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-revision 4 by dpavlin,
Mon Oct  8 16:18:00 2007 UTC
+revision 22 by dpavlin,
Mon Oct  8 16:19:37 2007 UTC
 Line 1
- <html>
+ <html><head><title>Gavare's eXperimental Emulator:&nbsp;&nbsp;&nbsp;Introduction</title>
- <head><title>GXemul documentation: Introduction</title>
+ <meta name="robots" content="noarchive,nofollow,noindex"></head>
- </head>
  <body bgcolor="#f8f8f8" text="#000000" link="#4040f0" vlink="#404040" alink="#ff0000">
  <table border=0 width=100% bgcolor="#d0d0d0"><tr>
  <td width=100% align=center valign=center><table border=0 width=100%><tr>
  <td align="left" valign=center bgcolor="#d0efff"><font color="#6060e0" size="6">
- <b>GXemul documentation:</b></font>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+ <b>Gavare's eXperimental Emulator:</b></font><br>
  <font color="#000000" size="6"><b>Introduction</b>
  </font></td></tr></table></td></tr></table><p>
- <!-- The first 10 lines are cut away by the homepage updating script.  -->
  <!--
- $Id: intro.html,v 1.40 2005/04/27 15:22:17 debug Exp $
+ $Id: intro.html,v 1.73 2006/02/18 14:02:19 debug Exp $
- Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.
+ Copyright (C) 2003-2006  Anders Gavare.  All rights reserved.
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:
-Line 48 
 SUCH DAMAGE.
+Line 45 
 SUCH DAMAGE.
  <h2>Introduction</h2>
  <p>
+ <table border="0" width="99%"><tr><td valign="top" align="left">
  <ul>
    <li><a href="#overview">Overview</a>
    <li><a href="#free">Is GXemul Free software?</a>
    <li><a href="#build">How to compile/build the emulator</a>
-   <li><a href="#cpus">Which CPU types does GXemul emulate?</a>
+   <li><a href="#run">How to run the emulator</a>
+   <li><a href="#cpus">Which processor architectures does GXemul emulate?</a>
    <li><a href="#accuracy">Emulation accuracy</a>
    <li><a href="#emulmodes">Which machines does GXemul emulate?</a>
-   <li><a href="#guestos">Which guest OSes are possible to run?</a>
  </ul>
+ </td><td valign="center" align="center">
+ <a href="20050317-example.png"><img src="20050317-example_small.png"></a>
+ <p>NetBSD/pmax 1.6.2 with X11<br>running in GXemul</td></tr></table>
 Line 66 
 SUCH DAMAGE.
  <a name="overview"></a>
  <h3>Overview:</h3>
- GXemul is a machine emulator, which can be used to experiment with
+ GXemul is an experimental instruction-level machine emulator. Several
- binary code for (among others) MIPS-based machines. Several emulation
+ emulation modes are available. In some modes, processors and surrounding
- modes are available. For some emulation modes, processors and surrounding
  hardware components are emulated well enough to let unmodified operating
- systems run as if they were running on a real machine.
+ systems (e.g. NetBSD) run as if they were running on a real machine.
- <p>
+ <p>The processor architecture best emulated by GXemul is MIPS, but other
- It is important to keep in mind that devices and CPUs are not simulated
+ architectures such as ARM and PowerPC are also partially emulated.
- with 100% accuracy. They are only "faked" well enough to make operating
- systems (eg NetBSD) run. Still, the emulator could be of interest for
+ <p>Devices and CPUs are not simulated with 100% accuracy. They are only
- academic research and experiments, such as when learning how to write
+ ``faked'' well enough to allow guest operating systems run without
+ complaining too much. Still, the emulator could be of interest for
+ academic research and experiments, such as when learning how to write
  operating system code.
- <p>
+ <p>The emulator is written in C, does not depend on third-party libraries,
- The emulator is written in C, does not depend on external libraries (except
+ and should compile and run on most 64-bit and 32-bit Unix-like systems.
