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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>
3  </head>  <body bgcolor="#f8f8f8" text="#000000" link="#4040f0" vlink="#404040" alink="#ff0000">
4  <body bgcolor="#ffffff" text="#000000" link="#4040f0" vlink="#404040" alink="#ff0000">  <table border=0 width=100% bgcolor="#d0d0d0"><tr>
5  <p>  <td width=100% align=center valign=center><table border=0 width=100%><tr>
6  <table width="100%">  <td align="left" valign=center bgcolor="#d0efff"><font color="#6060e0" size="6">
7    <tr><td width="100%" bgcolor="#808070"><font color="#ffffe0" size="6">  <b>Gavare's eXperimental Emulator:</b></font><br>
8    <b>GXemul documentation: Introduction</b></font></td></tr>  <font color="#000000" size="6"><b>Introduction</b>
9  </table>  </font></td></tr></table></td></tr></table><p>
 <p>  
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10    
11  <!--  <!--
12    
13  $Id: intro.html,v 1.30 2005/04/07 15:43:15 debug Exp $  $Id: intro.html,v 1.100 2006/11/04 06:40:20 debug Exp $
14    
15  Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.  Copyright (C) 2003-2006  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="#cpus">Which CPU types does GXemul emulate?</a>    <li><a href="#run">How to run the emulator</a>
54      <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 66  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.
   
 <p>  
 It is important to keep in mind that devices and CPUs are not really  
 emulated correctly, they are only "faked" well enough to make eg. NetBSD  
 run. Still, the emulator could be of interest for academic research and  
 experiments, such as when learning how to write an OS for a real machine,  
 or profiling SMP, memory, or system call usage.  
   
 <p>  
 The emulator is written in C, does not depend on external libraries (except  
 X11, but that is optional), and should compile and run on most Unix-like  
 systems. If it doesn't, then that is a bug.  
75    
76  <p>  <p>Devices and processors are not simulated with 100% accuracy. They are
77  The emulator contains code which tries to emulate the workings of CPUs and  only ``faked'' well enough to allow guest operating systems to run without
78  surrounding hardware found in real machines, but it does not contain any  complaining too much. Still, the emulator could be of interest for
79  ROM code. You will need some form of program (in binary form) to run in  academic research and experiments, such as when learning how to write
80  the emulator. For many emulation modes, PROM calls are handled by the  operating system code.
81    
82    <p>The emulator is written in C, does not depend on third-party libraries,
83    and should compile and run on most 64-bit and 32-bit Unix-like systems.
84    
85    <p>The emulator contains code which tries to emulate the workings of CPUs
86    and surrounding hardware found in real machines, but it does not contain
87    any ROM code. You will need some form of program (in binary form) to run
88    in 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).
95  ECOFF, SREC, raw binaries).  
96    <p>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
98    image. (This works for example with DECstation emulation, or when booting
99    from ISO9660 CDROM images.)
100    
101    <p>Thanks to (in no specific order) Joachim Buss, Olivier Houchard, Juli
102    Mallett, Juan Romero Pardines, Alec Voropay, Göran Weinholt, Alexander
103    Yurchenko, and everyone else who has provided me with feedback.
104    
105    
 <p>  
 (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.)  
106    
107    
108    
# Line 111  For simply building and using the emulat Line 110  For simply building and using the emulat
110    
111  <p><br>  <p><br>
112  <a name="free"></a>  <a name="free"></a>
113  <h3>Is GXemul free software?</h3>  <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 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. 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.  
114    
115  <p>  Yes. I have released GXemul under a Free license. The code in GXemul is
116  (The licenses usually require that the original Copyright and license  Copyrighted software, it is <i>not</i> public domain. (If this is
117  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
118  out" if you plan to redistribute code from GXemul is to simply supply  four freedoms associated with Free software, <a
119  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>.)
120    
121    <p>The code I have written is released under a 3-clause BSD-style license
122    (or "revised BSD-style" if one wants to use <a
123    href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>). Apart from
124    the code I have written, some files are copied from other sources such as
125    NetBSD, for example header files containing symbolic names of bitfields in
126    device registers. They are also covered by similar licenses, but with some
127    additional clauses. The main point, however, is that the licenses require
128    that the original Copyright and license terms are included when you make a
129    copy or modification.
