants correctly.
Disk creator done.
Disk creator done.
Program to write the bootstrap sector done.
Program to write the bootstrap sector done.
16-Nov-2002
16-Nov-2002
Preliminary instruction formats defined.
Preliminary instruction formats defined.
Preliminary instruction set constructed.
Preliminary instruction set constructed.
Some ideas for an address translation unit noted.
Some ideas for an address translation unit noted.
17-Nov-2002
17-Nov-2002
Final instruction formats defined.
Final instruction formats defined.
Preliminary version of simulator finished.
Preliminary version of simulator finished.
19-Nov-2002
19-Nov-2002
Instruction set cleanup done.
Instruction set cleanup done.
Work on assembler started.
Work on assembler started.
23-Nov-2002
23-Nov-2002
Four of the five ROMs translated to ECO32.
Four of the five ROMs translated to ECO32.
24-Nov-2002
24-Nov-2002
Preliminary version of assembler/linker/loader finished.
Preliminary version of assembler/linker/loader finished.
25-Nov-2002
25-Nov-2002
Bootstrap monitor ROM translated to ECO32.
Bootstrap monitor ROM translated to ECO32.
Simulator is running.
Simulator is running.
Bootstrap sector on disk created.
Bootstrap sector on disk created.
Now it is possible to boot from the disk.
Now it is possible to boot from the disk.
26-Nov-2002
26-Nov-2002
Work on an ECO32 back-end for the C compiler started.
Work on an ECO32 back-end for the C compiler started.
27-Nov-2002
27-Nov-2002
Preliminary version of back-end done.
Preliminary version of back-end done.
28-Nov-2002
28-Nov-2002
'Load address' instruction invented as macro for a set
'Load address' instruction invented as macro for a set
of short sequences of instructions which are difficult
of short sequences of instructions which are difficult
to generate by the back-end.
to generate by the back-end.
29-Nov-2002
29-Nov-2002
Startup code (c0.s, c1.s) revised.
Startup code (c0.s, c1.s) revised.
Writing the bootstrap sector revised.
Writing the bootstrap sector revised.
System ROMs revised.
System ROMs revised.
Tests revised.
Tests revised.
30-Nov-2002
30-Nov-2002
Started to program the MMU.
Started to program the MMU.
Surprise: we don't need an MMU enable bit! The unit can be
Surprise: we don't need an MMU enable bit! The unit can be
switched on all the time, but we have to be careful not to
switched on all the time, but we have to be careful not to
use the TLB before it is properly initialized.
use the TLB before it is properly initialized.
01-Dec-2002
01-Dec-2002
Interrupt system re-designed.
Interrupt system re-designed.
Added the last missing case in the 'lda' implementation.
Added the last missing case in the 'lda' implementation.
Timer interrupt is working properly.
Timer interrupt is working properly.
We now have a new instruction: 'nor'. With this it is easy
We now have a new instruction: 'nor'. With this it is easy
to implement the bitwise complement of an integer. Done.
to implement the bitwise complement of an integer. Done.
The compiler option -Wo-kernel compiles a program so that
The compiler option -Wo-kernel compiles a program so that
it can be run in kernel mode.
it can be run in kernel mode.
This is a big step forward: hello.c is running (in kernel
This is a big step forward: hello.c is running (in kernel
mode of course).
mode of course).
02-Dec-2002
02-Dec-2002
The characteristic feature of kernel mode programs as well as
The characteristic feature of kernel mode programs as well as
of the kernel itself is that they want to handle all sorts of
of the kernel itself is that they want to handle all sorts of
special conditions for themselves (e.g., interrupts, exceptions,
special conditions for themselves (e.g., interrupts, exceptions,
startup code). So if the flag -Wo-kernel is given, the startup
startup code). So if the flag -Wo-kernel is given, the startup
library code (c0.s and c1.s) is no longer linked in automatically.
library code (c0.s and c1.s) is no longer linked in automatically.
03-Dec-2002
03-Dec-2002
The assembler now contains a complete expression parser which can
The assembler now contains a complete expression parser which can
handle additive, multiplicative and shift expressions as well as
handle additive, multiplicative and shift expressions as well as
unary and parenthesized expressions.
unary and parenthesized expressions.
Error in back-end corrected: mul & div instructions did not
Error in back-end corrected: mul & div instructions did not
correctly specify the second source register.
correctly specify the second source register.
04-Dec-2002
04-Dec-2002
The low-level code generators in the assembler had completely to
The low-level code generators in the assembler had completely to
be redone: they could not handle big constants (immediate values
be redone: they could not handle big constants (immediate values
and addresses) in instructions that allow only 16 bit constants.
and addresses) in instructions that allow only 16 bit constants.
05-Dec-2002
05-Dec-2002
I now have a pair of functions which allow to get/set an
I now have a pair of functions which allow to get/set an
interrupt service routine in the interrupt service routine
interrupt service routine in the interrupt service routine
table. The low-level register save/restore is handled in
table. The low-level register save/restore is handled in
assembler, but the interrupt service routine itself can be
assembler, but the interrupt service routine itself can be
written in C. An application of this principle shows how to
written in C. An application of this principle shows how to
determine the total amount of physical memory by probing
determine the total amount of physical memory by probing
the memory until a bus timeout exception occurs. This can
the memory until a bus timeout exception occurs. This can
fully be formulated in C.
fully be formulated in C.
The back-end generates a 'jal' instruction even when the
The back-end generates a 'jal' instruction even when the
argument is a register. Although it would perhaps be more
argument is a register. Although it would perhaps be more
appropriate to generate a 'jalr' instruction, I changed the
appropriate to generate a 'jalr' instruction, I changed the
assembler to accept an address as well as a register with
assembler to accept an address as well as a register with
this instruction.
this instruction.
06-Dec-2002
06-Dec-2002
TLB flush is the first instruction dealing with the TLB.
TLB flush is the first instruction dealing with the TLB.
Implemented.
Implemented.
07-Dec-2002
07-Dec-2002
Until now we only had one special processor register, the
Until now we only had one special processor register, the
processor status word. With the MMU present, this will change.
processor status word. With the MMU present, this will change.
Renamed 'gpsw' (get processor status word) to 'mvfs' (move
Renamed 'gpsw' (get processor status word) to 'mvfs' (move
from special register). Renamed 'ppsw' (put processor status
from special register). Renamed 'ppsw' (put processor status
word) to 'mvts' (move to special register). These instructions
word) to 'mvts' (move to special register). These instructions
have two arguments: a single register and a number specifying
have two arguments: a single register and a number specifying
the special register.
the special register.
It is perhaps better to use an established set of instructions
It is perhaps better to use an established set of instructions
dealing with the TLB (i.e., the way MIPS is doing this) instead
dealing with the TLB (i.e., the way MIPS is doing this) instead
of an even more minimalistic one, which is not guaranteed to
of an even more minimalistic one, which is not guaranteed to
cover all cases. So I will abandon 'TLB flush' in favor of the
cover all cases. So I will abandon 'TLB flush' in favor of the
four instructions found in the MIPS instruction set ('tbs',
four instructions found in the MIPS instruction set ('tbs',
'tbwr', 'tbri', and 'tbwi').
'tbwr', 'tbri', and 'tbwi').
As is documented in the MIPS reference book, the valid bit V is
As is documented in the MIPS reference book, the valid bit V is
not involved in the TLB matching process. Implementation changed.
not involved in the TLB matching process. Implementation changed.
Perhaps we don't need the V bit at all? I'll leave it out for now.
Perhaps we don't need the V bit at all? I'll leave it out for now.
08-Dec-2002
08-Dec-2002
Today I came up with the idea to test the MMU implementation by
Today I came up with the idea to test the MMU implementation by
running a somewhat more realistic test: a task which is compiled
running a somewhat more realistic test: a task which is compiled
for virtual address 0 and has a minimal I/O library which traps
for virtual address 0 and has a minimal I/O library which traps
to the kernel to output a character.
to the kernel to output a character.
09-Dec-2002
09-Dec-2002
It is not necessary to prepare real page tables for the task, as I
It is not necessary to prepare real page tables for the task, as I
thought initially. Since we have only one task which uses exactly
thought initially. Since we have only one task which uses exactly
two pages (code and stack), it is possible to preset the TLB with
two pages (code and stack), it is possible to preset the TLB with
two entries for the pages and then leave it alone.
two entries for the pages and then leave it alone.
The test is running.
The test is running.
10-Dec-2002
10-Dec-2002
Now for the next step: two tasks running concurrently, preempted
Now for the next step: two tasks running concurrently, preempted
by a timer interrupt. This is really a lot more complicated than
by a timer interrupt. This is really a lot more complicated than
a single task because now the entries in the TLB must be flushed
a single task because now the entries in the TLB must be flushed
and re-programmed when a task switch occurs.
and re-programmed when a task switch occurs.
Another complication is the need for two kernel-mode stacks, one
Another complication is the need for two kernel-mode stacks, one
for each task, in addition to the task-specific user-mode stacks.
for each task, in addition to the task-specific user-mode stacks.
This is necessary because of two facts:
This is necessary because of two facts:
  - the kernel cannot rely on the integrity of the user-mode stacks
  - the kernel cannot rely on the integrity of the user-mode stacks
  - the state of the suspended task must be preserved somewhere,
  - the state of the suspended task must be preserved somewhere,
    even if the other task is running and trapping to the kernel
    even if the other task is running and trapping to the kernel
    for a system call.
    for a system call.
11-Dec-2002
11-Dec-2002
This was indeed much harder than expected, but now it works.
This was indeed much harder than expected, but now it works.
12-Dec-2002
12-Dec-2002
It is evident that only a very short sequence of instructions is
It is evident that only a very short sequence of instructions is
able to handle a TLB miss exception efficiently. MIPS is doing
able to handle a TLB miss exception efficiently. MIPS is doing
this by giving the TLB miss exception a separate interrupt vector.
this by giving the TLB miss exception a separate interrupt vector.
We don't want to go so far, but of course we cannot tolerate to
We don't want to go so far, but of course we cannot tolerate to
execute all the lengthy actions at the beginning of the standard
execute all the lengthy actions at the beginning of the standard
trap handler. So we will sort out the TLB miss exception at the
trap handler. So we will sort out the TLB miss exception at the
very beginning of the standard exception handling.
very beginning of the standard exception handling.
13-Dec-2002
13-Dec-2002
It is easy to catch the TLB miss - but how should it be handled?
It is easy to catch the TLB miss - but how should it be handled?
Some sort of page table has to supply the necessary information
Some sort of page table has to supply the necessary information
so that a new entry can be filled into the TLB. How should the
so that a new entry can be filled into the TLB. How should the
page tables be organized? In the past I saw cascaded page tables
page tables be organized? In the past I saw cascaded page tables
as the only solution. But it might be better to have a single
as the only solution. But it might be better to have a single
page table which itself is paged and lies in virtual memory.
page table which itself is paged and lies in virtual memory.
The big advantages of this scheme are fast access (no pointers
The big advantages of this scheme are fast access (no pointers
to chase) and (almost) no waste of memory because gaps in the
to chase) and (almost) no waste of memory because gaps in the
