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                PSIM 1.0.1 - Model of the PowerPC Environments

    Copyright (C) 1994-1996, Andrew Cagney .

    This program is free software; you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by

    the Free Software Foundation; either version 2 of the License, or

    (at your option) any later version.

    This program is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of

    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License

    along with this program; if not, write to the Free Software

    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

    ----------------------------------------------------------------------

PSIM is a program written in extended ANSI-C that implements an

instruction level simulation of the PowerPC environment.  It is freely

available in source code form under the terms of the GNU General

Public License (version 2 or later).

The PowerPC Architecture is described as having three levels of

compliance:

        UEA - User Environment Architecture

        VEA - Virtual Environment Architecture

        OEA - Operating Environment Architecture

PSIM both implements all three levels of the PowerPC and includes (for

each level) a corresponding simulated run-time environment.

In addition, PSIM, to the execution unit level, models the performance

of most of the current PowerPC implementations (contributed by Michael

Meissner).  This detailed performance monitoring (unlike many other

simulators) resulting in only a relatively marginal reduction in the

simulators performance.

A description of how to build PSIM is contained in the file:

                ftp://ftp.ci.com.au/pub/psim/INSTALL

        or      ftp://cambridge.cygnus.com/pub/psim/INSTALL

while an overview of how to use PSIM is in:

        ftp://ftp.ci.com.au/pub/psim/RUN

or      ftp://cambridge.cygnus.com/pub/psim/RUN

This file is found in:

        ftp://ftp.ci.com.au/pub/psim/README

or      ftp://cambridge.cygnus.com/pub/psim/README

Thanks goes firstly to:

        Corinthian Engineering Pty Ltd

        Cygnus Support

        Highland Logic Pty Ltd

who provided the resources needed for making this software available

on the Internet.

More importantly I'd like to thank the following individuals who each

contributed in their own unique way:

        Allen Briggs, Bett Koch, David Edelsohn, Gordon Irlam,

        Michael Meissner, Bob Mercier, Richard Perini, Dale Rahn,

        Richard Stallman, Mitchele Walker

                                Andrew Cagney

                                Feb, 1995

    ----------------------------------------------------------------------

    What features does PSIM include?

        Monitoring and modeling

                PSIM includes (thanks to Michael Meissner)

                a detailed model of most of the PowerPC

                implementations to the functional unit level.

        SMP

                The PowerPC ISA defines SMP synchronizing instructions.

                This simulator implements a limited, but functional,

                subset of the PowerPC synchronization instructions

                behaviour.  Programs that restrict their synchronization

                primitives to those that work with this functional

                sub-set (eg P() and V()) are able to run on the SMP

                version of PSIM.

                People intending to use this system should study

                the code implementing the lwarx instruction.

        ENDIAN SUPPORT

                PSIM implements the PowerPC's big and little (xor

                endian) modes and correctly simulates code that

                switches between these two modes.

                In addition, psim can model a true little-endian

                machine.

        ISA (Instruction Set Architecture) models

                PSIM includes a model of the UEA, VEA and OEA.  This

                includes the time base registers (VEA) and HTAB

                and BATS (OEA).

                In addition, a preliminary model of the 64 bit

                PowerPC architecture is implemented.

        IO Hardware

                PSIM's internals are based around the concept

                of a Device Tree.  This tree intentionally

                resembles that of the Device Tree found in

                OpenBoot firmware.  PSIM is flexible enough

                to allow the user to fully configure this device

                tree (and consequently the hardware model) at

                run time.

        Run-time environments:

                PSIM's UEA model includes emulation for BSD

                based UNIX system calls.

                PSIM's OEA model includes emulation of either:

                        o       OpenBoot client interface

                        o       MOTO's BUG interface.

        Floating point

                Preliminary support for floating point is included.

    Who would be interested in PSIM?

        o       the curious

                Using psim, gdb, gcc and binutils the curious

                user can construct an environment that allows

                them to play with PowerPC Environment without

                the need for real hardware.

        o       the analyst

                PSIM includes many (contributed) monitoring

                features which (unlike many other simulators)

                do not come with a great penalty in performance.

                Thus the performance analyst is able to use

                this simulator to analyse the performance of

                the system under test.

