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This is repository of my old source code which isn't updated any more. Go to git.rot13.org for current projects!

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-revision 20 by dpavlin,
Mon Oct  8 16:19:23 2007 UTC
+revision 34 by dpavlin,
Mon Oct  8 16:21:17 2007 UTC
 Line 4
  <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>Gavare's eXperimental Emulator:&nbsp;&nbsp;&nbsp;</b></font>
+ <b>Gavare's eXperimental Emulator:</b></font><br>
  <font color="#000000" size="6"><b>Introduction</b>
  </font></td></tr></table></td></tr></table><p>
  <!--
- $Id: intro.html,v 1.66 2005/11/23 22:03:24 debug Exp $
+ $Id: intro.html,v 1.106 2007/02/18 09:19:47 debug Exp $
- Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.
+ Copyright (C) 2003-2007  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 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="#run">How to run the emulator</a>
-   <li><a href="#cpus">Which CPU types does GXemul emulate?</a>
+   <li><a href="#cpus">Which processor architectures does GXemul emulate?</a>
+   <li><a href="#hosts">Which host architectures are supported?</a>
+   <li><a href="#translation">What kind of translation does GXemul use?</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 in GXemul?</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 69 
 emulation modes are available. In some m
+Line 73 
 emulation modes are available. In some m
  hardware components are emulated well enough to let unmodified operating
  systems (e.g. NetBSD) run as if they were running on a real machine.
- <p>The processor architecture best emulated by GXemul is MIPS, but other
+ <p>Devices and processors are not simulated with 100% accuracy. They are
- architectures such as ARM and PowerPC are also partially emulated.
+ only ``faked'' well enough to allow guest operating systems to run without
+ complaining too much. 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>The emulator is written in C, does not depend on third-party libraries
+ <p>The emulator is written in C, does not depend on third-party libraries,
- (except X11, but that is optional), and should compile and run on most
+ and should compile and run on most 64-bit and 32-bit Unix-like systems.
- Unix-like systems.
  <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
 Line 95 
 even actual ROM images. A couple of diff
  <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
+ image. (This works for example with DECstation emulation, Dreamcast
- from ISO9660 CDROM images.)
+ emulation, or when booting from generic ISO9660 CDROM images if the
+ kernel is included in the image as a plain file.)
+ <p>Thanks to (in no specific order) Joachim Buss, Olivier Houchard, Juli
+ Mallett, Juan Romero Pardines, Alec Voropay, G�ran Weinholt, Alexander
+ Yurchenko, and everyone else who has provided me with feedback.
-Line 133 
 without source code. You need to check a
+Line 137 
 without source code. You need to check a
  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,
+ <p>In case you want to reuse parts of GXemul, but you need to do that
- and it is clear which version of GXemul was used to build the package,
+ under a different license (e.g. the GPL), then contact me and I might
- then it can be argued that the source code is available, just not in that
+ re-license/dual-license files on a case-by-case basis.
- specific package. Common sense should be used in this case, and not
- pedanticism.)
-Line 154 
 Uncompress the .tar.gz distribution file
+Line 155 
 Uncompress the .tar.gz distribution file
          $ <b>make</b>
  </pre>
- <p>This should work on most Unix-like systems. If it doesn't, then
+ <p>This should work on most Unix-like systems. GXemul does not require any
- mail me a bug report.
+ specific libraries to build, however, if you build on a system which does
+ not have X11 libraries installed, some functionality will be lost.
  <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 an AMD Athlon
- host, you might want to try setting <tt>CFLAGS</tt> to <tt>-march=athlon
+ host, you might want to try setting <tt>CFLAGS</tt> to <tt>-march=athlon</tt>
- -O3</tt> before running <tt>configure</tt>.
+ before running <tt>configure</tt>.
-Line 212 
 their original meaning in those xterm wi
+Line 214 
 their original meaning in those xterm wi
  <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>
+ The architectures that are emulated well enough to let at least one
+ guest operating system run (per architecture) are ARM, MIPS, PowerPC,
+ and SuperH.
+ <p>Please read the page about <a href="guestoses.html">guest operating
+ systems</a> for more information about the machines and operating systems
+ that can be considered "working" in the emulator.
- 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. Several guest operating systems for MIPS can run inside
- the emulator.
- <p>(For MIPS emulation, I have written an experimental dynamic binary
- translation subsystem, for Alpha and i386 hosts. This gives higher total
- performance than interpreting one instruction at a time and executing it.
- 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 2.1 and OpenBSD/cats 3.8,
- but it is not as tested or fine-tuned as the MIPS emulation mode.
- <h4>PowerPC:</h4>
- PowerPC emulation is still in its beginning stages, but good enough
+ <p><br>
- to run NetBSD/prep 2.1.
