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1  <html>  <html><head><title>Gavare's eXperimental Emulator:&nbsp;&nbsp;&nbsp;Introduction</title>
2  <head><title>GXemul documentation: Introduction</title>  <meta name="robots" content="noarchive,nofollow,noindex"></head>
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3  <body bgcolor="#f8f8f8" text="#000000" link="#4040f0" vlink="#404040" alink="#ff0000">  <body bgcolor="#f8f8f8" text="#000000" link="#4040f0" vlink="#404040" alink="#ff0000">
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5  <td width=100% align=center valign=center><table border=0 width=100%><tr>  <td width=100% align=center valign=center><table border=0 width=100%><tr>
6  <td align="left" valign=center bgcolor="#d0efff"><font color="#6060e0" size="6">  <td align="left" valign=center bgcolor="#d0efff"><font color="#6060e0" size="6">
7  <b>GXemul documentation:</b></font>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  <b>Gavare's eXperimental Emulator:</b></font><br>
8  <font color="#000000" size="6"><b>Introduction</b>  <font color="#000000" size="6"><b>Introduction</b>
9  </font></td></tr></table></td></tr></table><p>  </font></td></tr></table></td></tr></table><p>
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13  $Id: intro.html,v 1.46 2005/06/04 12:02:17 debug Exp $  $Id: intro.html,v 1.106 2007/02/18 09:19:47 debug Exp $
14    
15  Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.  Copyright (C) 2003-2007  Anders Gavare.  All rights reserved.
16    
17  Redistribution and use in source and binary forms, with or without  Redistribution and use in source and binary forms, with or without
18  modification, are permitted provided that the following conditions are met:  modification, are permitted provided that the following conditions are met:
# Line 48  SUCH DAMAGE. Line 45  SUCH DAMAGE.
45  <h2>Introduction</h2>  <h2>Introduction</h2>
46    
47  <p>  <p>
48    <table border="0" width="99%"><tr><td valign="top" align="left">
49  <ul>  <ul>
50    <li><a href="#overview">Overview</a>    <li><a href="#overview">Overview</a>
51    <li><a href="#free">Is GXemul Free software?</a>    <li><a href="#free">Is GXemul Free software?</a>
52    <li><a href="#build">How to compile/build the emulator</a>    <li><a href="#build">How to compile/build the emulator</a>
53    <li><a href="#run">How to run the emulator</a>    <li><a href="#run">How to run the emulator</a>
54    <li><a href="#cpus">Which CPU types does GXemul emulate?</a>    <li><a href="#cpus">Which processor architectures does GXemul emulate?</a>
55      <li><a href="#hosts">Which host architectures are supported?</a>
56      <li><a href="#translation">What kind of translation does GXemul use?</a>
57    <li><a href="#accuracy">Emulation accuracy</a>    <li><a href="#accuracy">Emulation accuracy</a>
58    <li><a href="#emulmodes">Which machines does GXemul emulate?</a>    <li><a href="#emulmodes">Which machines does GXemul emulate?</a>
   <li><a href="#guestos">Which guest OSes are possible to run?</a>  
59  </ul>  </ul>
60    </td><td valign="center" align="center">
61    <a href="20050317-example.png"><img src="20050317-example_small.png"></a>
62    <p>NetBSD/pmax 1.6.2 with X11<br>running in GXemul</td></tr></table>
63    
64    
65    
# Line 67  SUCH DAMAGE. Line 68  SUCH DAMAGE.
68  <a name="overview"></a>  <a name="overview"></a>
69  <h3>Overview:</h3>  <h3>Overview:</h3>
70    
71  GXemul is a machine emulator, which can be used to experiment with  GXemul is an experimental instruction-level machine emulator. Several
72  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  
73  hardware components are emulated well enough to let unmodified operating  hardware components are emulated well enough to let unmodified operating
74  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.
75    
76  <p>  <p>Devices and processors are not simulated with 100% accuracy. They are
77  Devices and CPUs are not simulated with 100% accuracy. They are only  only ``faked'' well enough to allow guest operating systems to run without
78  "faked" well enough to make operating systems (eg NetBSD) run without  complaining too much. Still, the emulator could be of interest for
79  complaining too much. Still, the emulator could be of interest for  academic research and experiments, such as when learning how to write
 academic research and experiments, such as when learning how to write  
80  operating system code.  operating system code.