- X11, but that is optional), and should compile and run on most Unix-like
- systems. If it doesn't, then that is a bug.
- (You do not need any MIPS compiler toolchain to build or use GXemul.
- If you need to compile MIPS binaries from sources, then of course you need
- such a toolchain, but that is completely separate from GXemul. There
- is a <a href="technical.html#regtest">regression testing</a> framework,
- which requires that a GNU CC for mips64-unknown-elf or similar is available.
- For simply building and using the emulator, it is not required.)
- <p>
+ <p>The emulator contains code which tries to emulate the workings of CPUs
- The emulator contains code which tries to emulate the workings of CPUs and
+ and surrounding hardware found in real machines, but it does not contain
- surrounding hardware found in real machines, but it does not contain any
+ any ROM code. You will need some form of program (in binary form) to run
- ROM code. You will need some form of program (in binary form) to run in
+ in the emulator. For many emulation modes, PROM calls are handled by the
- the emulator. For many emulation modes, PROM calls are handled by the
  emulator itself, so you do not need to use any ROM image at all.
- <p>
+ <p>You can use pre-compiled kernels (for example NetBSD kernels, or
- You can use pre-compiled kernels (for example NetBSD kernels, or Linux),
+ Linux), or other programs that are in binary format, and in some cases
- or other programs that are in binary format, and in some cases even actual
+ even actual ROM images. A couple of different file formats are supported
- ROM images. A couple of different file formats are supported (ELF, a.out,
+ (ELF, a.out, ECOFF, SREC, and raw binaries).
- ECOFF, SREC, raw binaries).
+ <p>If you do not have a kernel as a separate file, but you have a bootable
+ disk image, then it is sometimes possible to boot directly from that
+ image. (This works for example with DECstation emulation, or when booting
+ from ISO9660 CDROM images.)
- <p><br>
- <a name="free"></a>
- <h3>Is GXemul Free software?</h3>
- Yes. I have released GXemul under a Free license.
- (For a definitions of the four freedoms associated with Free software,
- please read <a href="http://www.gnu.org/philosophy/free-sw.html">
- http://www.gnu.org/philosophy/free-sw.html</a>.)
- <p>
- The code in GXemul is Copyrighted software, it is <i>not</i> public
- domain or anything like that.
- <p>
+ <p><br>
- The code I have written is released under a 3-clause BSD-style license
+ <a name="free"></a>
- (or "revised BSD-style" if one wants to use
+ <h3>Is GXemul Free software?</h3>
- <a href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>).
- Apart from the code I have written, some files are copied from other sources
- such as NetBSD, for example header files containing symbolic names of
- bitfields in device registers. They are also covered by similar licenses,
- but with some additional clauses. If you plan to redistribute GXemul
- (for example as a binary package), or reuse code from GXemul,
- then you should check those files for their license terms.
- <p>
+ Yes. I have released GXemul under a Free license. The code in GXemul is
- (The licenses usually require that the original Copyright and license
+ Copyrighted software, it is <i>not</i> public domain. (If this is
- terms are included when you make a copy or modification. The "easiest way
+ confusing to you, you might want to read up on the definitions of the
- out" if you plan to redistribute code from GXemul is to simply supply
+ four freedoms associated with Free software, <a
- the source code. You should however check individual files for details.)
+ href="http://www.gnu.org/philosophy/free-sw.html">http://www.gnu.org/philosophy/free-sw.html</a>.)
+ <p>The code I have written is released under a 3-clause BSD-style license
+ (or "revised BSD-style" if one wants to use <a
+ href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>). Apart from
+ the code I have written, some files are copied from other sources such as
+ NetBSD, for example header files containing symbolic names of bitfields in
+ device registers. They are also covered by similar licenses, but with some
+ additional clauses. The main point, however, is that the licenses require
+ that the original Copyright and license terms are included when you make a
+ copy or modification.