+ <a name="hosts"></a>
+ <h3>Which host architectures are supported?</h3>
+ GXemul should compile and run on any modern host architecture (64-bit or
+-bit word-length).
+ <p>Note: The dynamic translation engine does <i>not</i> require backends
+ for native code generation to be written for each individual host
+ architecture; the "intermediate representation" that the dyntrans system
+ uses can be executed on any host architecture.
+ <p><br>
+ <a name="translation"></a>
+ <h3>What kind of translation does GXemul use?</h3>
+ <b>Static vs. dynamic:</b>
+ <p>In order to support guest operating systems, which can overwrite old
+ code pages in memory with new code, it is necessary to translate code
+ dynamically. It is not possible to do a "one-pass" (static) translation.
+ Self-modifying code and Just-in-Time compilers running inside
+ the emulator are other things that would not work with a static
+ translator. GXemul is a dynamic translator. However, it does not
+ necessarily translate into native code, like many other emulators.
+ <p><b>"Runnable" Intermediate Representation:</b>
+ <p>Dynamic translators usually translate from the emulated architecture
+ (e.g. MIPS) into a kind of <i>intermediate representation</i> (IR), and then
+ to native code (e.g. AMD64 or x86 code). Since one of my main goals for
+ GXemul is to keep everything as portable as possible, I have tried to make
+ sure that the IR is something which can be executed regardless of whether
+ the final step (translation from IR to native code) has been implemented
+ or not.
+ <p>The IR in GXemul consists of arrays of pointers to functions, and a few
+ arguments which are passed along to those functions. The functions are
+ implemented in either manually hand-coded C, or automatically generated C.
+ In any case, this is all statically linked into the GXemul binary at link
+ time.
+ <p>Here is a simplified diagram of how these arrays work.
+ <p><center><img src="simplified_dyntrans.png"></center>
+ <p>There is one instruction call slot for every possible program counter
+ location. In the MIPS case, instruction words are 32 bits in length,
+ and pages are (usually) 4 KB large, resulting in 1024 instruction call
+ slots. After the last of these instruction calls, there is an additional
+ call to a special "end of page" function (which doesn't count as an executed
+ instruction). This function switches to the first instruction
+ on the next virtual page (which might cause exceptions, etc).
+ <p>The complexity of individual instructions vary. A simple example of
+ what an instruction can look like is the MIPS <tt>addiu</tt> instruction:
+ <pre>
+         X(addiu)
+         {
+                 reg(ic->arg[1]) = (int32_t)
+                     ((int32_t)reg(ic->arg[0]) + (int32_t)ic->arg[2]);
+         }
+ </pre>
+ <p>It stores the result of a 32-bit addition of the register at arg[0]
+ with the immediate value arg[2] (treating both as signed 32-bit
+ integers) into register arg[1]. If the emulated CPU is a 64-bit CPU,
+ then this will store a correctly sign-extended value into arg[1].
+ If it is a 32-bit CPU, then only the lowest 32 bits will be stored,
+ and the high part ignored. <tt>X(addiu)</tt> is expanded to
+ <tt>mips_instr_addiu</tt> in the 64-bit case, and <tt>mips32_instr_addiu</tt>
+ in the 32-bit case. Both are compiled into the GXemul executable; no code
+ is created during run-time.
+ <p>Here are examples of what the <tt>addiu</tt> instruction actually
+ looks like when it is compiled, on various host architectures:
+ <p><center><table border="0">
+     <tr><td><b>GCC 4.0.1 on Alpha:</b></td>
+         <td width="35"></td><td></td>
+     <tr>
+         <td valign="top">
+ <pre>mips_instr_addiu:
+      ldq     t1,8(a1)
+      ldq     t2,24(a1)
+      ldq     t3,16(a1)
+      ldq     t0,0(t1)
+      addl    t0,t2,t0
+      stq     t0,0(t3)
+      ret</pre>
+         </td>
+         <td></td>
+         <td valign="top">
+ <pre>mips32_instr_addiu:
+      ldq     t2,8(a1)
+      ldq     t0,24(a1)
+      ldq     t3,16(a1)
+      ldl     t1,0(t2)
+      addq    t0,t1,t0
+      stl     t0,0(t3)
+      ret</pre>
+         </td>
+     </tr>
+     <tr><td><b><br>GCC 3.4.4 on AMD64:</b></td>
+     <tr>
+         <td valign="top">
+ <pre>mips_instr_addiu:
+      mov    0x8(%rsi),%rdx
+      mov    0x18(%rsi),%rax
+      mov    0x10(%rsi),%rcx
+      add    (%rdx),%eax
+      cltq
+      mov    %rax,(%rcx)
+      retq</pre>
+         </td>
+         <td></td>
+         <td valign="top">
+ <pre>mips32_instr_addiu:
+      mov    0x8(%rsi),%rcx
+      mov    0x10(%rsi),%rdx
+      mov    (%rcx),%eax
+      add    0x18(%rsi),%eax
+      mov    %eax,(%rdx)
+      retq</pre>
+         </td>
+     </tr>
+     <tr><td><b><br>GCC 4.0.1 on i386:</b></td>
+     <tr>
+         <td valign="top">
+ <pre>mips_instr_addiu:
+      mov    0x8(%esp),%eax
+      mov    0x8(%eax),%ecx
+      mov    0x4(%eax),%edx
+      mov    0xc(%eax),%eax
+      add    (%edx),%eax
+      mov    %eax,(%ecx)
+      cltd
+      mov    %edx,0x4(%ecx)
+      ret</pre>
+         </td>
+         <td></td>
+         <td valign="top">
+ <pre>mips32_instr_addiu:
+      mov    0x8(%esp),%eax
+      mov    0x8(%eax),%ecx
+      mov    0x4(%eax),%edx
+      mov    0xc(%eax),%eax
+      add    (%edx),%eax
+      mov    %eax,(%ecx)
+      ret</pre>
+         </td>
+     </tr>
+ </table></center>
+ <p>On 64-bit hosts, there is not much difference, but on 32-bit hosts (and
+ to some extent on AMD64), the difference is enough to make it worthwhile.