table do not need any real memory. But then of course we have
table do not need any real memory. But then of course we have
to handle TLB misses while accessing the page table...
to handle TLB misses while accessing the page table...
Very confusing!
Very confusing!
14-Dec-2002
14-Dec-2002
What information is needed in which format if a TLB miss (or any
What information is needed in which format if a TLB miss (or any
other TLB exception) occurs? I really have no stringent answer to
other TLB exception) occurs? I really have no stringent answer to
this question, so I will follow again a minimalistic design path:
this question, so I will follow again a minimalistic design path:
Implement a register in the MMU which is set to the offending
Implement a register in the MMU which is set to the offending
virtual address in case the translation didn't work. Done.
virtual address in case the translation didn't work. Done.
As I realize now, this hardware equipment can support a variety of
As I realize now, this hardware equipment can support a variety of
different organizations of the page tables handled by software.
different organizations of the page tables handled by software.
Even inverted page tables seem feasible!
Even inverted page tables seem feasible!
It would be very convenient if the kernel could use another
It would be very convenient if the kernel could use another
register without having to save its contents first. I think
register without having to save its contents first. I think
we could let the kernel have also register 28 at its disposal.
we could let the kernel have also register 28 at its disposal.
17-Dec-2002
17-Dec-2002
Yesterday I realized that the 'lda' macro instruction is no longer
Yesterday I realized that the 'lda' macro instruction is no longer
needed because 'add' does the very same job. Deleted.
needed because 'add' does the very same job. Deleted.
18-Dec-2002
18-Dec-2002
It is very desirable to have an interrupt mask in the PSW.
It is very desirable to have an interrupt mask in the PSW.
If, e.g., the timer interrupts and the timer ISR decides to
If, e.g., the timer interrupts and the timer ISR decides to
disable interrupts from all devices but the timer itself,
disable interrupts from all devices but the timer itself,
then this is not easily achievable without a central mask.
then this is not easily achievable without a central mask.
19-Dec-2002
19-Dec-2002
One's complement, represented by '~', is another operator
One's complement, represented by '~', is another operator
implemented in the assembler.
implemented in the assembler.
20-Dec-2002
20-Dec-2002
As well as bitwise and, bitwise xor, and bitwise or,
As well as bitwise and, bitwise xor, and bitwise or,
represented by '&', '^', and '|', respectively. These
represented by '&', '^', and '|', respectively. These
operators are left associative and have the same priority
operators are left associative and have the same priority
as they have in C, i.e., & > ^ > |, in order of decreasing
as they have in C, i.e., & > ^ > |, in order of decreasing
priority.
priority.
21-Dec-2002
21-Dec-2002
Because of the new structure of the PSW all tests must be
Because of the new structure of the PSW all tests must be
updated and carried out once more. A lot of work...
updated and carried out once more. A lot of work...
22-Dec-2002
22-Dec-2002
I spotted a minor bug in the simulator: a breakpoint which
I spotted a minor bug in the simulator: a breakpoint which
was set to address C0000004 in order to catch any interrupt
was set to address C0000004 in order to catch any interrupt
or exception will not work for exceptions. This is due to
or exception will not work for exceptions. This is due to
the handling of exceptions by setjmp/longjmp. Corrected.
the handling of exceptions by setjmp/longjmp. Corrected.
23-Dec-2002
23-Dec-2002
ECO32 Version 0.0 released.
ECO32 Version 0.0 released.
26-Dec-2002
26-Dec-2002
Today I started to convert the original sources of
Today I started to convert the original sources of
UNIX 7th Edition to ANSI C.
UNIX 7th Edition to ANSI C.
29-Dec-2002
29-Dec-2002
I found a real programming error in the text.c module:
I found a real programming error in the text.c module:
  if (ip->i_flag&ITEXT==0) return;
  if (ip->i_flag&ITEXT==0) return;
My compiler warned: 'expression with no effect elided'.
My compiler warned: 'expression with no effect elided'.
'==' has higher precedence than '&', but ITEXT does not
'==' has higher precedence than '&', but ITEXT does not
equal zero, so the whole test expression becomes zero
equal zero, so the whole test expression becomes zero
and the return is never executed. The line should read:
and the return is never executed. The line should read:
  if ((ip->i_flag&ITEXT)==0) return;
  if ((ip->i_flag&ITEXT)==0) return;
31-Dec-2002
31-Dec-2002
The masters made a typoe: in the file kl.c, the function
The masters made a typoe: in the file kl.c, the function
named 'ttioccomm' is spelled 'ttioccom'. I think this
named 'ttioccomm' is spelled 'ttioccom'. I think this
did go undetected because of the very restricted length
did go undetected because of the very restricted length
of symbols with external linkage.
of symbols with external linkage.
01-Jan-2003
01-Jan-2003
Today I began investigating the startup procedure. I will
Today I began investigating the startup procedure. I will
place the per-process kernel stack in the top half of the
place the per-process kernel stack in the top half of the
u area, which itself is one page in size and is located
u area, which itself is one page in size and is located
directly underneath the kernel at 0xC0000000 - 0x1000.
directly underneath the kernel at 0xC0000000 - 0x1000.
This part of the virtual address space is mapped and so
This part of the virtual address space is mapped and so
the u area of the running process is always accessible.
the u area of the running process is always accessible.
02-Jan-2003
02-Jan-2003
How do we do the memory management? This is THE central
How do we do the memory management? This is THE central
question of our porting effort. One possibility which
question of our porting effort. One possibility which
offers the chance of only minor changes to the existing
offers the chance of only minor changes to the existing
sources would be to keep the management by the coremap
sources would be to keep the management by the coremap
array, but with the granularity changed to 4 k, the page
array, but with the granularity changed to 4 k, the page
size. This route of course would not barely touch the
size. This route of course would not barely touch the
power of demand paging, which is possible by our hardware.
power of demand paging, which is possible by our hardware.
Nevertheless, I will follow this path for the time being.
Nevertheless, I will follow this path for the time being.
I changed the coremap/swapmap entries into structs of two
I changed the coremap/swapmap entries into structs of two
integers instead of two shorts. Otherwise the range of
integers instead of two shorts. Otherwise the range of
addresses might get too small (although this is unlikely:
addresses might get too small (although this is unlikely:
64 k pages of 4 k bytes each equals 256 M bytes - quite a
64 k pages of 4 k bytes each equals 256 M bytes - quite a
lot of memory).
lot of memory).
04-Jan-2003
04-Jan-2003
This last change is nonsense - much of the other stored
This last change is nonsense - much of the other stored
information about processes would have to be changed also.
information about processes would have to be changed also.
Reverted.
Reverted.
Because ECO32 does not have two different stack pointers
Because ECO32 does not have two different stack pointers
(as the PDP-11 has) we must switch to the kernel stack
(as the PDP-11 has) we must switch to the kernel stack
explicitly. But we must not do the switch if the interrupt
explicitly. But we must not do the switch if the interrupt
hit while the machine was running in kernel mode already -
hit while the machine was running in kernel mode already -
then the sp points deep into a properly setup kernel stack.
then the sp points deep into a properly setup kernel stack.
Switching stacks would then destroy the stack completely.
Switching stacks would then destroy the stack completely.
11-Jan-2003
11-Jan-2003
I discovered a mysterious overwriting of some bytes of
I discovered a mysterious overwriting of some bytes of
the loaded UNIX kernel. This took place even before any
the loaded UNIX kernel. This took place even before any
of its code was executed! A little bit of searching, and
of its code was executed! A little bit of searching, and
the guilty one was found: the bootmon ROM code and its
the guilty one was found: the bootmon ROM code and its
stack. Now there is a problem: where should we put the
stack. Now there is a problem: where should we put the
stack of the bootmon ROM?
stack of the bootmon ROM?
We have two ways to get some program into the bare machine:
We have two ways to get some program into the bare machine:
a) The 'realistic hardware' scenario: a ROM holds an initial
a) The 'realistic hardware' scenario: a ROM holds an initial
program which e.g. may boot the operating system from disk.
program which e.g. may boot the operating system from disk.
b) The 'convenient debugging scenario': the program, e.g. the
b) The 'convenient debugging scenario': the program, e.g. the
operating system, is somewhat magically loaded into RAM.
operating system, is somewhat magically loaded into RAM.
The error described above is caused by the unwanted interaction
The error described above is caused by the unwanted interaction
of a) and b) when used together. So I think that the correct
of a) and b) when used together. So I think that the correct
solution of the problem is to forbid the specification of both
solution of the problem is to forbid the specification of both
simulator options -r and -l at the same time.
simulator options -r and -l at the same time.
13-Jan-2003
13-Jan-2003
The simulator uses all CPU power which is available, even
The simulator uses all CPU power which is available, even
when only waiting for a command line. This can easily be
when only waiting for a command line. This can easily be
changed by inserting a usleep(100) call into the input
changed by inserting a usleep(100) call into the input
waiting loop of the curses interface. Done.
waiting loop of the curses interface. Done.
Two new pseudo-ops (.syn and .nosyn) added to the assembler.
Two new pseudo-ops (.syn and .nosyn) added to the assembler.
They allow or disallow synthesizing instructions with 'big'
They allow or disallow synthesizing instructions with 'big'
constants, respectively. This can be used e.g. in the TLB miss
constants, respectively. This can be used e.g. in the TLB miss
handler, where much finer control over the usage of register
handler, where much finer control over the usage of register
$1 is needed.
$1 is needed.
15-Jan-2003
15-Jan-2003
The constant BSLOP in param.h must be set to 0. Otherwise there
The constant BSLOP in param.h must be set to 0. Otherwise there
would exist blocks which don't start at an address which is a
would exist blocks which don't start at an address which is a
multiple of 4. This would result in a Bus Address Error if e.g.
multiple of 4. This would result in a Bus Address Error if e.g.
an integer is fetched from the block.
an integer is fetched from the block.
16-Jan-2003
16-Jan-2003
The type mapping from C to machine types is as follows:
The type mapping from C to machine types is as follows:
         PDP-11                   ECO32
         PDP-11                   ECO32
char     byte (1 byte)            byte (1 byte)
char     byte (1 byte)            byte (1 byte)
short    word (2 bytes)           half (2 bytes)
short    word (2 bytes)           half (2 bytes)
int      word (2 bytes)           word (4 bytes)
int      word (2 bytes)           word (4 bytes)
long     double word (4 bytes)    word (4 bytes)
long     double word (4 bytes)    word (4 bytes)
T *      word (2 bytes)           word (4 bytes)
T *      word (2 bytes)           word (4 bytes)
As can be seen, only ints and pointers are differently mapped.
As can be seen, only ints and pointers are differently mapped.
This is of not much concern with in-memory data structures but
This is of not much concern with in-memory data structures but
can be desastrous with on-disk data structures (super block,
can be desastrous with on-disk data structures (super block,
inodes). Therefore we have to do the following:
inodes). Therefore we have to do the following:
a) define ino_t as unsigned short
a) define ino_t as unsigned short
b) rearrange the components in struct filsys (and in principle in
b) rearrange the components in struct filsys (and in principle in