81    
82  <p>  <p>The emulator is written in C, does not depend on third-party libraries,
83  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.)  
84    
85  <p>  <p>The emulator contains code which tries to emulate the workings of CPUs
86  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
87  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
88  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  
89  emulator itself, so you do not need to use any ROM image at all.  emulator itself, so you do not need to use any ROM image at all.
90    
91  <p>  <p>You can use pre-compiled kernels (for example NetBSD kernels, or
92  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
93  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
94  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).  
95    
96  <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  
97  disk image, then it is sometimes possible to boot directly from that  disk image, then it is sometimes possible to boot directly from that
98  image. (This works for example with DECstation emulation, or when booting  image. (This works for example with DECstation emulation, Dreamcast
99  from ISO9660 CDROM images.)  emulation, or when booting from generic ISO9660 CDROM images if the
100    kernel is included in the image as a plain file.)
101    
102    <p>Thanks to (in no specific order) Joachim Buss, Olivier Houchard, Juli
103    Mallett, Juan Romero Pardines, Alec Voropay, Göran Weinholt, Alexander
104    Yurchenko, and everyone else who has provided me with feedback.
105    
106    
107    
108    
# Line 122  confusing to you, you might want to read Line 119  confusing to you, you might want to read
119  four freedoms associated with Free software, <a  four freedoms associated with Free software, <a
120  href="http://www.gnu.org/philosophy/free-sw.html">http://www.gnu.org/philosophy/free-sw.html</a>.)  href="http://www.gnu.org/philosophy/free-sw.html">http://www.gnu.org/philosophy/free-sw.html</a>.)
121    
122  <p>  <p>The code I have written is released under a 3-clause BSD-style license
123  The code I have written is released under a 3-clause BSD-style license  (or "revised BSD-style" if one wants to use <a
124  (or "revised BSD-style" if one wants to use  href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>). Apart from
125  <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
126  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
127  such as NetBSD, for example header files containing symbolic names of  device registers. They are also covered by similar licenses, but with some
128  bitfields in device registers. They are also covered by similar licenses,  additional clauses. The main point, however, is that the licenses require
129  but with some additional clauses. If you plan to redistribute GXemul  that the original Copyright and license terms are included when you make a
130  (for example as a binary package), or reuse code from GXemul,  copy or modification.
131  then you should check those files for their license terms.  
132    <p>If you plan to redistribute GXemul <i>without</i> supplying the source
133  <p>  code, then you need to comply with each individual source file some other
134  (The licenses usually require that the original Copyright and license  way, for example by writing additional documentation containing copyright
135  terms are included when you make a copy or modification. The "easiest way  notes. I have not done this, since I do not plan on making distributions
136  out" if you plan to redistribute code from GXemul is to simply supply  without source code. You need to check all individual files for details.
137  the source code. You should however check individual files for details.)  The "easiest way out" if you plan to redistribute code from GXemul is, of
138    course, to let it remain open source and simply supply the source code.
139    
140    <p>In case you want to reuse parts of GXemul, but you need to do that
141    under a different license (e.g. the GPL), then contact me and I might
142    re-license/dual-license files on a case-by-case basis.
143    
144    
145    
# Line 153  Uncompress the .tar.gz distribution file Line 155  Uncompress the .tar.gz distribution file
155          $ <b>make</b>          $ <b>make</b>
156  </pre>  </pre>
157    
158  <p>  <p>This should work on most Unix-like systems. GXemul does not require any
159  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
160  mail me a bug report.  not have X11 libraries installed, some functionality will be lost.
161    
162  <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  
163  and on compiler settings, so you might want to experiment with different  and on compiler settings, so you might want to experiment with different
164  CC and CFLAGS environment variable values. For example, on a modern PC,  CC and CFLAGS environment variable values. For example, on an AMD Athlon
165  you could try the following:  host, you might want to try setting <tt>CFLAGS</tt> to <tt>-march=athlon</tt>
166  <p>  before running <tt>configure</tt>.
 <pre>  
         $ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b>  
         $ <b>make</b>  
 </pre>  
167    
 <p>  
 Run <b><tt>./configure --help</tt></b> to get a list of configure options. (The  
 possible options differ between different releases and snapshots.)  