+ <p><b>Performance:</b>
+ <p>The performance of using this kind of runnable IR is obviously lower
+ than what can be achieved by emulators using native code generation, but
+ can be significantly higher than using a naive fetch-decode-execute
+ interpretation loop. In my opinion, using a runnable IR is an interesting
+ compromise.
+ <p>The overhead per emulated instruction is usually around or below
+ approximately 10 host instructions. This is very much dependent on your
+ host architecture and what compiler and compiler switches you are using.
+ Added to this instruction count is (of course) also the C code used to
+ implement each specific instruction.
+ <p><b>Instruction Combinations:</b>
+ <p>Short, common instruction sequences can sometimes be replaced by a
+ "compound" instruction. An example could be a compare instruction followed
+ by a conditional branch instruction. The advantages of instruction
+ combinations are that
+ <ul>
+   <li>the amortized overhead per instruction is slightly reduced, and
+   <p>
+   <li>the host's compiler can make a good job at optimizing the common
+         instruction sequence.
+ </ul>
+ <p>The special cases where instruction combinations give the most gain
+ are in the cores of string/memory manipulation functions such as
+ <tt>memset()</tt> or <tt>strlen()</tt>. The core loop can then (at least
+ to some extent) be replaced by a native call to the equivalent function.
+ <p>The implementations of compound instructions still keep track of the
+ number of executed instructions, etc. When single-stepping, these
+ translations are invalidated, and replaced by normal instruction calls
+ (one per emulated instruction).
+ <p><b>Native Code Back-ends:</b>
+ <p>In theory, it will be possible to implement native code generation,
+ similar to what is used in high-performance emulators such as QEMU,
+ as long as that generated code abides to the C ABI on the host.
+ <p>However, since I wanted to make sure that GXemul works without such
+ native code back-ends, there are no implemented backends in this release.
+ <p>(There is a place-holder in the source code for native code generation,
+ which can be used for experiments, but it does not contain any working
+ code at the moment.)
- <p>Non-MIPS emulation modes use dynamic translation, but not recompilation
- into native code. This makes it possible to run on any host platform.
-Line 249 
 into native code. This makes it possible
+Line 453 
 into native code. This makes it possible
  <h3>Emulation accuracy:</h3>
  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
+ several steps within a real CPU are not taken into account (e.g. pipe-line
  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
+ <p>The existance of instruction and data caches is "faked" to let
- caches is "faked" to let operating systems think that they are there.
+ operating systems think that they are there, but for all practical
- (There is some old code for R2000/R3000 caches, but it has probably
+ purposes, these caches are non-working.
- suffered from bitrot by now.)
+ <p>The emulator is in general <i>not</i> timing-accurate, neither at the
- <p>The emulator is <i>not</i> timing-accurate. It can be run in a
+ instruction level nor on any higher level. An attempt is made to let
- "deterministic" mode, <tt><b>-D</b></tt>. The meaning of deterministic is
+ emulated clocks run at the same speed as the host (i.e. an emulated timer
- simply that running two emulations with the same settings will result in
+ running at 100 Hz will interrupt around 100 times per real second), but
- identical runs. Obviously, this requires that no user interaction is
+ since the host speed may vary, e.g. because of other running processes,
- taking place, and that clock speeds are fixed with the <tt><b>-I</b></tt>
+ there is no guarantee as to how many instructions will be executed in
- option. (Deterministic in this case does <i>not</i> mean that the
+ each of these 100 Hz cycles.