struct dinode and struct direct too) so that no padding occurs.
struct dinode and struct direct too) so that no padding occurs.
I thought that I could simply write a disk with the PDP-11 simulator
I thought that I could simply write a disk with the PDP-11 simulator
and then use it with the ECO32 simulator; this is not possible
and then use it with the ECO32 simulator; this is not possible
due to different endianness.
due to different endianness.
17-Jan-2003
17-Jan-2003
Here are the changes I actually made:
Here are the changes I actually made:
1) in param.h:
1) in param.h:
   a) type 'ino_t' is 'unsigned short' instead of 'unsigned int'
   a) type 'ino_t' is 'unsigned short' instead of 'unsigned int'
   b) type 'dev_t' is 'short' instead of 'int'
   b) type 'dev_t' is 'short' instead of 'int'
2) in filsys.h:
2) in filsys.h:
   a) delete all components of struct filsys below the comment
   a) delete all components of struct filsys below the comment
      'remainder not maintained by this version of the system'
      'remainder not maintained by this version of the system'
   b) 's_isize' is of type 'daddr_t', not of type 'unsigned short'
   b) 's_isize' is of type 'daddr_t', not of type 'unsigned short'
   c) 's_nfree' is of type 'int', not of type 'short'
   c) 's_nfree' is of type 'int', not of type 'short'
   d) 's_ninode' is of type 'int', not of type 'short'
   d) 's_ninode' is of type 'int', not of type 'short'
   e) exchange components 's_isize' and 's_fsize'
   e) exchange components 's_isize' and 's_fsize'
3) in inode.h:
3) in inode.h:
   a) 'i_flag' is of type 'short', not of type 'char'
   a) 'i_flag' is of type 'short', not of type 'char'
   b) 'i_count' is of type 'short', not of type 'char'
   b) 'i_count' is of type 'short', not of type 'char'
The size of the superblock structure is thus increased by 6 bytes
The size of the superblock structure is thus increased by 6 bytes
to 424 bytes (well below the 512 bytes block boundary), and all
to 424 bytes (well below the 512 bytes block boundary), and all
padding or misalignment is avoided.
padding or misalignment is avoided.
18-Jan-2003
18-Jan-2003
I replaced the "Hello, world!" message in the default master boot
I replaced the "Hello, world!" message in the default master boot
record by a somewhat more appropriate message.
record by a somewhat more appropriate message.
19-Jan-2003
19-Jan-2003
In order to simplify things a bit, I removed the '-n' option from
In order to simplify things a bit, I removed the '-n' option from
the assembler. Now assembler output files always do have headers.
the assembler. Now assembler output files always do have headers.
There are of course situations in which the header must be stripped
There are of course situations in which the header must be stripped
off, e.g. with the boot record, or with the ROM in the simulator.
off, e.g. with the boot record, or with the ROM in the simulator.
We have therefore now a 'loader', a little program which converts
We have therefore now a 'loader', a little program which converts
an assembler output file into a memory image without any header.
an assembler output file into a memory image without any header.
This has the additional benefit that the simulator does no longer
This has the additional benefit that the simulator does no longer
need to know the executable format, which is especially good if we
need to know the executable format, which is especially good if we
change the format or add new formats.
change the format or add new formats.
20-Jan-2003
20-Jan-2003
Started to port the 'mkfs' utility.
Started to port the 'mkfs' utility.
21-Jan-2003
21-Jan-2003
Started to program a 'show file system' utility.
Started to program a 'show file system' utility.
22-Jan-2003
22-Jan-2003
Today I decided to spare a small number of TLB entries (4) from
Today I decided to spare a small number of TLB entries (4) from
random replacement. This helps to keep such vital information as
random replacement. This helps to keep such vital information as
the current kernel stack permanently mapped.
the current kernel stack permanently mapped.
25-Jan-2003
25-Jan-2003
I changed the disk so that it is now similar to the 'rp' device
I changed the disk so that it is now similar to the 'rp' device
in the PDP-11. This has the advantage that the usr file system
in the PDP-11. This has the advantage that the usr file system
is located on a different device (specifically: a different minor
is located on a different device (specifically: a different minor
device, i.e., a different partition) so that mounting can be tested.
device, i.e., a different partition) so that mounting can be tested.
The partitions and their intended use is as follows:
The partitions and their intended use is as follows:
   device      size in blocks     use as
   device      size in blocks     use as
  -------------------------------------------
  -------------------------------------------
    rp0           14000           whole disk
    rp0           14000           whole disk
    rp1            2000           root
    rp1            2000           root
    rp2            4000           swap
    rp2            4000           swap
    rp3            8000           usr
    rp3            8000           usr
28-Jan-2003
28-Jan-2003
This was quite a lot of work, but finally 'mkfs' is running.
This was quite a lot of work, but finally 'mkfs' is running.
The crucial tool to achieve this was 'shfs' - show file system,
The crucial tool to achieve this was 'shfs' - show file system,
which allows displaying arbitrary blocks of a disk in several
which allows displaying arbitrary blocks of a disk in several
formats (raw data, super block, inode block, directory block,
formats (raw data, super block, inode block, directory block,
free list block, or indirect block). So everything on the disk
free list block, or indirect block). So everything on the disk
can be examined in detail.
can be examined in detail.
By the way, the main hurdles to overcome had been different
By the way, the main hurdles to overcome had been different
endianness of ECO32 and x86, different padding of structures,
endianness of ECO32 and x86, different padding of structures,
and alignment restrictions with ECO32, which are not present
and alignment restrictions with ECO32, which are not present
on the x86 architecture.
on the x86 architecture.
29-Jan-2003
29-Jan-2003
Here is a short report on byte-ordering on x86, ECO32, and PDP-11.
Here is a short report on byte-ordering on x86, ECO32, and PDP-11.
The C data type 'long' is stored in 4 bytes on all thre machines,
The C data type 'long' is stored in 4 bytes on all thre machines,
as already stated above (16-Jan-2003). The order of the bytes is
as already stated above (16-Jan-2003). The order of the bytes is
different on all three machines. We number the bytes from MSB
different on all three machines. We number the bytes from MSB
(most signigicant byte) to LSB (least significant byte): then
(most signigicant byte) to LSB (least significant byte): then
the number (b1 b2 b3 b4) has the value b1*2^24+b2*2^16+b3*2^8+b4.
the number (b1 b2 b3 b4) has the value b1*2^24+b2*2^16+b3*2^8+b4.
If 'A' is the lowest (byte) address where the number is to be stored,
If 'A' is the lowest (byte) address where the number is to be stored,
then the memory layout of the three architectures look like this:
then the memory layout of the three architectures look like this:
x86       A+0:b4  A+1:b3  A+2:b2  A+3:b1    (i.e., little endian)
x86       A+0:b4  A+1:b3  A+2:b2  A+3:b1    (i.e., little endian)
ECO32     A+0:b1  A+1:b2  A+2:b3  A+3:b4    (i.e., big endian)
ECO32     A+0:b1  A+1:b2  A+2:b3  A+3:b4    (i.e., big endian)
PDP-11    A+0:b2  A+0:b1  A+0:b4  A+0:b3    (i.e., mixed)
PDP-11    A+0:b2  A+0:b1  A+0:b4  A+0:b3    (i.e., mixed)
An additional complication results from the fact that disk addresses
An additional complication results from the fact that disk addresses
in inodes on a disk are stored in a three byte format, which is
in inodes on a disk are stored in a three byte format, which is
different on ECO32 and PDP-11 (there is no such format on the x86,
different on ECO32 and PDP-11 (there is no such format on the x86,
because we don't want to run a file system on a bare PC, only within
because we don't want to run a file system on a bare PC, only within
the ECO32 simulator). In this format only the three least significant
the ECO32 simulator). In this format only the three least significant
bytes (b2 b3 b4) are stored; if b1 were non-zero an error would be
bytes (b2 b3 b4) are stored; if b1 were non-zero an error would be
triggered. So then, here are the layouts of this special format:
triggered. So then, here are the layouts of this special format:
ECO32     A+0:b2  A+1:b3  A+2:b4
ECO32     A+0:b2  A+1:b3  A+2:b4
PDP-11    A+0:b2  A+1:b4  A+2:b3
PDP-11    A+0:b2  A+1:b4  A+2:b3
As can be seen, this format is constructed on both architectures by
As can be seen, this format is constructed on both architectures by
omitting b1 (the MSB) from the four byte format.
omitting b1 (the MSB) from the four byte format.
I changed the routines that convert the three byte format from and to
I changed the routines that convert the three byte format from and to
the four byte format (iexpand() and iupdat(), both in module iget.c)
the four byte format (iexpand() and iupdat(), both in module iget.c)
in order to cope with the changed byte-ordering.
in order to cope with the changed byte-ordering.
Reduced the RAM size to 1M; this fits better to the disk swap size.
Reduced the RAM size to 1M; this fits better to the disk swap size.
Added a counter to the simulator which counts the total number of
Added a counter to the simulator which counts the total number of
instructions executed since the last reset. This helps a lot if one
instructions executed since the last reset. This helps a lot if one
wants to re-visit a specific location in the program, if a lot of
wants to re-visit a specific location in the program, if a lot of
single-stepping has been done to find the location for the first time.
single-stepping has been done to find the location for the first time.
31-Jan-2003
31-Jan-2003
There has been an inconsistency with the object file format since
There has been an inconsistency with the object file format since
its invention: the header data is stored in little endian format,
its invention: the header data is stored in little endian format,
which is convenient for the tools working in the cross development
which is convenient for the tools working in the cross development
setup. The tools running on the target architecture require the
setup. The tools running on the target architecture require the
data to be in ECO32 format of course. This is especially true for
data to be in ECO32 format of course. This is especially true for
the kernel exec file loader. Changed.
the kernel exec file loader. Changed.
03-Feb-2003
03-Feb-2003
ECO32 Version 0.1 released.
ECO32 Version 0.1 released.
04-Feb-2003
04-Feb-2003
Added to 'shfs' a command which translates an inode number into the
Added to 'shfs' a command which translates an inode number into the
block number in which this inode is located, together with an inode
block number in which this inode is located, together with an inode
number relative to that block.
number relative to that block.
The simulator's 't' command now displays also the special registers
The simulator's 't' command now displays also the special registers
of the MMU (Index, EntryHi, EntryLo, BadAddress).
of the MMU (Index, EntryHi, EntryLo, BadAddress).
Memory commands of the simulator completed.
Memory commands of the simulator completed.
05-Feb-2003
05-Feb-2003
ATTENTION: I changed the output of the disassembler to get it more
ATTENTION: I changed the output of the disassembler to get it more
consistent with the rest of the simulator, and especially with its
consistent with the rest of the simulator, and especially with its
inline assembler. There are no more '0x' prefixes in front of numbers,
inline assembler. There are no more '0x' prefixes in front of numbers,
and we don't have any decimal output. All numbers are given as hex
and we don't have any decimal output. All numbers are given as hex
numbers without a prefix (the only exception to this rule are the
numbers without a prefix (the only exception to this rule are the
numbers of registers proper, of course, which are given in decimal).
numbers of registers proper, of course, which are given in decimal).
The instructions which do sign extension show their arguments as
The instructions which do sign extension show their arguments as
signed hex numbers. Labels are also no longer prefixed.
signed hex numbers. Labels are also no longer prefixed.