+ <p>If you plan to redistribute GXemul <i>without</i> supplying the source
+ code, then you need to comply with each individual source file some other
+ way, for example by writing additional documentation containing copyright
+ notes. I have not done this, since I do not plan on making distributions
+ without source code. You need to check all individual files for details.
+ The "easiest way out" if you plan to redistribute code from GXemul is, of
+ course, to let it remain open source and simply supply the source code.
+ <p>In case you want to reuse parts of GXemul, but you need to do that
+ under a different license (e.g. the GPL), then contact me and I might
+ re-license/dual-license files on a case-by-case basis.
-Line 151 
 Uncompress the .tar.gz distribution file
+Line 152 
 Uncompress the .tar.gz distribution file
          $ <b>make</b>
  </pre>
- <p>
+ <p>This should work on most Unix-like systems. GXemul does not require any
- This should work on most Unix-like systems. If it doesn't, then
+ specific libraries to build, however, if you build on a system which does
- mail me a bug report.
+ not have X11 libraries installed, some functionality will be lost.
- <p>
- (Note for Windows users: there is a possibility that some releases
- and/or snapshots will also work with Cygwin, but I can't promise that.)
- <p>
+ <p>The emulator's performance is highly dependent on both runtime settings
- The emulator's performance is highly dependent on both runtime settings
  and on compiler settings, so you might want to experiment with different
- CC and CFLAGS environment variable values. For example, on a modern PC,
+ CC and CFLAGS environment variable values. For example, on an AMD Athlon
- you could try the following:
+ host, you might want to try setting <tt>CFLAGS</tt> to <tt>-march=athlon
- <p>
+ -O3</tt> before running <tt>configure</tt>.
- <pre>
-         $ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b>
-         $ <b>make</b>
- </pre>
+ <p><br>
+ <a name="run"></a>
+ <h3>How to run the emulator:</h3>
+ Once you have built GXemul, running it should be rather straight-forward.
+ Running <tt><b>gxemul</b></tt> without arguments (or with the
+ <b><tt>-h</tt></b> or <b><tt>-H</tt></b> command line options) will
+ display a help message.
  <p>
- Run <b>./configure --help</b> to get a list of configure options. (The
+ To get some ideas about what is possible to run in the emulator, please
- possible options differ between different releases and snapshots.)
+ read the section about <a href="guestoses.html">installing "guest"
+ operating systems</a>. If you are interested in using the emulator to
+ develop code on your own, then you should also read the section about
+ <a href="experiments.html#hello">Hello World</a>.
  <p>
- Once you have built GXemul, running it should be rather straight-forward.
  To exit the emulator, type CTRL-C to enter the
- single-step debugger, and then type <b>quit</b>.
+ single-step debugger, and then type <tt><b>quit</b></tt>.
  <p>
  If you are starting an emulation by entering settings directly on the
- command line, and you are not using the <b>-x</b> option, then all
+ command line, and you are not using the <tt><b>-x</b></tt> option, then all
  terminal input and output will go to the main controlling terminal.
  CTRL-C is used to break into the debugger, so in order to send CTRL-C to
  the running (emulated) program, you may use CTRL-B.
+ (This should be a reasonable compromise to allow the emulator to be usable
+ even on systems without X Windows.)
  <p>
- (This is an ugly hack; there is no way to send an actual CTRL-B to the
+ There is no way to send an actual CTRL-B to the emulated program, when
- emulated program, when typing in the main controlling terminal window.
+ typing in the main controlling terminal window. The solution is to either
- The solution is to either use configuration files, or use <b>-x</b>. Both
+ use <a href="configfiles.html">configuration files</a>, or use
- these solutions cause new xterms to be opened for each emulated serial
+ <tt><b>-x</b></tt>. Both these solutions cause new xterms to be opened for
- port. CTRL-B and CTRL-C both have their original meaning in those
+ each emulated serial port that is written to. CTRL-B and CTRL-C both have
- xterm windows.)
+ their original meaning in those xterm windows.
-Line 201 
 xterm windows.)
+Line 211 
 xterm windows.)
