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#
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# $Id: README,v 1.2 2001-09-27 11:59:29 chris Exp $
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#
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There are various issues regarding this port:
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1) Legal
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This port is written by Andrew Bray , and
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is copyright 1995 i-cubed ltd.
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This port was later updated by Joel Sherrill
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to test the support for the PPC603, PPC603e, and MPC604. This
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was tested on the PowerPC simulator PSIM and a VMEbus single board
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computer.
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2) CPU support.
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This release fully supports the PPC403GA, PPC403GB, PPC603, PPC603e,
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MPC604, MPC750, and numerous MPC8xx processors. A good faith attempt
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has been made to include support other models based upon available
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documentation including the MPC5xx. There are two interrupt structures
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supported by the PowerPC port. The newer structure is supported by
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all the MPC750 and MPC604 BSPs. This structure is required to use
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the RDBG remote debugging support.
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This port was originally written and tested on the PPC403GA (using
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software floating point). Current ports are tested primarily on
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60x CPUs using the PowerPC simulator PSIM.
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Andrew Bray received assistance during the initial porting effort
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from IBM and Blue Micro and we would like to gratefully acknowledge
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that help.
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The support for the PPC602 processor is incomplete as only sketchy
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data is currently available. Perhaps this model has been dropped.
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3) Application Binary Interface
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In the context of RTEMS, the ABI is of interest for the following
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aspects:
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a) Register usage. Which registers are used to provide static variable
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linkage, stack pointer etc.
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b) Function calling convention. How parameters are passed, how function
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variables should be invoked, how values are returned, etc.
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c) Stack frame layout.
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I am aware of a number of ABIs for the PowerPC:
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a) The PowerOpen ABI. This is the original Power ABI used on the RS/6000.
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This is the only ABI supported by versions of GCC before 2.7.0.
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b) The SVR4 ABI. This is the ABI defined by SunSoft for the Solaris port
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to the PowerPC.
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c) The Embedded ABI. This is an embedded ABI for PowerPC use, which has no
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operating system interface defined. It is promoted by SunSoft, Motorola,
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and Cygnus Support. Cygnus are porting the GNU toolchain to this ABI.
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d) GCC 2.7.0. This compiler is partway along the road to supporting the EABI,
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but is currently halfway in between.
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This port was built and tested using the PowerOpen ABI, with the following
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caveat: we used an ELF assembler and linker. So some attention may be
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required on the assembler files to get them through a traditional (XCOFF)
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PowerOpen assembler.
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This port contains support for the other ABIs, but this may prove to be
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incomplete as it is untested.
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The RTEMS PowerPC port supports EABI as the primary ABI. The powerpc-rtems
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GNU toolset configuration is EABI.
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Andrew Bray, 4 December 1995
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Joel Sherrill, 16 July 1997
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