Inline assembler completed.
Inline assembler completed.
17-Feb-2003
17-Feb-2003
ECO32 Version 0.2 released.
ECO32 Version 0.2 released.
20-Aug-2003
20-Aug-2003
ECO32 Version 0.3 released.
ECO32 Version 0.3 released.
21-Aug-2003
21-Aug-2003
1) I changed the 'ldhi' opcode from 0x1E to 0x1F.
1) I changed the 'ldhi' opcode from 0x1E to 0x1F.
   Reason: The instruction decoding gets more regular.
   Reason: The instruction decoding gets more regular.
2) The ALU has now an 'xnor' instruction instead of a 'nor':
2) The ALU has now an 'xnor' instruction instead of a 'nor':
   (a xnor b) = ~(a ^ b) = (~a ^ b) = (a ^ ~b) = (a == b),
   (a xnor b) = ~(a ^ b) = (~a ^ b) = (a ^ ~b) = (a == b),
   bitwise parallel for all 32 bits.
   bitwise parallel for all 32 bits.
   Reason: The ALU is easier to implement, and the instruction
   Reason: The ALU is easier to implement, and the instruction
   set becomes more regular.
   set becomes more regular.
3) The PC relative jumps (j, jal, all conditional branches) now
3) The PC relative jumps (j, jal, all conditional branches) now
   have PC+4 as their reference location (and no longer PC).
   have PC+4 as their reference location (and no longer PC).
   Reason: PC+4 is computed early in the instruction cycle; all
   Reason: PC+4 is computed early in the instruction cycle; all
   other RISC machines do this alike.
   other RISC machines do this alike.
4) The PC relative jumps (j, jal, all conditional branches) now
4) The PC relative jumps (j, jal, all conditional branches) now
   encode a word offset, and no longer a byte offset.
   encode a word offset, and no longer a byte offset.
   Reason: The target ranges for the jumps are quadrupled without
   Reason: The target ranges for the jumps are quadrupled without
   any additional effort.
   any additional effort.
07-Oct-2003
07-Oct-2003
Explored the possibilities to implement a graphics controller for
Explored the possibilities to implement a graphics controller for
ECO32. Easy from the simulator's point of view, not quite so easy
ECO32. Easy from the simulator's point of view, not quite so easy
from the implementer's point of view (due to X complications,
from the implementer's point of view (due to X complications,
threads needed) but certainly feasible.
threads needed) but certainly feasible.
13-Oct-2003
13-Oct-2003
Graphics controller implemented.
Graphics controller implemented.
20-Oct-2003
20-Oct-2003
Curses feeds certain keypad codes directly into the simulator's
Curses feeds certain keypad codes directly into the simulator's
terminal, e.g. KEY_BACKSPACE. There the MSBs get stripped off and
terminal, e.g. KEY_BACKSPACE. There the MSBs get stripped off and
a wrong keycode is supplied to the simulated program. Now these
a wrong keycode is supplied to the simulated program. Now these
special codes are mapped to regular control characters, e.g. BS.
special codes are mapped to regular control characters, e.g. BS.
25-Oct-2003
25-Oct-2003
The assembler now understands the option '-h' which suppresses the
The assembler now understands the option '-h' which suppresses the
output of the executable's header and appends the BSS's size bytes
output of the executable's header and appends the BSS's size bytes
of zeroes at the end of the executable. This in turn renders the
of zeroes at the end of the executable. This in turn renders the
'load' tool redundant, which can be deleted. Done.
'load' tool redundant, which can be deleted. Done.
26-Oct-2003
26-Oct-2003
A group of students is working on a ROM-based monitor program. They
A group of students is working on a ROM-based monitor program. They
need an instruction to implement breakpoints. Because the instruction
need an instruction to implement breakpoints. Because the instruction
map is already crowded they have to use 'trap'. But they want of
map is already crowded they have to use 'trap'. But they want of
course a breakpoint trap be easily distinguishable from any other
course a breakpoint trap be easily distinguishable from any other
kind of trap. So the assembler now allows a constant operand for
kind of trap. So the assembler now allows a constant operand for
'trap'. This operand is assembled into the otherwise unused bits
'trap'. This operand is assembled into the otherwise unused bits
of the instruction. These bits are in turn ignored by the CPU (as
of the instruction. These bits are in turn ignored by the CPU (as
was the case all the time) but can be inspected by software which
was the case all the time) but can be inspected by software which
must read the instruction from memory in order to do this. Now a
must read the instruction from memory in order to do this. Now a
breakpoint trap can get a unique bit pattern distinct from the bit
breakpoint trap can get a unique bit pattern distinct from the bit
patterns of all other traps. Remark: not only the regular assembler
patterns of all other traps. Remark: not only the regular assembler
must understand this but also the simulator's inline assembler as
must understand this but also the simulator's inline assembler as
well as its disassembler. Done.
well as its disassembler. Done.
09-Nov-2003
09-Nov-2003
The curses library correctly sets the terminal mode to "raw" so that
The curses library correctly sets the terminal mode to "raw" so that
neither SIGINT nor SIGQUIT signals can be generated by the keyboard.
neither SIGINT nor SIGQUIT signals can be generated by the keyboard.
With a graphics controller attached it is however possible that the
With a graphics controller attached it is however possible that the
user selects "kill" from the window menu of the monitor window and
user selects "kill" from the window menu of the monitor window and
thus shuts down the connection to the X server. This in turn leads
thus shuts down the connection to the X server. This in turn leads
to an uncontrolled instant termination of the whole simulator which
to an uncontrolled instant termination of the whole simulator which
cannot be tolerated (e.g. the terminal would stay in raw mode: very
cannot be tolerated (e.g. the terminal would stay in raw mode: very
annoying for an unsuspecting user). Solution: install an I/O error
annoying for an unsuspecting user). Solution: install an I/O error
handler which gets called from the X system in case the connection
handler which gets called from the X system in case the connection
to the server is lost. Done.
to the server is lost. Done.
16-Nov-2003
16-Nov-2003
I added a check to the initialization of the memory simulation ensuring
I added a check to the initialization of the memory simulation ensuring
that neither ROM image files nor program files loaded into main memory
that neither ROM image files nor program files loaded into main memory
can overflow the available space (and thus crash the simulator).
can overflow the available space (and thus crash the simulator).
18-Nov-2003
18-Nov-2003
The terminal simulation now handles the following control characters:
The terminal simulation now handles the following control characters:
(input)             0x0D
(input)             0x0D
                 0x08
                 0x08
                0x0E
                0x0E
                  0x10
                  0x10
                0x02
                0x02
               0x06
               0x06
(output)   0x07             beep
(output)   0x07             beep
           0x0D             return cursor to begin of current line
           0x0D             return cursor to begin of current line
           0x0A             scroll if cursor is in last line,
           0x0A             scroll if cursor is in last line,
                            set cursor to next line in same column
                            set cursor to next line in same column
           0x02             move cursor left (stop at leftmost column)
           0x02             move cursor left (stop at leftmost column)
           0x06             move cursor right (stop at rightmost column)
           0x06             move cursor right (stop at rightmost column)
           0x10             move cursor up (stop at topmost line)
           0x10             move cursor up (stop at topmost line)
           0x0E             move cursor down (stop at bottom line)
           0x0E             move cursor down (stop at bottom line)
           0x08             delete character to the left of cursor,
           0x08             delete character to the left of cursor,
                            move cursor left
                            move cursor left
           0x09             output spaces (minimum is one space),
           0x09             output spaces (minimum is one space),
                            until column mod 8 = 0
                            until column mod 8 = 0
19-Nov-2003
19-Nov-2003
Today I took the first few steps towards a bootable system disk.
Today I took the first few steps towards a bootable system disk.
Changes in bootstrap monitor:
Changes in bootstrap monitor:
  - 'g' command deleted
  - 'g' command deleted
  - monitor stack sits just below 1M
  - monitor stack sits just below 1M
  - master boot record loaded at physical address 0x00000000
  - master boot record loaded at physical address 0x00000000
  - master boot record started at virtual address 0xC0000000
  - master boot record started at virtual address 0xC0000000
Changes in constructing the default master boot record:
Changes in constructing the default master boot record:
  - relocate code to 0xC0000000
  - relocate code to 0xC0000000
20-Nov-2003
20-Nov-2003
Now here is the big picture of the boot process:
Now here is the big picture of the boot process:
a) ROM bootstrap
a) ROM bootstrap
   The ROM loads the first sector of the disk and starts whatever it
   The ROM loads the first sector of the disk and starts whatever it
   has loaded (provided that the signature is present). Until now this
   has loaded (provided that the signature is present). Until now this
   was always the default master boot record. In the future this will
   was always the default master boot record. In the future this will
   be the first stage bootstrap. This part is already finished.
   be the first stage bootstrap. This part is already finished.
b) First stage bootstrap
b) First stage bootstrap
   The first stage looks for a file named "boot" in the root directory
   The first stage looks for a file named "boot" in the root directory
   of the file system on the boot disk. This part must fit into a single
   of the file system on the boot disk. This part must fit into a single
   sector and thus is restricted in its capabilities:
   sector and thus is restricted in its capabilities:
     - boot must lie in the root directoy
     - boot must lie in the root directoy
     - it must be one of the first 320 directory entries in the root
     - it must be one of the first 320 directory entries in the root
       directory (only the 10 direct blocks of the directory file are
       directory (only the 10 direct blocks of the directory file are
       searched for it)
       searched for it)
     - it must not be bigger than 5120 Bytes (only the 10 direct blocks
     - it must not be bigger than 5120 Bytes (only the 10 direct blocks
       of the executable file are loaded)
       of the executable file are loaded)
c) Second stage bootstrap
c) Second stage bootstrap
   This stage loads the kernel, perhaps asking the user for its name.
   This stage loads the kernel, perhaps asking the user for its name.
22-Nov-2003
22-Nov-2003
First stage bootstrap completed.
First stage bootstrap completed.
27-Nov-2003
27-Nov-2003
Second stage bootstrap completed.
Second stage bootstrap completed.
It was indeed possible to ask the user for the path to the kernel he
It was indeed possible to ask the user for the path to the kernel he
wants to get started. The only kernel available for now is one of the
wants to get started. The only kernel available for now is one of the
tests from tst/os.
tests from tst/os.
29-Nov-2003
29-Nov-2003
Makefiles tweaked.
Makefiles tweaked.
06-Dec-2003
06-Dec-2003
Today I started to develop the tools shfs and mkfs for file systems
Today I started to develop the tools shfs and mkfs for file systems
with 4K blocksize. With this blocksize it should be possible to do
with 4K blocksize. With this blocksize it should be possible to do
the bootstrap without a named second stage. Conceptually there are
the bootstrap without a named second stage. Conceptually there are
again two stages (first load a single sector, then the rest), but
again two stages (first load a single sector, then the rest), but
both stages should fit within the boot block.
both stages should fit within the boot block.
20-Dec-2003
20-Dec-2003
I discovered a small bug (?) in the simulator: if a write to $0 is