  <p><br>
  <a name="cpus"></a>
- <h3>Which CPU types does GXemul emulate?</h3>
+ <h3>Which processor architectures does GXemul emulate?</h3>
  <h4>MIPS:</h4>
- Emulation of R4000, which is a 64-bit CPU, was my initial goal. Right
+ Emulation of R4000, which is a 64-bit CPU, was my initial goal.
- now, R2000/R3000-like CPUs are also emulated (32-bit), and emulation of
+ R2000/R3000-like CPUs (32-bit), R1x000, and generic MIPS32/MIPS64-style
- R1x000 (at least the parts that are similar to R4000) is beginning to work
+ CPUs are also emulated, and are hopefully almost as stable as the R4000
- as expected. Code targeted for MIPS32 and MIPS64 also often work.
+ emulation. Several guest operating systems for MIPS can run inside
+ the emulator.
- <p>
- I have written an experimental dynamic binary translation subsystem.
+ <p>(For MIPS emulation, I have written an experimental dynamic binary
- This gives higher total performance than interpreting one instruction at a
+ translation subsystem, for Alpha and i386 hosts. This gives higher total
- time and executing it. (If you wish to enable bintrans, add <b>-b</b> to
+ performance than interpreting one instruction at a time and executing it.
- the command line, but keep in mind that it is still experimental.)
+ If you wish to disable bintrans, add <b>-B</b> to the command line.)
+ <h4>ARM:</h4>
+ ARM emulation is good enough to run NetBSD/cats, OpenBSD/cats, and
+ NetBSD/evbarm, but it is not as tested or fine-tuned as the MIPS emulation
+ mode.
- <h4>URISC:</h4>
+ <h4>PowerPC:</h4>
- I have implemented an <a href="http://en.wikipedia.org/wiki/URISC">URISC</a>
+ PowerPC emulation is still in its beginning stages, but good enough
- emulation mode, just for fun. The only instruction available in an URISC
+ to run NetBSD/prep 2.1.
- machine is "reverse subtract and skip on borrow". (It is probably not
- worth trying to do bintrans with URISC, because any reasonable URISC
- program relies on self-modifying code, which is bad for bintrans
- performance.)
+ <p>Non-MIPS emulation modes use dynamic translation, but not recompilation
+ into native code. This makes it possible to run on any host platform.
- <h4>Other CPU types:</h4>
- There is some code for 64-bit (and 32-bit) POWER/PowerPC emulation too,
- but it only works for "Hello World" and similarly trivial programs. (There
- are some other CPU modes too, but they are working even less.)
-Line 244 
 are some other CPU modes too, but they a
+Line 248 
 are some other CPU modes too, but they a
  <a name="accuracy"></a>
  <h3>Emulation accuracy:</h3>
- GXemul is an instruction-level simulator; things that would happen in
+ GXemul is an instruction-level emulator; things that would happen in
  several steps within a real CPU are not taken into account (eg. pipe-line
- stages or out-of-order execution). Still, instruction-level accuracy seems
+ stalls or out-of-order execution). Still, instruction-level accuracy seems
  to be enough to be able to run complete guest operating systems inside the
  emulator.
+ <p>Caches are by default not emulated. In some cases, the existance of
+ caches is "faked" to let operating systems think that they are there.
+ (There is some old code for R2000/R3000 caches, but it has probably
+ suffered from bitrot by now.)
+ <p>The emulator is <i>not</i> timing-accurate. It can be run in a
+ "deterministic" mode, <tt><b>-D</b></tt>. The meaning of deterministic is
+ simply that running two emulations with the same settings will result in
+ identical runs. Obviously, this requires that no user interaction is
+ taking place, and that clock speeds are fixed with the <tt><b>-I</b></tt>
+ option. (Deterministic in this case does <i>not</i> mean that the
+ emulation will be identical to some actual real-world machine.)