168    
169    
170    
# Line 224  their original meaning in those xterm wi Line 214  their original meaning in those xterm wi
214    
215  <p><br>  <p><br>
216  <a name="cpus"></a>  <a name="cpus"></a>
217  <h3>Which CPU types does GXemul emulate?</h3>  <h3>Which processor architectures does GXemul emulate?</h3>
218    
219    The architectures that are emulated well enough to let at least one
220    guest operating system run (per architecture) are ARM, MIPS, PowerPC,
221    and SuperH.
222    
223    <p>Please read the page about <a href="guestoses.html">guest operating
224    systems</a> for more information about the machines and operating systems
225    that can be considered "working" in the emulator.
226    
227    
228    
229    
230    
231    
232    <p><br>
233    <a name="hosts"></a>
234    <h3>Which host architectures are supported?</h3>
235    
236    GXemul should compile and run on any modern host architecture (64-bit or
237    32-bit word-length).
238    
239    <p>Note: The dynamic translation engine does <i>not</i> require backends
240    for native code generation to be written for each individual host
241    architecture; the "intermediate representation" that the dyntrans system
242    uses can be executed on any host architecture.
243    
 <h4>MIPS:</h4>  
244    
 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.  
245    
 <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.)  
246    
247    
248  <h4>URISC:</h4>  <p><br>
249    <a name="translation"></a>
250    <h3>What kind of translation does GXemul use?</h3>
251    
252    <b>Static vs. dynamic:</b>
253    
254  I have implemented an <a href="http://en.wikipedia.org/wiki/URISC">URISC</a>  <p>In order to support guest operating systems, which can overwrite old
255  emulation mode, just for fun. The only instruction available in an URISC  code pages in memory with new code, it is necessary to translate code
256  machine is "reverse subtract and skip on borrow". (It is probably not  dynamically. It is not possible to do a "one-pass" (static) translation.
257  worth trying to do bintrans with URISC, because any reasonable URISC  Self-modifying code and Just-in-Time compilers running inside
258  program relies on self-modifying code, which is bad for bintrans  the emulator are other things that would not work with a static
259  performance.)  translator. GXemul is a dynamic translator. However, it does not
260    necessarily translate into native code, like many other emulators.
261    
262    <p><b>"Runnable" Intermediate Representation:</b>
263    
264    <p>Dynamic translators usually translate from the emulated architecture
265    (e.g. MIPS) into a kind of <i>intermediate representation</i> (IR), and then
266    to native code (e.g. AMD64 or x86 code). Since one of my main goals for
267    GXemul is to keep everything as portable as possible, I have tried to make
268    sure that the IR is something which can be executed regardless of whether
269    the final step (translation from IR to native code) has been implemented
270    or not.
271    
272    <p>The IR in GXemul consists of arrays of pointers to functions, and a few
273    arguments which are passed along to those functions. The functions are
274    implemented in either manually hand-coded C, or automatically generated C.
275    In any case, this is all statically linked into the GXemul binary at link
276    time.
277    
278    <p>Here is a simplified diagram of how these arrays work.
279    
280    <p><center><img src="simplified_dyntrans.png"></center>
281    
282    <p>There is one instruction call slot for every possible program counter
283    location. In the MIPS case, instruction words are 32 bits in length,
284    and pages are (usually) 4 KB large, resulting in 1024 instruction call
285    slots. After the last of these instruction calls, there is an additional
286    call to a special "end of page" function (which doesn't count as an executed
287    instruction). This function switches to the first instruction
288    on the next virtual page (which might cause exceptions, etc).
289    
290    <p>The complexity of individual instructions vary. A simple example of
291    what an instruction can look like is the MIPS <tt>addiu</tt> instruction:
292    <pre>
293            X(addiu)
294            {
295                    reg(ic->arg[1]) = (int32_t)
296                        ((int32_t)reg(ic->arg[0]) + (int32_t)ic->arg[2]);
297            }
298    </pre>
299    
300  <h4>POWER/PowerPC</h4>  <p>It stores the result of a 32-bit addition of the register at arg[0]
301    with the immediate value arg[2] (treating both as signed 32-bit
302    integers) into register arg[1]. If the emulated CPU is a 64-bit CPU,
303    then this will store a correctly sign-extended value into arg[1].