I discovered a small bug (?) in the simulator: if a write to $0 is
requested by an instruction, not only the write is suppressed (this
requested by an instruction, not only the write is suppressed (this
is expected) but also the source operand does not get computed.
is expected) but also the source operand does not get computed.
Thus the instruction ldw $0,$0,1 which is incorrect if no TLB entry
Thus the instruction ldw $0,$0,1 which is incorrect if no TLB entry
for page 0 exists (and is so even if it exists because of alignment
for page 0 exists (and is so even if it exists because of alignment
violation) does not lead to an exception (which is quite unexpected).
violation) does not lead to an exception (which is quite unexpected).
Solution: Always compute the source operands, even if $0 is the target.
Solution: Always compute the source operands, even if $0 is the target.
30-Dec-2003
30-Dec-2003
In order to use swap space on the same disk where the root file system
In order to use swap space on the same disk where the root file system
is located we need some form of disk partitioning, preferrably NOT
is located we need some form of disk partitioning, preferrably NOT
deeply coded into the disk driver (as the original UNIX has done it).
deeply coded into the disk driver (as the original UNIX has done it).
In other words, we need a real master boot record, a partition table
In other words, we need a real master boot record, a partition table
and a tool ("fdisk" or "mkpart") to set up such a table.
and a tool ("fdisk" or "mkpart") to set up such a table.
01-Jan-2004
01-Jan-2004
"mkpart" finished. It constructs a partition table from a textual
"mkpart" finished. It constructs a partition table from a textual
configuration file and writes it to sector 1. It also copies an MBR
configuration file and writes it to sector 1. It also copies an MBR
(which has not been done yet) to sector 0, and a bootstrap manager
(which has not been done yet) to sector 0, and a bootstrap manager
(which also has yet to be done) to sectors 2-7.
(which also has yet to be done) to sectors 2-7.
MBR coded.
MBR coded.
02-Jan-2004
02-Jan-2004
Bootstrap manager done.
Bootstrap manager done.
03-Jan-2004
03-Jan-2004
Tool "mkpart" is working.
Tool "mkpart" is working.
New tool "shpart" displays a partition table, read from a disk image.
New tool "shpart" displays a partition table, read from a disk image.
04-Jan-2004
04-Jan-2004
I made the file systen viewer aware of partitions.
I made the file systen viewer aware of partitions.
05-Jan-2004
05-Jan-2004
Now "mkfs" also knows something about partitions.
Now "mkfs" also knows something about partitions.
08-Jan-2004
08-Jan-2004
If the operating system is booted from a partition of a disk (in
If the operating system is booted from a partition of a disk (in
contrast to being booted from the start of the whole disk) its disk
contrast to being booted from the start of the whole disk) its disk
driver must know where logical sector 0 of the partition is located
driver must know where logical sector 0 of the partition is located
on the disk. In other words, the master bootstrap must transfer a
on the disk. In other words, the master bootstrap must transfer a
little bit of information to the boot loader of the OS. This could
little bit of information to the boot loader of the OS. This could
be done as follows: $26 holds the start sector of the partition from
be done as follows: $26 holds the start sector of the partition from
where the OS is booted and $27 holds its size. In order to use the
where the OS is booted and $27 holds its size. In order to use the
very same bootstrap also in the case that the disk has no partitions
very same bootstrap also in the case that the disk has no partitions
(and thus the file system occupies the whole disk), this information
(and thus the file system occupies the whole disk), this information
must also be supplied by the ROM bootstrap sequence. Done.
must also be supplied by the ROM bootstrap sequence. Done.
Surprise: this scheme would allow the sub-partitioning of a partition
Surprise: this scheme would allow the sub-partitioning of a partition
without any modification!
without any modification!
10-Jan-2004
10-Jan-2004
Now the whole bootstrap chain is working. It goes like this:
Now the whole bootstrap chain is working. It goes like this:
a) The ROM loads the first sector of the disk and starts whatever it
a) The ROM loads the first sector of the disk and starts whatever it
   has loaded (provided that the 0x55AA signature is present). This
   has loaded (provided that the 0x55AA signature is present). This
   may be either the master boot record if the disk is partitioned,
   may be either the master boot record if the disk is partitioned,
   or an ordinary boot record if it is not (see remark below).
   or an ordinary boot record if it is not (see remark below).
b) In case the master boot record is executing, it loads sectors 2..7
b) In case the master boot record is executing, it loads sectors 2..7
   into memory (sector 1, the second sector of the disk, is skipped
   into memory (sector 1, the second sector of the disk, is skipped
   because it holds the partition table). These sectors contain a small
   because it holds the partition table). These sectors contain a small
   program, the boot manager, in executable format. The boot manager is
   program, the boot manager, in executable format. The boot manager is
   started by the master boot record.
   started by the master boot record.
c) The boot manager loads the partition table from sector 1 of the disk,
c) The boot manager loads the partition table from sector 1 of the disk,
   displays the partitions of the disk, and asks the user to enter a
   displays the partitions of the disk, and asks the user to enter a
   partition number to boot. An attempt to boot a partition outside the
   partition number to boot. An attempt to boot a partition outside the
   range 0..15 is rejected, as well as requesting to boot a partition
   range 0..15 is rejected, as well as requesting to boot a partition
   which does not contain a file system of any kind, or does not have
   which does not contain a file system of any kind, or does not have
   the "bootable" flag set. If all is well, the boot record of the
   the "bootable" flag set. If all is well, the boot record of the
   selected partition is loaded. If it has a valid 0x55AA signature,
   selected partition is loaded. If it has a valid 0x55AA signature,
   it is started.
   it is started.
   Remark: This is the point in the bootstrap chain which is reached
   Remark: This is the point in the bootstrap chain which is reached
   immediately from the ROM code if the disk is not partitioned.
   immediately from the ROM code if the disk is not partitioned.
d) The boot record code loads partition relative sectors 1..7, i.e.
d) The boot record code loads partition relative sectors 1..7, i.e.
   the rest of the boot block. These sectors contain a small program,
   the rest of the boot block. These sectors contain a small program,
   the bootstrap loader, in executable format. The bootstrap loader is
   the bootstrap loader, in executable format. The bootstrap loader is
   started by the boot record code.
   started by the boot record code.
e) The bootstrap loader asks the user for a path to a file which must
e) The bootstrap loader asks the user for a path to a file which must
   exist, must be a regular file, and must be executable by its owner.
   exist, must be a regular file, and must be executable by its owner.
   This will of course be normally an operating system kernel. The
   This will of course be normally an operating system kernel. The
   default value is /boot/unix. The file is loaded and started.
   default value is /boot/unix. The file is loaded and started.
Throughout the whole process registers $26 and $27 hold the start sector
Throughout the whole process registers $26 and $27 hold the start sector
and size of the currently selected range of the disk, respectively.
and size of the currently selected range of the disk, respectively.
12-Jan-2004
12-Jan-2004
The register conventions shown above must be changed somewhat because
The register conventions shown above must be changed somewhat because
with more than one disk present it is also necessary to tell the disk
with more than one disk present it is also necessary to tell the disk
driver which disk to use:
driver which disk to use:
$26 base address of disk controller
$26 base address of disk controller
$27 start sector of partition (or disk)
$27 start sector of partition (or disk)
$28 size of partition (or disk) in sectors
$28 size of partition (or disk) in sectors
28-Jan-2004
28-Jan-2004
After rewriting parts of the make file system utility (so that double
After rewriting parts of the make file system utility (so that double
indirect blocks can be used, which is necessary for a file system with
indirect blocks can be used, which is necessary for a file system with
512 byte blocks to hold files of more than 69K) it is now possible to
512 byte blocks to hold files of more than 69K) it is now possible to
boot our port of UNIX 7th Edition from the disk. Alas, it is not yet
boot our port of UNIX 7th Edition from the disk. Alas, it is not yet
running very stable.
running very stable.
10-Mar-2004
10-Mar-2004
Finally I added the generation of copying loops to the compiler's
Finally I added the generation of copying loops to the compiler's
back-end. This has long been missing.
back-end. This has long been missing.
17-Apr-2004
17-Apr-2004
Translating virtual addresses using the TLB costs time because the
Translating virtual addresses using the TLB costs time because the
parallel associative hardware must be simulated by serial software.
parallel associative hardware must be simulated by serial software.
This is very noticeable with programs running in user mode; they run
This is very noticeable with programs running in user mode; they run
at roughly one third of the speed kernel mode programs do. In order
at roughly one third of the speed kernel mode programs do. In order
to alleviate this I added a function which acts almost the same as
to alleviate this I added a function which acts almost the same as
the TLB associative lookup does, but without any error checks. Its
the TLB associative lookup does, but without any error checks. Its
sole pupose is to use up time and it is called whenever an unmapped
sole pupose is to use up time and it is called whenever an unmapped
address is detected by the virtual-to-physical address translation.
address is detected by the virtual-to-physical address translation.
21-Apr-2004
21-Apr-2004
Up till now the assembler located the data segment directly above
Up till now the assembler located the data segment directly above
the code segment. This is not a viable strategy once paging is in
the code segment. This is not a viable strategy once paging is in
effect. Due to code sharing and protection reasons, the data segment
effect. Due to code sharing and protection reasons, the data segment
should start on the next page boundary above the code. The resulting
should start on the next page boundary above the code. The resulting
gap may also be present in the executable file: there is no need to
gap may also be present in the executable file: there is no need to
store any bytes for it in the executable (at least as long as it is
store any bytes for it in the executable (at least as long as it is
an executable with a header - for headerless executables the gap
an executable with a header - for headerless executables the gap
bytes must be stored within the file).
bytes must be stored within the file).
It would have been possible to define two different executable formats,
It would have been possible to define two different executable formats,
one with the data segment directly following the code segment, and
one with the data segment directly following the code segment, and
another one with the data segment aligned on a page boundary. The
another one with the data segment aligned on a page boundary. The
two formats then would have to be distinguished by different magic
two formats then would have to be distinguished by different magic
numbers in the header. I did not do this, however, because I saw
numbers in the header. I did not do this, however, because I saw
no reason to keep the "directly following" format. If one wants to
no reason to keep the "directly following" format. If one wants to
compress code and data as much as possible, one can in any case put
compress code and data as much as possible, one can in any case put
both into the code segment.
both into the code segment.
24-Apr-2004
24-Apr-2004