130    
131    <p>If you plan to redistribute GXemul <i>without</i> supplying the source
132    code, then you need to comply with each individual source file some other
133    way, for example by writing additional documentation containing copyright
134    notes. I have not done this, since I do not plan on making distributions
135    without source code. You need to check all individual files for details.
136    The "easiest way out" if you plan to redistribute code from GXemul is, of
137    course, to let it remain open source and simply supply the source code.
138    
139    <p>In case you want to reuse parts of GXemul, but you need to do that
140    under a different license (e.g. the GPL), then contact me and I might
141    re-license/dual-license files on a case-by-case basis.
142    
143    
144    
# Line 149  Uncompress the .tar.gz distribution file Line 154  Uncompress the .tar.gz distribution file
154          $ <b>make</b>          $ <b>make</b>
155  </pre>  </pre>
156    
157  <p>  <p>This should work on most Unix-like systems. GXemul does not require any
158  This should work on most Unix-like systems. If it doesn't, then please  specific libraries to build, however, if you build on a system which does
159  mail me a bug report.  not have X11 libraries installed, some functionality will be lost.
160    
161  <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  
162  and on compiler settings, so you might want to experiment with different  and on compiler settings, so you might want to experiment with different
163  CC and CFLAGS environment variable values. For example, on a modern PC,  CC and CFLAGS environment variable values. For example, on an AMD Athlon
164  you could try the following:  host, you might want to try setting <tt>CFLAGS</tt> to <tt>-march=athlon</tt>
165  <p>  before running <tt>configure</tt>.
166  <pre>  
167          $ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b>  
168          $ <b>make</b>  
169  </pre>  
170    
171    
172    
173    <p><br>
174    <a name="run"></a>
175    <h3>How to run the emulator:</h3>
176    
177    Once you have built GXemul, running it should be rather straight-forward.
178    Running <tt><b>gxemul</b></tt> without arguments (or with the
179    <b><tt>-h</tt></b> or <b><tt>-H</tt></b> command line options) will
180    display a help message.
181    
182  <p>  <p>
183  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
184  possible options differ between different releases and snapshots.)  read the section about <a href="guestoses.html">installing "guest"
185    operating systems</a>. If you are interested in using the emulator to
186    develop code on your own, then you should also read the section about
187    <a href="experiments.html#hello">Hello World</a>.
188    
189  <p>  <p>
 Once you have built GXemul, running it should be rather straight-forward.  
190  To exit the emulator, type CTRL-C to enter the  To exit the emulator, type CTRL-C to enter the
191  single-step debugger, and then type <b>quit</b>. By typing CTRL-B instead,  single-step debugger, and then type <tt><b>quit</b></tt>.
 a CTRL-C is sent to the emulated program.  
192    
193    <p>
194    If you are starting an emulation by entering settings directly on the
195    command line, and you are not using the <tt><b>-x</b></tt> option, then all
196    terminal input and output will go to the main controlling terminal.
197    CTRL-C is used to break into the debugger, so in order to send CTRL-C to
198    the running (emulated) program, you may use CTRL-B.
199    (This should be a reasonable compromise to allow the emulator to be usable
200    even on systems without X Windows.)
201    
202    <p>
203    There is no way to send an actual CTRL-B to the emulated program, when
204    typing in the main controlling terminal window. The solution is to either
205    use <a href="configfiles.html">configuration files</a>, or use
206    <tt><b>-x</b></tt>. Both these solutions cause new xterms to be opened for
207    each emulated serial port that is written to. CTRL-B and CTRL-C both have
208    their original meaning in those xterm windows.
209    
210    
211    
# Line 185  a CTRL-C is sent to the emulated program Line 213  a CTRL-C is sent to the emulated program
213    
214  <p><br>  <p><br>
215  <a name="cpus"></a>  <a name="cpus"></a>
216  <h3>Which CPU types does GXemul emulate?</h3>  <h3>Which processor architectures does GXemul emulate?</h3>
217    
218    The architectures that are emulated well enough to let at least one
219    guest operating system run (per architecture) are ARM, MIPS, PowerPC,
220    and SuperH.