304    If it is a 32-bit CPU, then only the lowest 32 bits will be stored,
305    and the high part ignored. <tt>X(addiu)</tt> is expanded to
306    <tt>mips_instr_addiu</tt> in the 64-bit case, and <tt>mips32_instr_addiu</tt>
307    in the 32-bit case. Both are compiled into the GXemul executable; no code
308    is created during run-time.
309    
310    <p>Here are examples of what the <tt>addiu</tt> instruction actually
311    looks like when it is compiled, on various host architectures:
312    
313    <p><center><table border="0">
314        <tr><td><b>GCC 4.0.1 on Alpha:</b></td>
315            <td width="35"></td><td></td>
316        <tr>
317            <td valign="top">
318    <pre>mips_instr_addiu:
319         ldq     t1,8(a1)
320         ldq     t2,24(a1)
321         ldq     t3,16(a1)
322         ldq     t0,0(t1)
323         addl    t0,t2,t0
324         stq     t0,0(t3)
325         ret</pre>
326            </td>
327            <td></td>
328            <td valign="top">
329    <pre>mips32_instr_addiu:
330         ldq     t2,8(a1)
331         ldq     t0,24(a1)
332         ldq     t3,16(a1)
333         ldl     t1,0(t2)
334         addq    t0,t1,t0
335         stl     t0,0(t3)
336         ret</pre>
337            </td>
338        </tr>
339    
340        <tr><td><b><br>GCC 3.4.4 on AMD64:</b></td>
341        <tr>
342            <td valign="top">
343    <pre>mips_instr_addiu:
344         mov    0x8(%rsi),%rdx
345         mov    0x18(%rsi),%rax
346         mov    0x10(%rsi),%rcx
347         add    (%rdx),%eax
348         cltq
349         mov    %rax,(%rcx)
350         retq</pre>
351            </td>
352            <td></td>
353            <td valign="top">
354    <pre>mips32_instr_addiu:
355         mov    0x8(%rsi),%rcx
356         mov    0x10(%rsi),%rdx
357         mov    (%rcx),%eax
358         add    0x18(%rsi),%eax
359         mov    %eax,(%rdx)
360         retq</pre>
361            </td>
362        </tr>
363    
364        <tr><td><b><br>GCC 4.0.1 on i386:</b></td>
365        <tr>
366            <td valign="top">
367    <pre>mips_instr_addiu:
368         mov    0x8(%esp),%eax
369         mov    0x8(%eax),%ecx
370         mov    0x4(%eax),%edx
371         mov    0xc(%eax),%eax
372         add    (%edx),%eax
373         mov    %eax,(%ecx)
374         cltd
375         mov    %edx,0x4(%ecx)
376         ret</pre>
377            </td>
378            <td></td>
379            <td valign="top">
380    <pre>mips32_instr_addiu:
381         mov    0x8(%esp),%eax
382         mov    0x8(%eax),%ecx
383         mov    0x4(%eax),%edx
384         mov    0xc(%eax),%eax
385         add    (%edx),%eax
386         mov    %eax,(%ecx)
387         ret</pre>
388            </td>
389        </tr>
390    </table></center>
391    
392  There is some code for 64-bit (and 32-bit) POWER/PowerPC emulation, enough  <p>On 64-bit hosts, there is not much difference, but on 32-bit hosts (and
393  to run "Hello World", but not enough to run complete operating systems.    to some extent on AMD64), the difference is enough to make it worthwhile.
 This mode isn't really working yet.  
394    
395    
396  <h4>Other CPU types:</h4>  <p><b>Performance:</b>
397    
398    <p>The performance of using this kind of runnable IR is obviously lower
399    than what can be achieved by emulators using native code generation, but
400    can be significantly higher than using a naive fetch-decode-execute
401    interpretation loop. In my opinion, using a runnable IR is an interesting
402    compromise.
403    
404    <p>The overhead per emulated instruction is usually around or below
405    approximately 10 host instructions. This is very much dependent on your
406    host architecture and what compiler and compiler switches you are using.
407    Added to this instruction count is (of course) also the C code used to
408    implement each specific instruction.
409    
410    <p><b>Instruction Combinations:</b>
411    
412    <p>Short, common instruction sequences can sometimes be replaced by a
413    "compound" instruction. An example could be a compare instruction followed
414    by a conditional branch instruction. The advantages of instruction
415    combinations are that
416    <ul>
417      <li>the amortized overhead per instruction is slightly reduced, and
418      <p>
419      <li>the host's compiler can make a good job at optimizing the common
420            instruction sequence.