The simulated graphics device did not detect memory accesses which
The simulated graphics device did not detect memory accesses which
lie within the device address bounds but outside the screen memory.
lie within the device address bounds but outside the screen memory.
These accesses were propagated to the X Window System and in turn an
These accesses were propagated to the X Window System and in turn an
X Window data structure was accessed outside of its allocated memory.
X Window data structure was accessed outside of its allocated memory.
At least on our Sun computer this translated to an immediate death
At least on our Sun computer this translated to an immediate death
of the simulator process. Now the graphics device detects such an
of the simulator process. Now the graphics device detects such an
attempt to access simulated memory outside the screen, and produces
attempt to access simulated memory outside the screen, and produces
a 'bus timeout' exception.
a 'bus timeout' exception.
06-May-2004
06-May-2004
ECO32 Version 0.4 released.
ECO32 Version 0.4 released.
08-May-2004
08-May-2004
I intend to give the ECO32 simulator the ability to run with more than
I intend to give the ECO32 simulator the ability to run with more than
one simulated terminal. This will work best if there is no difference
one simulated terminal. This will work best if there is no difference
between the first terminal and the other ones, so I will open a separate
between the first terminal and the other ones, so I will open a separate
window for each terminal (and use the first window in which the simulator
window for each terminal (and use the first window in which the simulator
was started only for controlling the simulator, and NOT for a simulated
was started only for controlling the simulator, and NOT for a simulated
terminal). Then using curses is no longer necessary and can be removed.
terminal). Then using curses is no longer necessary and can be removed.
But I want to retain command line editing, so I will use the 'getline'
But I want to retain command line editing, so I will use the 'getline'
library.
library.
Curses interface removed.
Curses interface removed.
Getline library installed.
Getline library installed.
Interrupt priorities changed:
Interrupt priorities changed:
  15    not used
  15    not used
  14    timer
  14    timer
  13    not used
  13    not used
  12    not used
  12    not used
  11    not used
  11    not used
  10    not used
  10    not used
  09    not used
  09    not used
  08    disk
  08    disk
  07    terminal 3 receiver
  07    terminal 3 receiver
  06    terminal 3 transmitter
  06    terminal 3 transmitter
  05    terminal 2 receiver
  05    terminal 2 receiver
  04    terminal 2 transmitter
  04    terminal 2 transmitter
  03    terminal 1 receiver
  03    terminal 1 receiver
  02    terminal 1 transmitter
  02    terminal 1 transmitter
  01    terminal 0 receiver
  01    terminal 0 receiver
  00    terminal 0 transmitter
  00    terminal 0 transmitter
10-May-2004
10-May-2004
SIGINT handler installed (for use within the control window to regain
SIGINT handler installed (for use within the control window to regain
control in case of a runaway program).
control in case of a runaway program).
In order to use a single timer callback routine for all terminals, the
In order to use a single timer callback routine for all terminals, the
callback routine must get an argument, telling which terminal is doing
callback routine must get an argument, telling which terminal is doing
the callback. So ALL timer callbacks now have such an argument, which
the callback. So ALL timer callbacks now have such an argument, which
can be used arbitrarily by the callback initiator to communicate an
can be used arbitrarily by the callback initiator to communicate an
integer to the callback routine.
integer to the callback routine.
17-May-2004
17-May-2004
The new terminal implementation must be tested as well as the changed
The new terminal implementation must be tested as well as the changed
interrupt priority scheme. And even more important: allocation of the
interrupt priority scheme. And even more important: allocation of the
data segment on a page boundary (see 21-Apr-2004) must be verified!
data segment on a page boundary (see 21-Apr-2004) must be verified!
Done for the 'tst' directory.
Done for the 'tst' directory.
18-May-2004
18-May-2004
Done for the 'eos' directory.
Done for the 'eos' directory.
27-Feb-2005
27-Feb-2005
ECO32 Version 0.5 released.
ECO32 Version 0.5 released.
28-Feb-2005
28-Feb-2005
Despite the long time since the release of the previous version this
Despite the long time since the release of the previous version this
was very premature: I did not read the comments above and forgot to
was very premature: I did not read the comments above and forgot to
conduct many of the tests. And indeed, the bootstrap does not work
conduct many of the tests. And indeed, the bootstrap does not work
any longer.
any longer.
01-Mar-2005
01-Mar-2005
The bootstrap manager should not be compiled to any standard executable
The bootstrap manager should not be compiled to any standard executable
format, because this part of the boot process is independent of any
format, because this part of the boot process is independent of any
operating system. It should be compiled to plain binary format, as is
operating system. It should be compiled to plain binary format, as is
the master boot record. Now we are facing a dilemma: We want to write
the master boot record. Now we are facing a dilemma: We want to write
the boot manager (mostly) in C and therefore will have a separate data
the boot manager (mostly) in C and therefore will have a separate data
segment, aligned on a page boundary. But we also want a headerless
segment, aligned on a page boundary. But we also want a headerless
binary output, so there will be no loading information. All gaps in
binary output, so there will be no loading information. All gaps in
the loaded program and data will therefore be filled with zeroes.
the loaded program and data will therefore be filled with zeroes.
Then either we must define another executable format in which the data
Then either we must define another executable format in which the data
segment follows directly after the code segment (without padding to the
segment follows directly after the code segment (without padding to the
next page boundary, see discussion above) or we have to spend somewhat
next page boundary, see discussion above) or we have to spend somewhat
more space on disk for the bootstrap managers's program/data image.
more space on disk for the bootstrap managers's program/data image.
I think I will do the latter.
I think I will do the latter.
04-Mar-2005
04-Mar-2005
The solution above is not very elegant: The same reasoning applies also
The solution above is not very elegant: The same reasoning applies also
to the bootstrap within a partition. Then we are forced to reserve two
to the bootstrap within a partition. Then we are forced to reserve two
blocks instead of the traditional single one for the bootstrap. This is
blocks instead of the traditional single one for the bootstrap. This is
not totally out of question, but not very appealing either.
not totally out of question, but not very appealing either.
There is another solution, if we accept the boot manager to be compiled
There is another solution, if we accept the boot manager to be compiled
to standard executable format: write a very compact loader for this format
to standard executable format: write a very compact loader for this format
and squeeze it into the master boot record. Difficult, but it can be
and squeeze it into the master boot record. Difficult, but it can be
done, as I proved today.
done, as I proved today.
Changes from above reverted.
Changes from above reverted.
Disk partitioning, master boot record, and boot manager done.
Disk partitioning, master boot record, and boot manager done.
05-Mar-2005
05-Mar-2005
Boot record and bootstrap loader done.
Boot record and bootstrap loader done.
08-Mar-2005
08-Mar-2005
I think that today I completed the tests and changes which I begun
I think that today I completed the tests and changes which I begun
on 17-May-2004.
on 17-May-2004.
ECO32 Version 0.6 released.
ECO32 Version 0.6 released.
27-Oct-2005
27-Oct-2005
ECO32 Version 0.7 released.
ECO32 Version 0.7 released.
This was done in order to have a stable release on which to build
This was done in order to have a stable release on which to build
a simplified version of the ECO32, which is named ECO32e (the 'e'
a simplified version of the ECO32, which is named ECO32e (the 'e'
stands for 'embedded'). The ECO32e will get implemented in an FPGA.
stands for 'embedded'). The ECO32e will get implemented in an FPGA.
26-Jun-2006
26-Jun-2006
We do have an error in the implementation of the SAR instructions,
We do have an error in the implementation of the SAR instructions,
really! The C standard says that the result of shifts with shift
really! The C standard says that the result of shifts with shift
amounts greater than or equal to (!) the number of bits in the left
amounts greater than or equal to (!) the number of bits in the left
expression's type is undefined. Consequently, in the CPU implementation
expression's type is undefined. Consequently, in the CPU implementation
cpu.c we have to replace
cpu.c we have to replace
smsk = (MSB ? 0xFFFFFFFF << (32 - scnt) : 0);
smsk = (MSB ? 0xFFFFFFFF << (32 - scnt) : 0);
in the SAR and SARI instructions with
in the SAR and SARI instructions with
smsk = (MSB ? ~(((Word) 0xFFFFFFFF) >> scnt) : 0);
smsk = (MSB ? ~(((Word) 0xFFFFFFFF) >> scnt) : 0);
because if scnt == 0 then 0xFFFFFFFF << (32 - scnt) is undefined.
because if scnt == 0 then 0xFFFFFFFF << (32 - scnt) is undefined.
Thanks to Rolf Viehmann for pointing this out.
Thanks to Rolf Viehmann for pointing this out.
27-Jun-2006
27-Jun-2006
The rfx instruction must not be executed in user mode, because it
The rfx instruction must not be executed in user mode, because it
writes the previous mode and interrupt enable bits of the PSW over
writes the previous mode and interrupt enable bits of the PSW over
the current ones. Therefore rfx becomes a privileged instruction
the current ones. Therefore rfx becomes a privileged instruction
which triggers EXC_PRV_INSTRCT if executed in user mode.
which triggers EXC_PRV_INSTRCT if executed in user mode.
Again thanks to Rolf Viehmann for recognizing the potential danger
Again thanks to Rolf Viehmann for recognizing the potential danger
if this instruction is executed in user mode.
if this instruction is executed in user mode.
09-Jul-2006
09-Jul-2006
Pending interrupts are now displayed when executing the 'register'
Pending interrupts are now displayed when executing the 'register'
command. It is not meaningful to display pending exceptions, however,
command. It is not meaningful to display pending exceptions, however,
because these are immediately handled within the longjump framework
because these are immediately handled within the longjump framework
and thus would never show anything else but 'off'.
and thus would never show anything else but 'off'.
10-Jul-2006
10-Jul-2006
We have a new command to display (and possibly change) the value of
We have a new command to display (and possibly change) the value of
the PSW. This comes in very handy if debugging in user mode and thus
the PSW. This comes in very handy if debugging in user mode and thus
not having access to privileged addresses.
not having access to privileged addresses.
12-Jul-2006
12-Jul-2006
There is a new control bit in the PSW, the 'vector bit' V, which directs
There is a new control bit in the PSW, the 'vector bit' V, which directs
interrupts to ROM_BASE + 4 if it is off and to RAM_BASE + 4 if it is on.
interrupts to ROM_BASE + 4 if it is off and to RAM_BASE + 4 if it is on.
This bit is cleared when the CPU is reset. In this way the software can
This bit is cleared when the CPU is reset. In this way the software can
decide whether the interrupt service routine is located in ROM or in RAM.
decide whether the interrupt service routine is located in ROM or in RAM.
15-Jul-2006
15-Jul-2006
I decided to give "user TLB misses" an extra interrupt service routine
I decided to give "user TLB misses" an extra interrupt service routine
entry point. These are TLB misses triggered by an access to a virtual
entry point. These are TLB misses triggered by an access to a virtual
address with MSB = 0, regardless of execution mode (user or kernel).
address with MSB = 0, regardless of execution mode (user or kernel).
22-Jul-2006
22-Jul-2006
The physical address space (2^30 bytes) is partitioned as follows
The physical address space (2^30 bytes) is partitioned as follows