+ <p><font color="#ff0000">(Oops/TODO: User interaction means <i>both</i>
+ input to the emulated program/OS, and interacting with the emulator
+ itself. Breaking into the debugger and then continuing execution may
+ affect when/how interrupts occur.)</font>
-Line 263 
 are emulated well enough to run at least
+Line 286 
 are emulated well enough to run at least
  <p>
  <ul>
-   <li><b>DECstation 5000/200</b>&nbsp;&nbsp;("3max")
+   <li><b><u>MIPS</u></b>
-         <br>Serial controller (including keyboard and mouse), ethernet,
+   <ul>
-         SCSI, and graphical framebuffers.
+     <li><b>DECstation 5000/200</b>&nbsp;&nbsp;("3max")
+     <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)
+     <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)
+     <li><b>Cobalt</b>
+     <li><b>Malta</b> (evbmips)
+     <li><b>SGI O2 ("IP32")</b> <font color="#0000e0">(<super>*</super>)</font>
+   </ul>
    <p>
-   <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)
+   <li><b><u>ARM</u></b>
-         <br>Serial controller, "VGA" text console, and SCSI.
+   <ul>
+     <li><b>CATS</b>
+     <li><b>IQ80321</b> (evbarm)
+   </ul>
    <p>
-   <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)
+   <li><b><u>PowerPC</u></b>
-         <br>Framebuffer, keyboard, and a PCMCIA IDE controller.
+   <ul>
-   <p>
+     <li><b>PReP (PowerPC Reference Platform)</b>
-   <li><b>Cobalt</b>
+   </ul>
-         <br>Serial controller and PCI IDE.
  </ul>
- <p>
+ <p><small><font color="#0000e0">(<super>*</super>)</font> =
- There is code in GXemul for emulation of many other machine types;
+ Enough for root-on-nfs, but not for disk boot.)</small>
- the degree to which these work range from "almost" being able to run
- a complete OS, to almost completely unsupported (perhaps just enough
- support to output a few boot messages via serial console).
- <p>
+ <p>There is code in GXemul for emulation of many other machine types; the
- In addition to emulating real machines, there is also a "test-machine".
+ degree to which these work range from almost being able to run a complete
- A test-machine consists of one or more CPUs and a few experimental
+ OS, to almost completely unsupported (perhaps just enough support to
- devices such as:
+ output a few boot messages via serial console).
+ <p>In addition to emulating real machines, there is also a "test-machine".
+ A test-machine consists of one or more CPUs and a few experimental devices
+ such as:
  <p>
  <ul>
    <li>a console I/O device (putchar() and getchar()...)
    <li>an inter-processor communication device, for SMP experiments
    <li>a very simple linear framebuffer device (for graphics output)
+   <li>a simple SCSI disk controller
+   <li>a simple ethernet controller
  </ul>
- <p>
+ <p>This mode is useful if you wish to run experimental code, but do not
- This mode is useful if you wish to run experimental code, but do not
  wish to target any specific real-world machine type, for example for
  educational purposes.
- <p>
+ <p>You can read more about these experimental devices <a
- You can read more about these experimental devices
+ href="experiments.html#expdevices">here</a>.
- <a href="experiments.html#expdevices">here</a>.
- <p><br>
- <a name="guestos"></a>
- <h3>Which guest OSes are possible to run?</h3>
- This table lists the guest OSes that run well enough to be considered
- working in the emulator. They can boot from a harddisk image and be
- interacted with similar to a real machine.