221    
222    
223    
 <h4>MIPS:</h4>  
224    
 Emulation of R4000, which is a 64-bit CPU, was my initial goal. Right  
 now, R2000/R3000-like CPUs are also emulated (32-bit), and emulation of  
 R1x000 (at least the parts that are similar to R4000) is beginning to work  
 as expected. Code targeted for MIPS32 and MIPS64 also often work.  
225    
226  <p>  
227  I have written an experimental dynamic binary translation subsystem.  <p><br>
228  This gives higher total performance than interpreting one instruction at a  <a name="hosts"></a>
229  time and executing it. (If you wish to enable bintrans, add <b>-b</b> to  <h3>Which host architectures are supported?</h3>
230  the command line, but keep in mind that it is still experimental.)  
231    GXemul should compile and run on any modern host architecture (64-bit or
232    32-bit word-length).
233    
234    <p>(The dynamic translation engine translates into an intermediate
235    representation, but not currently into native code. This means that there
236    is no need for per-host architecture backend code.)
237    
238    
239    
240    
 <h4>URISC:</h4>  
241    
242  I have implemented an <a href="http://en.wikipedia.org/wiki/URISC">URISC</a>  <p><br>
243  emulation mode, just for fun. The only instruction available in an URISC  <a name="translation"></a>
244  machine is "reverse subtract and skip on borrow". (It is probably not  <h3>What kind of translation does GXemul use?</h3>
 worth trying to do bintrans with URISC, because any reasonable URISC  
 program relies on self-modifying code, which is bad for bintrans  
 performance.)  
245    
246    <b>Static vs. dynamic:</b>
247    
248    <p>In order to support guest operating systems, which can overwrite old
249    code pages in memory with new code, it is necessary to translate code
250    dynamically. It is not possible to do a "one-pass" (static) translation.
251    Self-modifying code and Just-in-Time compilers running inside
252    the emulator are other things that would not work with a static
253    translator. GXemul is a dynamic translator. However, it does not
254    necessarily translate into native code, like many other emulators.
255    
256    <p><b>"Runnable" Intermediate Representation:</b>
257    
258    <p>Dynamic translators usually translate from the emulated architecture
259    (e.g. MIPS) into a kind of <i>intermediate representation</i> (IR), and then
260    to native code (e.g. AMD64 or x86 code). Since one of my main goals for
261    GXemul is to keep everything as portable as possible, I have tried to make
262    sure that the IR is something which can be executed regardless of whether
263    the final step (translation from IR to native code) has been implemented
264    or not.
265    
266    <p>The IR in GXemul consists of arrays of pointers to functions, and a few
267    arguments which are passed along to those functions. The functions are
268    implemented in either manually hand-coded C, or automatically generated C.
269    In any case, this is all statically linked into the GXemul binary at link
270    time.
271    
272    <p>Here is a simplified diagram of how these arrays work.
273    
274    <p><center><img src="simplified_dyntrans.png"></center>
275    
276    <p>There is one instruction call slot for every possible program counter
277    location. In the MIPS case, instruction words are 32 bits in length,
278    and pages are (usually) 4 KB large, resulting in 1024 instruction call
279    slots. After the last of these instruction calls, there is an additional
280    call to a special "end of page" function (which doesn't count as an executed
281    instruction). This function switches to the first instruction
282    on the next virtual page (which might cause exceptions, etc).
283    
284    <p>The complexity of individual instructions vary. A simple example of
285    what an instruction can look like is the MIPS <tt>addiu</tt> instruction:
286    <pre>
287            X(addiu)
288            {
289                    reg(ic->arg[1]) = (int32_t)
290                        ((int32_t)reg(ic->arg[0]) + (int32_t)ic->arg[2]);
291            }
292    </pre>
293    
294    <p>It stores the result of a 32-bit addition of the register at arg[0]
295    with the immediate value arg[2] (treating both as signed 32-bit
296    integers) into register arg[1]. If the emulated CPU is a 64-bit CPU,
297    then this will store a correctly sign-extended value into arg[1].