421    </ul>
422    
423    <p>The special cases where instruction combinations give the most gain
424    are in the cores of string/memory manipulation functions such as
425    <tt>memset()</tt> or <tt>strlen()</tt>. The core loop can then (at least
426    to some extent) be replaced by a native call to the equivalent function.
427    
428    <p>The implementations of compound instructions still keep track of the
429    number of executed instructions, etc. When single-stepping, these
430    translations are invalidated, and replaced by normal instruction calls
431    (one per emulated instruction).
432    
433    <p><b>Native Code Back-ends:</b>
434    
435    <p>In theory, it will be possible to implement native code generation,
436    similar to what is used in high-performance emulators such as QEMU,
437    as long as that generated code abides to the C ABI on the host.
438    
439    <p>However, since I wanted to make sure that GXemul works without such
440    native code back-ends, there are no implemented backends in this release.
441    
442    <p>(There is a place-holder in the source code for native code generation,
443    which can be used for experiments, but it does not contain any working
444    code at the moment.)
445    
 Some other CPU architectures (such as x86) can also be partially emulated.  
 These are not enabled by default though, because of their unstable-ness.  
446    
447    
448    
# Line 271  These are not enabled by default though, Line 453  These are not enabled by default though,
453  <h3>Emulation accuracy:</h3>  <h3>Emulation accuracy:</h3>
454    
455  GXemul is an instruction-level emulator; things that would happen in  GXemul is an instruction-level emulator; things that would happen in
456  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
457  stalls or out-of-order execution). Still, instruction-level accuracy seems  stalls or out-of-order execution). Still, instruction-level accuracy seems
458  to be enough to be able to run complete guest operating systems inside the  to be enough to be able to run complete guest operating systems inside the
459  emulator.  emulator.
460    
461  <p>  <p>The existance of instruction and data caches is "faked" to let
462  Caches are by default not emulated. In some cases, the existance of caches  operating systems think that they are there, but for all practical
463  is "faked" to let operating systems think that they are there. (There is  purposes, these caches are non-working.
464  some old code for R2000/R3000 caches, but it has probably suffered from  
465  bitrot by now.)  <p>The emulator is in general <i>not</i> timing-accurate, neither at the
466    instruction level nor on any higher level. An attempt is made to let
467    emulated clocks run at the same speed as the host (i.e. an emulated timer
468    running at 100 Hz will interrupt around 100 times per real second), but
469    since the host speed may vary, e.g. because of other running processes,
470    there is no guarantee as to how many instructions will be executed in
471    each of these 100 Hz cycles.
472    
473    <p>If the host is very slow, the emulated clocks might even lag behind
474    the real-world clock.
475    
 <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.)  
476    
477    
478    
# Line 304  are emulated well enough to run at least Line 487  are emulated well enough to run at least
487    
488  <p>  <p>
489  <ul>  <ul>
490    <li><b>DECstation 5000/200</b>&nbsp;&nbsp;("3max")    <li><b><u>ARM</u></b>
491          <br>Serial controller (including keyboard and mouse), ethernet,    <ul>
492          SCSI, and graphical framebuffers.      <li><b>CATS</b> (<a href="guestoses.html#netbsdcatsinstall">NetBSD/cats</a>,
493            <a href="guestoses.html#openbsdcatsinstall">OpenBSD/cats</a>)
494        <li><b>IQ80321</b> (<a href="guestoses.html#netbsdevbarminstall">NetBSD/evbarm</a>)
495        <li><b>NetWinder</b> (<a href="guestoses.html#netbsdnetwinderinstall">NetBSD/netwinder</a>)
496      </ul>
497    <p>    <p>
498    <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)    <li><b><u>MIPS</u></b>
499          <br>Serial controller, "VGA" text console, and SCSI.    <ul>
500        <li><b>DECstation 5000/200</b> (<a href="guestoses.html#netbsdpmaxinstall">NetBSD/pmax</a>,
501            <a href="guestoses.html#openbsdpmaxinstall">OpenBSD/pmax</a>,
502            <a href="guestoses.html#ultrixinstall">Ultrix</a>,