- <p>
- <center><table border="0">
-         <tr>
-           <td width="10"></td>
-           <td align="center"><a href="netbsd-pmax-20040630.png"><img src="netbsd-pmax-20040630_small.png"></a></td>
-           <td width="15"></td>
-           <td><a href="http://www.netbsd.org/Ports/pmax/">NetBSD/pmax</a>
-                 <br>DECstation 5000/200</td>
-           <td width="30"></td>
-           <td align="center"><a href="20041024-netbsd-arc-installed.gif"><img src="20041024-netbsd-arc-installed_small.gif"></a></td>
-           <td width="15"></td>
-           <td><a href="http://www.netbsd.org/Ports/arc/">NetBSD/arc</a>
-                 <br>Acer Pica-61</td>
-         </tr>
-         <tr><td height="10"></td></tr>
-         <tr>
-           <td></td>
-           <td align="center"><a href="openbsd-pmax-20040710.png"><img src="openbsd-pmax-20040710_small.png"></a></td>
-           <td></td>
-           <td><a href="http://www.openbsd.org/pmax.html">OpenBSD/pmax</a>
-                 <br>DECstation 5000/200</td>
-           <td></td>
-           <td align="center"><a href="20041024-openbsd-arc-installed.gif"><img src="20041024-openbsd-arc-installed_small.gif"></a></td>
-           <td></td>
-           <td><a href="http://www.openbsd.org/arc.html">OpenBSD/arc</a>
-                 <br>Acer Pica-61</td>
-         </tr>
-         <tr><td height="10"></td></tr>
-         <tr>
-           <td></td>
-           <td align="center"><a href="ultrix4.5-20040706.png"><img src="ultrix4.5-20040706_small.gif"></a></td>
-           <td></td>
-           <td>Ultrix/RISC<br>DECstation 5000/200</td>
-           <td></td>
-           <td align="center"><a href="20041213-debian_4.png"><img src="20041213-debian_4_small.gif"></a></td>
-           <td></td>
-           <td><a href="http://www.debian.org/">Debian&nbsp;GNU/Linux</a>&nbsp;<super>*</super>
-                 <br>DECstation 5000/200</td>
-         </tr>
-         <tr><td height="10"></td></tr>
-         <tr>
-           <td></td>
-           <td align="center"><a href="sprite-20040711.png"><img src="sprite-20040711_small.png"></a></td>
-           <td></td>
-           <td><a href="http://www.cs.berkeley.edu/projects/sprite/retrospective.html">Sprite</a>
-                 <br>DECstation 5000/200</td>
-           <td></td>
-           <td align="center"><a href="20041129-redhat_mips.png"><img src="20041129-redhat_mips_small.png"></a></td>
-           <td></td>
-           <td>Redhat&nbsp;Linux&nbsp;<super>*</super>
-                 <br>DECstation 5000/200</td>
-         </tr>
-         <tr><td height="10"></td></tr>
-         <tr>
-           <td></td>
-           <td align="center"><a href="20050427-netbsd-hpcmips-2.png"><img src="20050427-netbsd-hpcmips-2_small.png"></a></td>
-           <td></td>
-           <td><a href="http://www.netbsd.org/Ports/hpcmips/">NetBSD/hpcmips</a>
-                 <br>NEC MobilePro 770, 780, 800, 880</td>
-           <td></td>
-           <td align="center"><a href="20050413-netbsd-cobalt.png"><img src="20050413-netbsd-cobalt_small.png"></a></td>
-           <td></td>
-           <td><a href="http://www.netbsd.org/Ports/cobalt/">NetBSD/cobalt</a>
-                 <br>Cobalt</td>
-         </tr>
- </table></center>
- <p><br>
- <super>*</super> Although Linux runs under DECstation emulation, the
- default 2.4.27 kernel in Debian GNU/Linux does not support keyboards on
- the 5000/200 (the specific DECstation model being emulated), so when the
- login prompt is reached you cannot interact with the system. Kaj-Michael
- Lang has compiled and made available a newer kernel from the current
- mips-linux development tree. You can find it here: <a
- href="http://home.tal.org/~milang/o2/kernels/">http://home.tal.org/~milang/o2/kernels</a>/<a
- href="http://home.tal.org/~milang/o2/kernels/vmlinux-2.4.29-rc2-r3k-mipsel-decstation">vmlinux-2.4.29-rc2-r3k-mipsel-decstation</a>
- This newer kernel supports keyboard input, but it does not have Debian's
- ethernet patches, so you will not be able to use keyboard/framebuffer
- <i>and</i> networking at the same time.
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