298    If it is a 32-bit CPU, then only the lowest 32 bits will be stored,
299    and the high part ignored. <tt>X(addiu)</tt> is expanded to
300    <tt>mips_instr_addiu</tt> in the 64-bit case, and <tt>mips32_instr_addiu</tt>
301    in the 32-bit case. Both are compiled into the GXemul executable; no code
302    is created during run-time.
303    
304    <p>Here are examples of what the <tt>addiu</tt> instruction actually
305    looks like when it is compiled, on various host architectures:
306    
307    <p><center><table border="0">
308        <tr><td><b>GCC 4.0.1 on Alpha:</b></td>
309            <td width="35"></td><td></td>
310        <tr>
311            <td valign="top">
312    <pre>mips_instr_addiu:
313         ldq     t1,8(a1)
314         ldq     t2,24(a1)
315         ldq     t3,16(a1)
316         ldq     t0,0(t1)
317         addl    t0,t2,t0
318         stq     t0,0(t3)
319         ret</pre>
320            </td>
321            <td></td>
322            <td valign="top">
323    <pre>mips32_instr_addiu:
324         ldq     t2,8(a1)
325         ldq     t0,24(a1)
326         ldq     t3,16(a1)
327         ldl     t1,0(t2)
328         addq    t0,t1,t0
329         stl     t0,0(t3)
330         ret</pre>
331            </td>
332        </tr>
333    
334        <tr><td><b><br>GCC 3.4.4 on AMD64:</b></td>
335        <tr>
336            <td valign="top">
337    <pre>mips_instr_addiu:
338         mov    0x8(%rsi),%rdx
339         mov    0x18(%rsi),%rax
340         mov    0x10(%rsi),%rcx
341         add    (%rdx),%eax
342         cltq
343         mov    %rax,(%rcx)
344         retq</pre>
345            </td>
346            <td></td>
347            <td valign="top">
348    <pre>mips32_instr_addiu:
349         mov    0x8(%rsi),%rcx
350         mov    0x10(%rsi),%rdx
351         mov    (%rcx),%eax
352         add    0x18(%rsi),%eax
353         mov    %eax,(%rdx)
354         retq</pre>
355            </td>
356        </tr>
357    
358        <tr><td><b><br>GCC 4.0.1 on i386:</b></td>
359        <tr>
360            <td valign="top">
361    <pre>mips_instr_addiu:
362         mov    0x8(%esp),%eax
363         mov    0x8(%eax),%ecx
364         mov    0x4(%eax),%edx
365         mov    0xc(%eax),%eax
366         add    (%edx),%eax
367         mov    %eax,(%ecx)
368         cltd
369         mov    %edx,0x4(%ecx)
370         ret</pre>
371            </td>
372            <td></td>
373            <td valign="top">
374    <pre>mips32_instr_addiu:
375         mov    0x8(%esp),%eax
376         mov    0x8(%eax),%ecx
377         mov    0x4(%eax),%edx
378         mov    0xc(%eax),%eax
379         add    (%edx),%eax
380         mov    %eax,(%ecx)
381         ret</pre>
382            </td>
383        </tr>
384    </table></center>
385    
386    <p>On 64-bit hosts, there is not much difference, but on 32-bit hosts (and
387    to some extent on AMD64), the difference is enough to make it worthwhile.
388    
389    
390    <p><b>Performance:</b>
391    
392    <p>The performance of using this kind of runnable IR is obviously lower
393    than what can be achieved by emulators using native code generation, but
394    can be significantly higher than using a naive fetch-decode-execute
395    interpretation loop. In my opinion, using a runnable IR is an interesting
396    compromise.
397    
398    <p>The overhead per emulated instruction is usually around or below
399    approximately 10 host instructions. This is very much dependent on your
400    host architecture and what compiler and compiler switches you are using.
