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-revision 8 by dpavlin,
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+revision 20 by dpavlin,
Mon Oct  8 16:19:23 2007 UTC
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- <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>
- <meta name="robots" content="noarchive,nofollow,noindex">
- </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:&nbsp;&nbsp;&nbsp;</b></font>
  <font color="#000000" size="6"><b>Introduction</b>
  </font></td></tr></table></td></tr></table><p>
  <!--
- $Id: intro.html,v 1.47 2005/06/04 22:47:49 debug Exp $
+ $Id: intro.html,v 1.66 2005/11/23 22:03:24 debug Exp $
  Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.
-Line 55 
 SUCH DAMAGE.
+Line 53 
 SUCH DAMAGE.
    <li><a href="#cpus">Which CPU types 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>
+   <li><a href="#guestos">Which guest OSes are possible to run in GXemul?</a>
  </ul>
-Line 66 
 SUCH DAMAGE.
+Line 64 
 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
- Devices and CPUs are not simulated with 100% accuracy. They are only
+ architectures such as ARM and PowerPC are also partially emulated.
- "faked" well enough to make operating systems (eg NetBSD) run without
+ <p>Devices and CPUs are not simulated with 100% accuracy. They are only
+ ``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
+ (except X11, but that is optional), and should compile and run on most
- X11, but that is optional), and should compile and run on most Unix-like
+ Unix-like systems.
- systems. If it doesn't, then that is a bug.
- (You do not need any MIPS compiler toolchain to build or use GXemul.
+ <p>The emulator contains code which tries to emulate the workings of CPUs
- If you need to compile MIPS binaries from sources, then of course you need
+ and surrounding hardware found in real machines, but it does not contain
- such a toolchain, but that is completely separate from GXemul.)
+ any ROM code. You will need some form of program (in binary form) to run
+ in the emulator. For many emulation modes, PROM calls are handled by the
- <p>
- The emulator contains code which tries to emulate the workings of CPUs and
- surrounding hardware found in real machines, but it does not contain any
- ROM code. You will need some form of program (in binary form) to run in
- 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, and raw binaries).
- <p>
+ <p>If you do not have a kernel as a separate file, but you have a bootable
- 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.)
-Line 111 
 from ISO9660 CDROM images.)
+Line 103 
 from ISO9660 CDROM images.)
  <p><br>
  <a name="free"></a>
  <h3>Is GXemul Free software?</h3>
-Line 121 
 confusing to you, you might want to read
+Line 115 
 confusing to you, you might want to read
  four freedoms associated with Free software, <a
  href="http://www.gnu.org/philosophy/free-sw.html">http://www.gnu.org/philosophy/free-sw.html</a>.)
- <p>
+ <p>The code I have written is released under a 3-clause BSD-style license
- The code I have written is released under a 3-clause BSD-style license
+ (or "revised BSD-style" if one wants to use <a
- (or "revised BSD-style" if one wants to use
+ href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>). Apart from
- <a href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>).
+ the code I have written, some files are copied from other sources such as
- Apart from the code I have written, some files are copied from other sources
+ NetBSD, for example header files containing symbolic names of bitfields in
- such as NetBSD, for example header files containing symbolic names of
+ device registers. They are also covered by similar licenses, but with some
- bitfields in device registers. They are also covered by similar licenses,
+ additional clauses. The main point, however, is that the licenses require
- but with some additional clauses. If you plan to redistribute GXemul
+ that the original Copyright and license terms are included when you make a
- (for example as a binary package), or reuse code from GXemul,
+ copy or modification.
- then you should check those files for their license terms.
+ <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>(If a stable, unmodified release of GXemul is packaged into binary form,
+ and it is clear which version of GXemul was used to build the package,
+ then it can be argued that the source code is available, just not in that
+ specific package. Common sense should be used in this case, and not
+ pedanticism.)
- <p>
- (The licenses usually require that the original Copyright and license
- terms are included when you make a copy or modification. The "easiest way
- out" if you plan to redistribute code from GXemul is to simply supply
- the source code. You should however check individual files for details.)
-Line 152 
 Uncompress the .tar.gz distribution file
+Line 154 
 Uncompress the .tar.gz distribution file
          $ <b>make</b>
  </pre>
- <p>
+ <p>This should work on most Unix-like systems. If it doesn't, then
- This should work on most Unix-like systems. If it doesn't, then
  mail me a bug report.
- <p>
+ <p>The emulator's performance is highly dependent on both runtime settings
- (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>
- 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>
- Run <b><tt>./configure --help</tt></b> to get a list of configure options. (The
- possible options differ between different releases and snapshots.)
-Line 230 
 their original meaning in those xterm wi
+Line 219 
 their original meaning in those xterm wi
  Emulation of R4000, which is a 64-bit CPU, was my initial goal.
  R2000/R3000-like CPUs (32-bit), R1x000, and generic MIPS32/MIPS64-style
  CPUs are also emulated, and are hopefully almost as stable as the R4000
- emulation.
+ emulation. Several guest operating systems for MIPS can run inside
+ the emulator.
- <p>
- I have written an experimental dynamic binary translation subsystem.
- This gives higher total performance than interpreting one instruction at a
- time and executing it. (If you wish to enable bintrans, add <b>-b</b> to
- the command line, but keep in mind that it is still experimental.)
- <h4>URISC:</h4>
- I have implemented an <a href="http://en.wikipedia.org/wiki/URISC">URISC</a>
+ <p>(For MIPS emulation, I have written an experimental dynamic binary
- emulation mode, just for fun. The only instruction available in an URISC
+ translation subsystem, for Alpha and i386 hosts. This gives higher total
- machine is "reverse subtract and skip on borrow". (It is probably not
+ performance than interpreting one instruction at a time and executing it.