- emulation will be identical to some actual real-world machine.)
+ <p>If the host is very slow, the emulated clocks might even lag behind
- <p><font color="#ff0000">(Oops/TODO: User interaction means <i>both</i>
+ the real-world clock.
- 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 286 
 are emulated well enough to run at least
+Line 487 
 are emulated well enough to run at least
  <p>
  <ul>
-   <li><b><u>MIPS</u></b>
+   <li><b><u>ARM</u></b>
    <ul>
-     <li><b>DECstation 5000/200</b>&nbsp;&nbsp;("3max")
+     <li><b>CATS</b> (<a href="guestoses.html#netbsdcatsinstall">NetBSD/cats</a>,
-     <p>
+         <a href="guestoses.html#openbsdcatsinstall">OpenBSD/cats</a>)
-     <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)
+     <li><b>IQ80321</b> (<a href="guestoses.html#netbsdevbarminstall">NetBSD/evbarm</a>)
-     <p>
+     <li><b>NetWinder</b> (<a href="guestoses.html#netbsdnetwinderinstall">NetBSD/netwinder</a>)
-     <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><u>ARM</u></b>
+   <li><b><u>MIPS</u></b>
    <ul>
-     <li><b>CATS</b>
+     <li><b>DECstation 5000/200</b> (<a href="guestoses.html#netbsdpmaxinstall">NetBSD/pmax</a>,
+         <a href="guestoses.html#openbsdpmaxinstall">OpenBSD/pmax</a>,
+         <a href="guestoses.html#ultrixinstall">Ultrix</a>,
+         <a href="guestoses.html#declinux">Linux/DECstation</a>,
+         <a href="guestoses.html#sprite">Sprite</a>)
+     <li><b>Acer Pica-61</b> (<a href="guestoses.html#netbsdarcinstall">NetBSD/arc</a>)
+     <li><b>NEC MobilePro 770, 780, 800, 880</b> (<a href="guestoses.html#netbsdhpcmipsinstall">NetBSD/hpcmips</a>)
+     <li><b>Cobalt</b> (<a href="guestoses.html#netbsdcobaltinstall">NetBSD/cobalt</a>)
+     <li><b>Malta</b> (<a href="guestoses.html#netbsdevbmipsinstall">NetBSD/evbmips</a>, Linux/Malta <font color="#0000e0">(<super>*1</super>)</font>)
+     <li><b>Algorithmics P5064</b> (<a href="guestoses.html#netbsdalgorinstall">NetBSD/algor</a>)
+     <li><b>SGI O2 (aka IP32)</b> <font color="#0000e0">(<super>*2</super>)</font>
+         (<a href="guestoses.html#netbsdsgimips">NetBSD/sgi</a>)
    </ul>
    <p>
    <li><b><u>PowerPC</u></b>
    <ul>
-     <li><b>PReP (PowerPC Reference Platform)</b>
+     <li><b>IBM 6050/6070 (PReP, PowerPC Reference Platform)</b> (<a href="guestoses.html#netbsdprepinstall">NetBSD/prep</a>)
+     <li><b>MacPPC (generic "G4" Macintosh)</b> (<a href="guestoses.html#netbsdmacppcinstall">NetBSD/macppc</a>)
+   </ul>
+   <p>
+   <li><b><u>SuperH</u></b>
+   <ul>
+     <li><b>Sega Dreamcast</b> (<a href="dreamcast.html#netbsd_generic_md">NetBSD/dreamcast</a>)
    </ul>
  </ul>
+ <p>
+ <small><font color="#0000e0">(<super>*1</super>)</font> =
+ Linux/Malta may be run as a guest OS, however I have not yet found any stable
+ URL to pre-compiled Linux/Malta kernels. Thus, Linux/Malta emulation is not
+ tested for every release of the emulator; sometimes it works, sometimes
+ it doesn't.</small>
+ <br><small><font color="#0000e0">(<super>*2</super>)</font> =
+ SGI O2 emulation is enough for root-on-nfs, but not for disk boot.</small>
  <p>There is code in GXemul for emulation of many other machine types; 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
-Line 327 
 such as:
+Line 548 
 such as:
    <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 disk controller
    <li>a simple ethernet controller
+   <li>a real-time clock device
  </ul>
  <p>This mode is useful if you wish to run experimental code, but do not
-Line 343 
 href="experiments.html#expdevices">here<
+Line 565 
 href="experiments.html#expdevices">here<
- <p><br>
- <a name="guestos"></a>
- <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
- interacted with similar to a real machine.
- <p>
- <center><table border="0">
-         <tr>
-           <td width="10"></td>
-           <td align="center"><a href="20050317-example.png"><img src="20050317-example_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>
-         <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>
- <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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