401    Added to this instruction count is (of course) also the C code used to
402    implement each specific instruction.
403    
404    <p><b>Instruction Combinations:</b>
405    
406    <p>Short, common instruction sequences can sometimes be replaced by a
407    "compound" instruction. An example could be a compare instruction followed
408    by a conditional branch instruction. The advantages of instruction
409    combinations are that
410    <ul>
411      <li>the amortized overhead per instruction is slightly reduced, and
412      <p>
413      <li>the host's compiler can make a good job at optimizing the common
414            instruction sequence.
415    </ul>
416    
417  <h4>Other CPU types:</h4>  <p>The special cases where instruction combinations give the most gain
418    are in the cores of string/memory manipulation functions such as
419    <tt>memset()</tt> or <tt>strlen()</tt>. The core loop can then (at least
420    to some extent) be replaced by a native call to the equivalent function.
421    
422    <p>The implementations of compound instructions still keep track of the
423    number of executed instructions, etc. When single-stepping, these
424    translations are invalidated, and replaced by normal instruction calls
425    (one per emulated instruction).
426    
427    <p><b>Native Code Back-ends: (not in this release)</b>
428    
429    <p>In theory, it will be possible to implement native code generation
430    (similar to what is used in high-performance emulators such as QEMU),
431    as long as that generated code abides to the C ABI on the host, but
432    for now I wanted to make sure that GXemul works without such native
433    code back-ends. For this reason, since release 0.4.0, GXemul is
434    completely free of native code back-ends.
435    
 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.)  
436    
437    
438    
# Line 228  are some other CPU modes too, but they a Line 442  are some other CPU modes too, but they a
442  <a name="accuracy"></a>  <a name="accuracy"></a>
443  <h3>Emulation accuracy:</h3>  <h3>Emulation accuracy:</h3>
444    
445  GXemul is an instruction-level simulator; things that would happen in  GXemul is an instruction-level emulator; things that would happen in
446  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
447  stages or out-of-order execution). Still, instruction-level accuracy seems  stalls or out-of-order execution). Still, instruction-level accuracy seems
448  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
449  emulator.  emulator.
450    
451    <p>The existance of instruction and data caches is "faked" to let
452    operating systems think that they are there, but for all practical
453    purposes, these caches are non-working.
454    
455    <p>The emulator is in general <i>not</i> timing-accurate, neither at the
456    instruction level nor on any higher level. An attempt is made to let
457    emulated clocks run at the same speed as the host (i.e. an emulated timer
458    running at 100 Hz will interrupt around 100 times per real second), but
459    since the host speed may vary, e.g. because of other running processes,
460    there is no guarantee as to how many instructions will be executed in
461    each of these 100 Hz cycles.
462    
463    <p>If the host is very slow, the emulated clocks might even lag behind
464    the real-world clock.