503            <a href="guestoses.html#declinux">Linux/DECstation</a>,
504            <a href="guestoses.html#sprite">Sprite</a>)
505        <li><b>Acer Pica-61</b> (<a href="guestoses.html#netbsdarcinstall">NetBSD/arc</a>)
506        <li><b>NEC MobilePro 770, 780, 800, 880</b> (<a href="guestoses.html#netbsdhpcmipsinstall">NetBSD/hpcmips</a>)
507        <li><b>Cobalt</b> (<a href="guestoses.html#netbsdcobaltinstall">NetBSD/cobalt</a>)
508        <li><b>Malta</b> (<a href="guestoses.html#netbsdevbmipsinstall">NetBSD/evbmips</a>, Linux/Malta <font color="#0000e0">(<super>*1</super>)</font>)
509        <li><b>Algorithmics P5064</b> (<a href="guestoses.html#netbsdalgorinstall">NetBSD/algor</a>)
510        <li><b>SGI O2 (aka IP32)</b> <font color="#0000e0">(<super>*2</super>)</font>
511            (<a href="guestoses.html#netbsdsgimips">NetBSD/sgi</a>)
512      </ul>
513    <p>    <p>
514    <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)    <li><b><u>PowerPC</u></b>
515          <br>Framebuffer, keyboard, and a PCMCIA IDE controller.    <ul>
516        <li><b>IBM 6050/6070 (PReP, PowerPC Reference Platform)</b> (<a href="guestoses.html#netbsdprepinstall">NetBSD/prep</a>)
517        <li><b>MacPPC (generic "G4" Macintosh)</b> (<a href="guestoses.html#netbsdmacppcinstall">NetBSD/macppc</a>)
518      </ul>
519    <p>    <p>
520    <li><b>Cobalt</b>    <li><b><u>SuperH</u></b>
521          <br>Serial controller and PCI IDE.    <ul>
522        <li><b>Sega Dreamcast</b> (<a href="dreamcast.html#netbsd_generic_md">NetBSD/dreamcast</a>)
523      </ul>
524  </ul>  </ul>
525    
526  <p>  <p>
527  There is code in GXemul for emulation of many other machine types;  <small><font color="#0000e0">(<super>*1</super>)</font> =
528  the degree to which these work range from "almost" being able to run  Linux/Malta may be run as a guest OS, however I have not yet found any stable
529  a complete OS, to almost completely unsupported (perhaps just enough  URL to pre-compiled Linux/Malta kernels. Thus, Linux/Malta emulation is not
530  support to output a few boot messages via serial console).  tested for every release of the emulator; sometimes it works, sometimes
531    it doesn't.</small>
532  <p>  
533  In addition to emulating real machines, there is also a "test-machine".  <br><small><font color="#0000e0">(<super>*2</super>)</font> =
534  A test-machine consists of one or more CPUs and a few experimental  SGI O2 emulation is enough for root-on-nfs, but not for disk boot.</small>
535  devices such as:  
536    
537    <p>There is code in GXemul for emulation of many other machine types; the
538    degree to which these work range from almost being able to run a complete
539    OS, to almost completely unsupported (perhaps just enough support to
540    output a few boot messages via serial console).
541    
542    <p>In addition to emulating real machines, there is also a "test-machine".
543    A test-machine consists of one or more CPUs and a few experimental devices
544    such as:
545    
546  <p>  <p>
547  <ul>  <ul>
548    <li>a console I/O device (putchar() and getchar()...)    <li>a console I/O device (putchar() and getchar()...)
549    <li>an inter-processor communication device, for SMP experiments    <li>an inter-processor communication device, for SMP experiments
550    <li>a very simple linear framebuffer device (for graphics output)    <li>a very simple linear framebuffer device (for graphics output)
551      <li>a simple disk controller
552      <li>a simple ethernet controller
553      <li>a real-time clock device
554  </ul>  </ul>
555    
556  <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  
557  wish to target any specific real-world machine type, for example for  wish to target any specific real-world machine type, for example for
558  educational purposes.  educational purposes.
559    
560  <p>  <p>You can read more about these experimental devices <a
561  You can read more about these experimental devices  href="experiments.html#expdevices">here</a>.
 <a href="experiments.html#expdevices">here</a>.  
   
   
562    
563    
564    
565    
566    
 <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="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>  
   
 </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.  
   
567    
568  </body>  </body>
569  </html>  </html>

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