(in order to be compatible with the ECO32e):
(in order to be compatible with the ECO32e):
RAM    virt start 0xC0000000    phys start 0x00000000    size 0x20000000
RAM    virt start 0xC0000000    phys start 0x00000000    size 0x20000000
ROM    virt start 0xE0000000    phys start 0x20000000    size 0x10000000
ROM    virt start 0xE0000000    phys start 0x20000000    size 0x10000000
I/O    virt start 0xF0000000    phys start 0x30000000    size 0x10000000
I/O    virt start 0xF0000000    phys start 0x30000000    size 0x10000000
The I/O address space is evenly divided into 256 devices which may
The I/O address space is evenly divided into 256 devices which may
occupy up to 1MByte each.
occupy up to 1MByte each.
30-Jul-2006
30-Jul-2006
We now have two control bits in the outgoing part of every entry of
We now have two control bits in the outgoing part of every entry of
the TLB: a "valid" bit (which triggers a "TLB invalid exception" if
the TLB: a "valid" bit (which triggers a "TLB invalid exception" if
this entry is selected by a memory translation and the bit is 0) and
this entry is selected by a memory translation and the bit is 0) and
a "write" bit (which triggers a "TLB write exception" if this entry
a "write" bit (which triggers a "TLB write exception" if this entry
is used to map a write access to a page and the bit is 0). The "TLB
is used to map a write access to a page and the bit is 0). The "TLB
double hit exception" does not exist any longer.
double hit exception" does not exist any longer.
The reason for existence of the "write" bit is obvious (possibility
The reason for existence of the "write" bit is obvious (possibility
to protect pages from writing, implement a copy-on-write policy).
to protect pages from writing, implement a copy-on-write policy).
The reason for existence of the "valid" bit is speed: the TLB refill
The reason for existence of the "valid" bit is speed: the TLB refill
routine should run as fast as possible and therefore should avoid
routine should run as fast as possible and therefore should avoid
tests for special cases as much as possible. If some processing must
tests for special cases as much as possible. If some processing must
be done for a page to be usable, the check for this condition should
be done for a page to be usable, the check for this condition should
not be done in the TLB miss handler. If the valid bit is cleared in
not be done in the TLB miss handler. If the valid bit is cleared in
the page table, the refill routine will enter the translation that it
the page table, the refill routine will enter the translation that it
gets from the page table into the TLB without checking, but the next
gets from the page table into the TLB without checking, but the next
use of this entry will lead to another exception, where the processing
use of this entry will lead to another exception, where the processing
then can be done.
then can be done.
31-Jul-2006
31-Jul-2006
The implementation of the ECO32e suggested a different coding of the
The implementation of the ECO32e suggested a different coding of the
single register operand in the jr and jalr instructions. It is now
single register operand in the jr and jalr instructions. It is now
coded in the src1 field instead of the dst field of these instructions.
coded in the src1 field instead of the dst field of these instructions.
01-Aug-2006
01-Aug-2006
a) I rearranged the exceptions as follows:
a) I rearranged the exceptions as follows:
EXC_BUS_TIMEOUT 16
EXC_BUS_TIMEOUT 16
EXC_ILL_INSTRCT 17
EXC_ILL_INSTRCT 17
EXC_PRV_INSTRCT 18
EXC_PRV_INSTRCT 18
EXC_DIVIDE      19
EXC_DIVIDE      19
EXC_TRAP        20
EXC_TRAP        20
EXC_TLB_MISS    21
EXC_TLB_MISS    21
EXC_TLB_WRITE   22
EXC_TLB_WRITE   22
EXC_TLB_INVALID 23
EXC_TLB_INVALID 23
EXC_ILL_ADDRESS 24
EXC_ILL_ADDRESS 24
EXC_PRV_ADDRESS 25
EXC_PRV_ADDRESS 25
In this way they are grouped together more logically.
In this way they are grouped together more logically.
b) The detection of an EXC_ILL_ADDRESS exception (formerly called
b) The detection of an EXC_ILL_ADDRESS exception (formerly called
EXC_BUS_ADDRESS) is now done in the MMU and thus operates on logical
EXC_BUS_ADDRESS) is now done in the MMU and thus operates on logical
addresses. It is then possible to store the offending address in the
addresses. It is then possible to store the offending address in the
BadAddr register for further processing by OS software.
BadAddr register for further processing by OS software.
c) The EntryHi register now gets loaded with the page base address
c) The EntryHi register now gets loaded with the page base address
if one of the three TLB exceptions occurs, so that it need not be
if one of the three TLB exceptions occurs, so that it need not be
computed from the contents of the BadAddr register.
computed from the contents of the BadAddr register.
02-Aug-2006
02-Aug-2006
A "context" register, which is preloaded by OS software with the base
A "context" register, which is preloaded by OS software with the base
address of memory-resident page tables, and where the page number of
address of memory-resident page tables, and where the page number of
a page with missing translation is ored-in by hardware would speed up
a page with missing translation is ored-in by hardware would speed up
the TLB miss handler. On the other hand, it practically mandates the
the TLB miss handler. On the other hand, it practically mandates the
use of a certain page table format (or, if the OS designer wants a
use of a certain page table format (or, if the OS designer wants a
different format, the context register would not be used at all).
different format, the context register would not be used at all).
Therefore I will not implement a context register.
Therefore I will not implement a context register.
03-Oct-2006
03-Oct-2006
Major instruction format redesign: the decision to put the destination
Major instruction format redesign: the decision to put the destination
register address in a fixed location within the instruction was wrong.
register address in a fixed location within the instruction was wrong.
It implied that the source register addresses were not fixed and thus
It implied that the source register addresses were not fixed and thus
must be multiplexed early in the instruction cycle dependent upon the
must be multiplexed early in the instruction cycle dependent upon the
opcode. It should be done the other way around. Completed.
opcode. It should be done the other way around. Completed.
19-Nov-2006
19-Nov-2006
Today I completed the back-port of the display and keyboard from ECO32e.
Today I completed the back-port of the display and keyboard from ECO32e.
Both are available if the command line switch -c ("console") is given.
Both are available if the command line switch -c ("console") is given.
The default number of terminals was in turn reduced to 0.
The default number of terminals was in turn reduced to 0.
14-Feb-2007
14-Feb-2007
Interrupts are now level triggered. If at any time interrupt sharing
Interrupts are now level triggered. If at any time interrupt sharing
would become necessary (this is in fact quite possible with only 16
would become necessary (this is in fact quite possible with only 16
interrupts) it cannot be realized if interrupts were edge triggered.
interrupts) it cannot be realized if interrupts were edge triggered.
04-Jun-2008
04-Jun-2008
Project finally split:
Project finally split:
ECO32 (version 0.17) -- FPGA hardware, simulator, assembler
ECO32 (version 0.17) -- FPGA hardware, simulator, assembler
EOS32 (version 0.11) -- C compiler, ROM monitor, operating system
EOS32 (version 0.11) -- C compiler, ROM monitor, operating system
20-Feb-2009
20-Feb-2009
ECO32 now has its own linkable object file format, which is a variant
ECO32 now has its own linkable object file format, which is a variant
of the venerable a.out format. Consequently, 'asld' has been split into
of the venerable a.out format. Consequently, 'asld' has been split into
the assembler 'as' and the linking loader 'ld'. Additionally, there is
the assembler 'as' and the linking loader 'ld'. Additionally, there is
a program 'dof' which dumps the contents of an object file.
a program 'dof' which dumps the contents of an object file.
22-Feb-2009
22-Feb-2009
What is the exact meaning of 'jalr $31'? This can of course be defined
What is the exact meaning of 'jalr $31'? This can of course be defined
arbitrarily, but the natural semantics would likely be "jump to the
arbitrarily, but the natural semantics would likely be "jump to the
routine addressed by $31 and remember the return address (in $31)".
routine addressed by $31 and remember the return address (in $31)".
To my surprise, the hardware did exactly that, while the simulator
To my surprise, the hardware did exactly that, while the simulator
interpreted the instruction as "store the return address in $31 and
interpreted the instruction as "store the return address in $31 and
then jump to the routine addressed by $31", which resulted in not
then jump to the routine addressed by $31", which resulted in not
taking the jump at all. Simulator corrected.
taking the jump at all. Simulator corrected.
14-Feb-2011
14-Feb-2011
B_PHYS and B_MAP macros eliminated. They both are only used with the
B_PHYS and B_MAP macros eliminated. They both are only used with the
PDP-11 UNIBUS map functionality.
PDP-11 UNIBUS map functionality.
15-Feb-2011
15-Feb-2011
In the simulated ECO32, if I try to allocate 60 chunks of memory, each
In the simulated ECO32, if I try to allocate 60 chunks of memory, each
of them having 10000 bytes, I get a kernel panic: exception 22 in kernel
of them having 10000 bytes, I get a kernel panic: exception 22 in kernel
mode. The reason is untested code, executed for the first time ever: the
mode. The reason is untested code, executed for the first time ever: the
kernel is doing an "expansion swap" in order to get enough memory for
kernel is doing an "expansion swap" in order to get enough memory for
the process.
the process.
16-Feb-2011
16-Feb-2011
Now this is interesting: what is the field "b_bcount" in struct buf
Now this is interesting: what is the field "b_bcount" in struct buf
(include/buf.h) good for? Do any transfers with b_bcount != BSIZE
(include/buf.h) good for? Do any transfers with b_bcount != BSIZE
exist? The answer is yes, in two places:
exist? The answer is yes, in two places:
a) swap I/O (src/bio.c)
a) swap I/O (src/bio.c)
b) raw I/O (src/bio.c)
b) raw I/O (src/bio.c)
(There is a third (mis-)usage of the field b_bcount: it is used as
(There is a third (mis-)usage of the field b_bcount: it is used as
b_active flag in some block device drivers.)
b_active flag in some block device drivers.)
Raw I/O has to be overhauled in any case, so we concentrate on swap
Raw I/O has to be overhauled in any case, so we concentrate on swap
I/O here. Swap I/O transfers possibly many pages at once, starting
I/O here. Swap I/O transfers possibly many pages at once, starting
at a given disk block and a given memory address. But this is only
at a given disk block and a given memory address. But this is only
correct under the current "contiguous physical memory per process"
correct under the current "contiguous physical memory per process"
allocation policy. It is useless under any policy which allocates
allocation policy. It is useless under any policy which allocates
physical memory for a process non-contiguously - provided that the
physical memory for a process non-contiguously - provided that the
transfer mechanism accesses physical memory and not virtual memory
transfer mechanism accesses physical memory and not virtual memory
(this is typically the case with DMA). So the kernel will no longer
(this is typically the case with DMA). So the kernel will no longer
rely on the disk driver (and possibly the disk hardware) to transfer
rely on the disk driver (and possibly the disk hardware) to transfer
multiple blocks in a single call, but split them up into single block
multiple blocks in a single call, but split them up into single block
transfers. Done - the "expansion swap" is now running.
transfers. Done - the "expansion swap" is now running.
----------------------------------------------------------------
----------------------------------------------------------------
In the meantime...
In the meantime...
  - experiments with porting ECO32 to another FPGA board
  - experiments with porting ECO32 to another FPGA board
  - splitting the project (separating the OS part)
  - splitting the project (separating the OS part)
  - experiments with a pipelined version of ECO32
  - experiments with a pipelined version of ECO32
----------------------------------------------------------------
----------------------------------------------------------------
03-Feb-2014