465    
466    
467    
468    
469    
# Line 242  emulator. Line 472  emulator.
472  <a name="emulmodes"></a>  <a name="emulmodes"></a>
473  <h3>Which machines does GXemul emulate?</h3>  <h3>Which machines does GXemul emulate?</h3>
474    
475  A few different machine types are emulated. The machine types that are  A few different machine types are emulated. The following machine types
476  emulated best at the moment are:  are emulated well enough to run at least one "guest OS":
477    
478  <p>  <p>
479  <ul>  <ul>
480    <li><b>DECstation 5000/200</b>&nbsp;&nbsp;("pmax")    <li><b><u>ARM</u></b>
481          <br>(Serial controller (including keyboard and mouse), ethernet,    <ul>
482          SCSI, and graphical framebuffers.)      <li><b>CATS</b> (<a href="guestoses.html#netbsdcatsinstall">NetBSD/cats</a>,
483            <a href="guestoses.html#openbsdcatsinstall">OpenBSD/cats</a>)
484        <li><b>IQ80321</b> (<a href="guestoses.html#netbsdevbarminstall">NetBSD/evbarm</a>)
485        <li><b>NetWinder</b> (<a href="guestoses.html#netbsdnetwinderinstall">NetBSD/netwinder</a>)
486      </ul>
487    <p>    <p>
488    <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)    <li><b><u>MIPS</u></b>
489          <br>(Serial controller, "VGA" text console, and SCSI.)    <ul>
490        <li><b>DECstation 5000/200</b> (<a href="guestoses.html#netbsdpmaxinstall">NetBSD/pmax</a>,
491            <a href="guestoses.html#openbsdpmaxinstall">OpenBSD/pmax</a>,
492            <a href="guestoses.html#ultrixinstall">Ultrix</a>,
493            <a href="guestoses.html#declinux">Linux/DECstation</a>,
494            <a href="guestoses.html#sprite">Sprite</a>)
495        <li><b>Acer Pica-61</b> (<a href="guestoses.html#netbsdarcinstall">NetBSD/arc</a>)
496        <li><b>NEC MobilePro 770, 780, 800, 880</b> (<a href="guestoses.html#netbsdhpcmipsinstall">NetBSD/hpcmips</a>)
497        <li><b>Cobalt</b> (<a href="guestoses.html#netbsdcobaltinstall">NetBSD/cobalt</a>)
498        <li><b>Malta</b> (<a href="guestoses.html#netbsdevbmipsinstall">NetBSD/evbmips</a>)
499        <li><b>Algorithmics P5064</b> (<a href="guestoses.html#netbsdalgorinstall">NetBSD/algor</a>)
500        <li><b>SGI O2 (aka IP32)</b> <font color="#0000e0">(<super>*1</super>)</font>
501            (<a href="guestoses.html#netbsdsgimips">NetBSD/sgi</a>)
502      </ul>
503    <p>    <p>
504    <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)    <li><b><u>PowerPC</u></b>
505          <br>(Framebuffer, keyboard, and a PCMCIA IDE controller.)    <ul>
506        <li><b>IBM 6050/6070 (PReP, PowerPC Reference Platform)</b> (<a href="guestoses.html#netbsdprepinstall">NetBSD/prep</a>)
507      </ul>
508      <p>
509      <li><b><u>SuperH</u></b>
510      <ul>
511        <li><b>Sega Dreamcast</b>
512            <font color="#0000e0">(<super>*2</super>)</font>
513            (<a href="guestoses.html#netbsddreamcast">NetBSD/dreamcast</a>)
514      </ul>
515  </ul>  </ul>
516    
517  <p>  <p>
518  There is code in GXemul for emulation of many other machine types;  <small><font color="#0000e0">(<super>*1</super>)</font> =
519  the degree to which these work range from "almost" being able to run  Enough for root-on-nfs, but not for disk boot.</small>
520  a complete OS, to almost completely unsupported (perhaps just enough  <br><small><font color="#0000e0">(<super>*2</super>)</font> =
521  support to output a few boot messages via serial console).  Only enough to reach ramdisk userland; no root-on-nfs yet.</small>
522    
523  <p>  <p>There is code in GXemul for emulation of many other machine types; the
524  In addition to specific machine types, a "test-machine" can be emulated.  degree to which these work range from almost being able to run a complete
525  A test-machine consists of one or more CPUs and a few experimental  OS, to almost completely unsupported (perhaps just enough support to
526  devices such as:  output a few boot messages via serial console).
527    
528    <p>In addition to emulating real machines, there is also a "test-machine".
529    A test-machine consists of one or more CPUs and a few experimental devices
530    such as:
531    
532  <p>  <p>
533  <ul>  <ul>
534    <li>a console I/O device (putchar() and getchar()...)    <li>a console I/O device (putchar() and getchar()...)
535    <li>an inter-processor communication device, for SMP experiments    <li>an inter-processor communication device, for SMP experiments
536    <li>a very simple linear framebuffer device (for graphics output)    <li>a very simple linear framebuffer device (for graphics output)
537      <li>a simple disk controller
538      <li>a simple ethernet controller
539      <li>a real-time clock device
540  </ul>  </ul>
541    
542  <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  
543  wish to target any specific real-world machine type, for example for  wish to target any specific real-world machine type, for example for
544  educational purposes.  educational purposes.