                If PSIM doesn't monitor a components of interest,

                the source code is freely available, and hence

                there is no hinderance to changing things

                to meet a specific analysts needs.

        o       the serious SW developer

                PSIM models all three levels of the PowerPC

                Architecture: UEA, VEA and OEA.  Further,

                the internal design is such that PSIM can

                be extended to support additional requirements.

    What performance analysis measurements can PSIM perform?

        Below is the output from a recent analysis run

        (contributed by Michael Meissner):

        For the following program:

        long

        simple_rand ()

        {

          static unsigned long seed = 47114711;

          unsigned long this = seed * 1103515245 + 12345;

          seed = this;

        /* cut-cut-cut - see the file RUN.psim */

        }

        Here is the current output generated with the -I switch on a P90

        (the compiler used is the development version of GCC with a new

        scheduler replacing the old one):

        CPU #1 executed     41,994 AND instructions.

        CPU #1 executed    519,785 AND Immediate instructions.

        .

        .

        .

        CPU #1 executed          1 System Call instruction.

        CPU #1 executed    207,746 XOR instructions.

        CPU #1 executed 23,740,856 cycles.

        CPU #1 executed 10,242,780 stalls waiting for data.

        CPU #1 executed          1 stall waiting for a function unit.

        .

        .

        .

        CPU #1 executed  3,136,229 branch functional unit instructions.

        CPU #1 executed 16,949,396 instructions that were accounted for in timing info.

        CPU #1 executed    871,920 data reads.

        CPU #1 executed    971,926 data writes.

        CPU #1 executed        221 icache misses.

        CPU #1 executed 16,949,396 instructions in total.

        Simulator speed was 250,731 instructions/second

    What motivated PSIM?

        As an idea, psim was first discussed seriously during mid

        1994.  At that time its main objectives were:

                o       good performance

                        Many simulators loose out by only providing

                        a binary interface to the internals.  This

                        interface eventually becomes a bottle neck

                        in the simulators performance.

                        It was intended that PSIM would avoid this

                        problem by giving the user access to the

                        full source code.

                        Further, by exploiting the power of modern

                        compilers it was hoped that PSIM would achieve

                        good performance with out having to compromise

                        its internal design.

                o       practical portability

                        Rather than try to be portable to every

                        C compiler on every platform, it was decided

                        that PSIM would restrict its self to supporting

                        ANSI compilers that included the extension

                        of a long long type.

                        GCC is one such compiler, consequently PSIM

                        should be portable to any machine running GCC.

                o       flexibility in its design

                        PSIM should allow the user to select the

                        features required and customise the build

                        accordingly.  By having the source code,

                        the compiler is able to eliminate any un

                        used features of the simulator.

                        After all, let the compiler do the work.

                o       SMP

                        A model that allowed the simulation of

                        SMP platforms with out the large overhead

                        often encountered with such models.

        PSIM achieves each of these objectives.

    Is PSIM PowerPC Platform (PPCP) (nee CHRP) Compliant?

        No.

        Among other things it does not have an Apple ROM socket.

    Could PSIM be extended so that it models a CHRP machine?

        Yes.

        PSIM has been designed with the CHRP spec in mind. To model

        a CHRP desktop the following would need to be added:

                o       An apple ROM socket :-)

                o       Model of each of the desktop IO devices

                o       An OpenPIC device.

                o       RTAS (Run Time Abstraction Services).

                o       A fully populated device tree.

    Is the source code available?

        Yes.

        The source code to PSIM is available under the terms of

        the GNU Public Licence.  This allows you to distribute

        the source code for free but with certain conditions.

        See the file:

                ftp://archie.au/gnu/COPYING

        For details of the terms and conditions.

    Where do I send bugs or report problems?

        There is a mailing list (subscribe through majordomo@ci.com.au) at:

        powerpc-psim@ci.com.au

        If I get the ftp archive updated I post a note to that mailing list.

        In addition your welcome to send bugs or problems either to me or to

        that e-mail list.

        This list currently averages zero articles a day.

     Does PSIM have any limitations or problems?

        PSIM can't run rs6000/AIX binaries - At present PSIM can only

        simulate static executables.  Since an AIX executable is

        never static, PSIM is unable to simulate its execution.

        PSIM is still under development - consequently there are going

        to be bugs.

        See the file BUGS (included in the distribution) for any

        other outstanding issues.