03-Feb-2014
Project "ECO32" created on OpenCores, based on version eco32-0.22:
Project "ECO32" created on OpenCores, based on version eco32-0.22:
http://opencores.org/project,eco32
http://opencores.org/project,eco32
04-Feb-2014
04-Feb-2014
Main Makefile, lcc, docs, binutils, sim, and simtest added.
Main Makefile, lcc, docs, binutils, sim, and simtest added.
05-Feb-2014
05-Feb-2014
FPGA implementations, hwtests, monitor, disk and standalone
FPGA implementations, hwtests, monitor, disk and standalone
programs added.
programs added.
07-Feb-2014
07-Feb-2014
Release eco32-0.22 tagged.
Release eco32-0.22 tagged.
08-Feb-2014
08-Feb-2014
ECO32 manual added. It can now be generated from TeX sources.
ECO32 manual added. It can now be generated from TeX sources.
18-Feb-2014
18-Feb-2014
Several changes in the simulator:
Several changes in the simulator:
a) There are two independent identical timer/counters
a) There are two independent identical timer/counters
available, of course with different interrupts and I/O
available, of course with different interrupts and I/O
addresses (see below).
addresses (see below).
b) The timer/counters are readable, so that they can
b) The timer/counters are readable, so that they can
be used for short-time measurements. They count clock
be used for short-time measurements. They count clock
cycles (no pre-scaling any longer). This change will
cycles (no pre-scaling any longer). This change will
affect all programs which use the timer/counters.
affect all programs which use the timer/counters.
c) The simulation timing model is completely based on
c) The simulation timing model is completely based on
clock cycles (and does no longer tries to function in
clock cycles (and does no longer tries to function in
some sort of "real-time"). As there is no real clock
some sort of "real-time"). As there is no real clock
within the simulator, but the natural time unit is
within the simulator, but the natural time unit is
one instruction, the simulation time is incremented
one instruction, the simulation time is incremented
by the CPI value (clock cycles per instruction) every
by the CPI value (clock cycles per instruction) every
instruction. I measured the CPI value in the real ECO32
instruction. I measured the CPI value in the real ECO32
implementation: it's a horrible 18 cycles per instruction,
implementation: it's a horrible 18 cycles per instruction,
yielding an instruction rate of about 2.8 MIPS. There is
yielding an instruction rate of about 2.8 MIPS. There is
so much room for improvements...
so much room for improvements...
d) I changed the resolution of the simulation timers to
d) I changed the resolution of the simulation timers to
microseconds. All timing constants had to be adapted and
microseconds. All timing constants had to be adapted and
can now be specified more precisely. They are automatically
can now be specified more precisely. They are automatically
scaled to clock cycles (see above).
scaled to clock cycles (see above).
e) The addressing scheme for peripherals of the same sort
e) The addressing scheme for peripherals of the same sort
has changed slightly. Virtual addresses of I/O devices have
has changed slightly. Virtual addresses of I/O devices have
the form 0xFxxyyrrr, where xx is the device type, yy is the
the form 0xFxxyyrrr, where xx is the device type, yy is the
device number, and rrr is the register within the device
device number, and rrr is the register within the device
(must be a word address). This change could affect existent
(must be a word address). This change could affect existent
programs which use more than one terminal.
programs which use more than one terminal.
f) The ECO32 simulation got a new peripheral, called the
f) The ECO32 simulation got a new peripheral, called the
"shutdown device". A write to address 0xFF100000 results
"shutdown device". A write to address 0xFF100000 results
in terminating the simulation run, with the lower 8 bits
in terminating the simulation run, with the lower 8 bits
of the data written supplied as exit status.
of the data written supplied as exit status.
19-Feb-2014
19-Feb-2014
In the hardware section, only the latest FPGA implementation
In the hardware section, only the latest FPGA implementation
was kept.
was kept.
20-Feb-2014
20-Feb-2014
New ISE project file created. In the LCC section, lburg/gram.c
New ISE project file created. In the LCC section, lburg/gram.c
gets re-generated from the grammar file. Two new simulator
gets re-generated from the grammar file. Two new simulator
tests written. Standalone programs updated.
tests written. Standalone programs updated.
22-Feb-2014
22-Feb-2014
Tools: bin2exo tool updated, bin2mcs tool added. Hardware:
Tools: bin2exo tool updated, bin2mcs tool added. Hardware:
character generator generator added, display memory generator
character generator generator added, display memory generator
added. Monitor: load server added. Disk: disk server renamed
added. Monitor: load server added. Disk: disk server renamed
and updated.
and updated.
23-Feb-2014
23-Feb-2014
Monitor directories re-structured. Monitors extensively updated.
Monitor directories re-structured. Monitors extensively updated.
FPGA implementation updated; timer is now equal to port-15.
FPGA implementation updated; timer is now equal to port-15.
24-Feb-2014
24-Feb-2014
Hardware: timer counts clock cycles, counter is readable, two
Hardware: timer counts clock cycles, counter is readable, two
timers are now available.
timers are now available.
25-Feb-2014
25-Feb-2014
Simulator: IRQ 15 explanation added, IRQ 0-3 explanations
Simulator: IRQ 15 explanation added, IRQ 0-3 explanations
changed.
changed.
26-Feb-2014
26-Feb-2014
Hardware: cpu is now equal to port-15. Constraints file for
Hardware: cpu is now equal to port-15. Constraints file for
XESS board re-formatted.
XESS board re-formatted.
27-Feb-2014
27-Feb-2014
Simulator: tlbBadAddr register is now called mmuBadAddr.
Simulator: tlbBadAddr register is now called mmuBadAddr.
28-Feb-2014
28-Feb-2014
Hardware tests (kbdtest): second timer added.
Hardware tests (kbdtest): second timer added.
01-Mar-2014
01-Mar-2014
Hardware tests (xcptest): test the bad address register too.
Hardware tests (xcptest): test the bad address register too.
Hardware: cpu now also has a bad address register.
Hardware: cpu now also has a bad address register.
*****************************************************************
*****************************************************************
Stefan Kristiansson's Linux port to ECO32 is running on the FPGA!
Stefan Kristiansson's Linux port to ECO32 is running on the FPGA!
*****************************************************************
*****************************************************************
Simulator: change command @ -> #, better help for commands.
Simulator: change command @ -> #, better help for commands.
Simulator: individual help messages corrected.
Simulator: individual help messages corrected.
02-Mar-2014
02-Mar-2014
Monitor: bad address register added.
Monitor: bad address register added.
Monitor: bootstrap parameters modified.
Monitor: bootstrap parameters modified.
Disk: master boot made compatible with monitor.
Disk: master boot made compatible with monitor.
03-Mar-2014
03-Mar-2014
DE0-Nano board arrived. I can download a simple design.
DE0-Nano board arrived. I can download a simple design.
04-Mar-2014
04-Mar-2014
The Nano board does only have a bit-serial ROM. Besides the
The Nano board does only have a bit-serial ROM. Besides the
configuration bitstring for the FPGA there is enough room in
configuration bitstring for the FPGA there is enough room in
it to store the machine monitor, but this program cannot
it to store the machine monitor, but this program cannot
reasonably be executed from there. So it must be copied to
reasonably be executed from there. So it must be copied to
RAM before it can be started. This is also the case with the
RAM before it can be started. This is also the case with the
S3E starter kit board - this board indeed does have a parallel
S3E starter kit board - this board indeed does have a parallel
ROM but alas, it must be disabled in order to use the A/D or
ROM but alas, it must be disabled in order to use the A/D or
D/A converters. Therefore it is best to run the monitor from
D/A converters. Therefore it is best to run the monitor from
RAM in any case. Consequences: the boot procedures must again
RAM in any case. Consequences: the boot procedures must again
be revised.
be revised.
Monitor: do not set sp on bootstrap.
Monitor: do not set sp on bootstrap.
EOS32 bootstrap update.
EOS32 bootstrap update.
05-Mar-2014
05-Mar-2014
Simulator: -a command line option added (which specifies a load
Simulator: -a command line option added (which specifies a load
address where a binary file is loaded when -l  is given).
address where a binary file is loaded when -l  is given).
Compiler: -Wo-kernel relocates code to 0xC0010000.
Compiler: -Wo-kernel relocates code to 0xC0010000.
06-Mar-2014
06-Mar-2014
Standalone programs (hello, hello2, memsize, onetask, twotasks-1,
Standalone programs (hello, hello2, memsize, onetask, twotasks-1,
twotasks-2) executable at 0xC0010000.
twotasks-2) executable at 0xC0010000.
07-Mar-2014
07-Mar-2014
Standalone programs (wrtmbr, dskchk) executable at 0xC0010000.
Standalone programs (wrtmbr, dskchk) executable at 0xC0010000.
08-Mar-2014
08-Mar-2014
Standalone programs (shpart, mkpart) executable at 0xC0010000.
Standalone programs (shpart, mkpart) executable at 0xC0010000.
Verified the four ways that a standalone program can be executed:
Verified the four ways that a standalone program can be executed:
  - simulator and -l/-a command line options
  - simulator and -l/-a command line options
  - simulator and simulated disk (boot the standalone program)
  - simulator and simulated disk (boot the standalone program)
  - FPGA and load server (load the standalone program)
  - FPGA and load server (load the standalone program)
  - FPGA and simulated disk (boot the standalone program)
  - FPGA and simulated disk (boot the standalone program)
09-Mar-2014
09-Mar-2014
NetBSD bootstrap now executing at 0xC0010000.
NetBSD bootstrap now executing at 0xC0010000.
14-Mar-2014
14-Mar-2014
Hardware: kbd is now equal to port-15.
Hardware: kbd is now equal to port-15.
Hardware: ser is now equal to port-15.
Hardware: ser is now equal to port-15.
15-Mar-2014
15-Mar-2014
Hardware: rom is now equivalent to port-15.
Hardware: rom is now equivalent to port-15.
Hardware: ram is now equivalent to port-15.
Hardware: ram is now equivalent to port-15.
16-Mar-2014
16-Mar-2014
Hardware: in cpu/sregs change signal names di->din, do->dout
Hardware: in cpu/sregs change signal names di->din, do->dout
(simulation tool 'Verilator' doesn't like 'do' as signal name).
(simulation tool 'Verilator' doesn't like 'do' as signal name).
Hardware: dsk source formatted.
Hardware: dsk source formatted.
Hardware: in sdramcntl.v signal added to sensitivity list.
Hardware: in sdramcntl.v signal added to sensitivity list.
Hardware: dsp is now equivalent to port-15.
Hardware: dsp is now equivalent to port-15.
17-Mar-2014
17-Mar-2014
Hardware: busctrl source formatted.
Hardware: busctrl source formatted.
Hardware: cpu external pin ordering changed.
Hardware: cpu external pin ordering changed.
Hardware: ram pin ordering changed.
Hardware: ram pin ordering changed.
Hardware: clock/reset source formatted.
Hardware: clock/reset source formatted.
18-Mar-2014
18-Mar-2014
Hardware: clock/reset update.
Hardware: clock/reset update.
 
 
 
30-Mar-2014
 
Hardware tests: serial/fpga2pc verified, README added.
 
Hardware tests: serial/pc2fpga verified, README added.
 
 
 
31-Mar-2014
 
Hardware tests: serial/sertest verified, README added.
 
Hardware tests: looptest verified, README added.
 
Hardware tests: ldtest verified, README added.
 
Hardware tests: memtest1 verified, README added.
 
Hardware tests: memtest2 verified, README added.
 
Hardware tests: shtest verified, README added.
 
Hardware tests: serial README added.
 
Hardware tests: brtest verified, README added.
 
Hardware tests: tmrtest verified, README added.
 
Hardware tests: multest verified, README added.
 
Hardware tests: divtest verified, README added.
 
 
 
01-Apr-2014
 
Hardware tests: remtest verified, README added.
 
Hardware tests: sregtest verified, README added.
 
Hardware tests: tlbtest verified, README added.
 
Hardware tests: irqtest verified, README added.
 
Hardware tests: xcptest verified, README added.
 
Hardware tests: dsptest verified, README added.
 
 
 
02-Apr-2014
 
Hardware tests: kbdtest verified, README added.
 
Hardware tests: jalrtest verified, README added.
 
Release eco32-0.23 tagged.
 
 

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