- worth trying to do bintrans with URISC, because any reasonable URISC
+ If you wish to disable bintrans, add <b>-B</b> to the command line.)
- program relies on self-modifying code, which is bad for bintrans
- performance.)
+ <h4>ARM:</h4>
- <h4>POWER/PowerPC</h4>
+ ARM emulation is good enough to run NetBSD/cats 2.1 and OpenBSD/cats 3.8,
+ but it is not as tested or fine-tuned as the MIPS emulation mode.
- There is some code for 64-bit (and 32-bit) POWER/PowerPC emulation, enough
+ <h4>PowerPC:</h4>
- to run "Hello World", but not enough to run complete operating systems.
- This mode isn't really working yet.
+ PowerPC emulation is still in its beginning stages, but good enough
+ to run NetBSD/prep 2.1.
- <h4>Other CPU types:</h4>
+ <p>Non-MIPS emulation modes use dynamic translation, but not recompilation
+ into native code. This makes it possible to run on any host platform.
- Some other CPU architectures (such as x86) can also be partially emulated.
- These are not enabled by default though, because of their unstable-ness.
-Line 275 
 stalls or out-of-order execution). Still
+Line 254 
 stalls or out-of-order execution). Still
  to be enough to be able to run complete guest operating systems inside the
  emulator.
- <p>
+ <p>Caches are by default not emulated. In some cases, the existance of
- Caches are by default not emulated. In some cases, the existance of caches
+ caches is "faked" to let operating systems think that they are there.
- is "faked" to let operating systems think that they are there. (There is
+ (There is some old code for R2000/R3000 caches, but it has probably
- some old code for R2000/R3000 caches, but it has probably suffered from
+ suffered from bitrot by now.)
- 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>
- <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.)
-Line 303 
 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")
-   <p>
+     <p>
-   <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)
+     <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)
-         <br>Serial controller, "VGA" text console, and SCSI.
+     <p>
+     <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)
+     <p>
+     <li><b>Cobalt</b>
+     <p>
+     <li><b>Malta</b> (evbmips)
+     <p>
+     <li><b>SGI O2 ("IP32")</b>
+         <br><small>(Enough for root-on-nfs, but not for disk boot.)</small>
+   </ul>
    <p>
-   <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)
+   <li><b><u>ARM</u></b>
-         <br>Framebuffer, keyboard, and a PCMCIA IDE controller.
+   <ul>
+     <li><b>CATS</b>
+   </ul>
    <p>
-   <li><b>Cobalt</b>
+   <li><b><u>PowerPC</u></b>
-         <br>Serial controller and PCI IDE.
+   <ul>
+     <li><b>PReP (PowerPC Reference Platform)</b>
+   </ul>
  </ul>
- <p>
+ <p>There is code in GXemul for emulation of many other machine types; the
- There is code in GXemul for emulation of many other machine types;
+ degree to which these work range from almost being able to run a complete
- the degree to which these work range from "almost" being able to run
+ OS, to almost completely unsupported (perhaps just enough support to
- a complete OS, to almost completely unsupported (perhaps just enough
+ output a few boot messages via serial console).
- support to output a few boot messages via serial console).
+ <p>In addition to emulating real machines, there is also a "test-machine".
- <p>
+ A test-machine consists of one or more CPUs and a few experimental devices
- In addition to emulating real machines, there is also a "test-machine".
+ such as:
- 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>.
-Line 352 
 You can read more about these experiment
+Line 346 
 You can read more about these experiment
  <p><br>
  <a name="guestos"></a>
- <h3>Which guest OSes are possible to run?</h3>
+ <h3>Which guest OSes are possible to run in GXemul?</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
-Line 433 
 interacted with similar to a real machin
+Line 427 
 interacted with similar to a real machin
                  <br>Cobalt</td>
          </tr>
+         <tr><td height="10"></td></tr>
+         <tr>
+           <td></td>
+           <td align="center"><a href="20050626-netbsd-sgimips-netboot.png"><img src="20050626-netbsd-sgimips-netboot_small.png"></a></td>
+           <td></td>
+           <td><a href="http://www.netbsd.org/Ports/sgimips/">NetBSD/sgimips</a>
+                 <br>SGI O2 ("IP32")</td>
+           <td></td>
+           <td align="center"><a href="20050622-netbsd-evbmips-malta.png"><img src="20050622-netbsd-evbmips-malta_small.png"></a></td>
+           <td></td>
+           <td><a href="http://www.netbsd.org/Ports/evbmips/">NetBSD/evbmips</a>
+                 <br>5Kc (and 4Kc) Malta<br>evaluation boards</td>
+           <td></td>
+         </tr>
+         <tr><td height="10"></td></tr>
+         <tr>
+           <td></td>
+           <td align="center"><a href="20051007-netbsd-cats-installed.png"><img src="20051007-netbsd-cats-installed_small.png"></a></td>
+           <td></td>
+           <td><a href="http://www.netbsd.org/Ports/cats/">NetBSD/cats</a>
+                 <br>CATS</td>
+           <td></td>
+           <td align="center"><a href="20051007-openbsd-cats-installed.png"><img src="20051007-openbsd-cats-installed_small.png"></a></td>
+           <td></td>
+           <td><a href="http://www.openbsd.org/cats.html">OpenBSD/cats</a>
+                 <br>CATS</td>
+           <td></td>
+         </tr>
+         <tr><td height="10"></td></tr>
+         <tr>
+           <td></td>
+           <td align="center"><a href="20051123-netbsd-prep.png"><img src="20051123-netbsd-prep_small.png"></a></td>
+           <td></td>
+           <td><a href="http://www.netbsd.org/Ports/prep/">NetBSD/prep</a>
+                 <br>PReP</td>
+           <td></td>
+         </tr>
  </table></center>

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