545    
546  <p>  <p>You can read more about these experimental devices <a
547  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 sums up 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><br>  
  <center>  
   <table border="0">  
     <tr><td>  
       <table border="0">  
         <tr><td align="center">  
           <table border="0">  
             <tr>  
               <td valign="top"><b><u>Guest&nbsp;OS:</u></b></td>  
               <td width="15">&nbsp;</td>  
               <td valign="top"><b><u>Emulation&nbsp;mode:</u></b></td>  
               <td width="35">&nbsp;</td>  
               <td valign="top"><b><u>Guest&nbsp;OS:</u></b></td>  
               <td width="15">&nbsp;</td>  
               <td valign="top"><b><u>Emulation&nbsp;mode:</u></b></td>  
             </tr>  
   
             <tr>  
               <td height="1"></td>  
             </tr>  
   
             <tr>  
               <td valign="top"><a href="http://www.netbsd.org/Ports/pmax/">NetBSD/pmax</a></td>  
               <td></td>  
               <td valign="top">DECstation</td>  
               <td></td>  
               <td valign="top"><a href="http://www.netbsd.org/Ports/arc/">NetBSD/arc</a></td>  
               <td></td>  
               <td valign="top">ARC&nbsp;(Acer&nbsp;Pica)</td>  
             </tr>  
   
             <tr>  
               <td valign="top"><a href="http://www.openbsd.org/pmax.html">OpenBSD/pmax</a></td>  
               <td></td>  
               <td valign="top">DECstation</td>  
               <td></td>  
               <td valign="top"><a href="http://www.openbsd.org/arc.html">OpenBSD/arc</a></td>  
               <td></td>  
               <td valign="top">ARC (Acer Pica)</td>  
             </tr>  
   
             <tr>  
               <td valign="top">Ultrix/RISC</td>  
               <td></td>  
               <td valign="top">DECstation</td>  
               <td></td>  
               <td valign="top"><a href="http://www.cs.berkeley.edu/projects/sprite/retrospective.html">Sprite</a></td>  
               <td></td>  
               <td valign="top">DECstation</td>  
             </tr>  
   
             <tr>  
               <td valign="top">Redhat&nbsp;Linux<super>*</super></td>  
               <td></td>  
               <td valign="top">DECstation</td>  
               <td></td>  
               <td valign="top"><a href="http://www.debian.org/">Debian&nbsp;GNU/Linux</a><super>*</super></td>  
               <td></td>  
               <td valign="top">DECstation</td>  
             </tr>  
   
             <tr>  
               <td valign="top"><a href="http://www.netbsd.org/Ports/hpcmips/">NetBSD/hpcmips</a></td>  
               <td></td>  
               <td valign="top">NEC MobilePro</td>  
             </tr>  
           </table>  
         </td></tr>  
   
         <tr><td height="15">&nbsp;</td></tr>  
   
         <tr><td>  
           <center>  
             <table border="0">  
               <tr>  
                 <td width=160 align=center><a href="netbsd-pmax-20040630.png"><img src="netbsd-pmax-20040630_small.png"></a></td>  
                 <td width=160 align=center><a href="openbsd-pmax-20040710.png"><img src="openbsd-pmax-20040710_small.png"></a></td>  
                 <td width=160 align=center><a href="ultrix4.5-20040706.png"><img src="ultrix4.5-20040706_small.gif"></a></td>  
               </tr>  
               <tr>  
                 <td align=center>NetBSD/pmax&nbsp;1.6.2</td>  
                 <td align=center>OpenBSD/pmax&nbsp;2.8</td>  
                 <td align=center>Ultrix&nbsp;4.5</td>  
               </tr>  
               <tr>  
                 <td height=10>&nbsp;</td>  
               </tr>  
               <tr>  
                 <td width=160 align=center><a href="20041024-netbsd-arc-installed.gif"><img src="20041024-netbsd-arc-installed_small.gif"></a></td>  
                 <td width=160 align=center><a href="20041024-openbsd-arc-installed.gif"><img src="20041024-openbsd-arc-installed_small.gif"></a></td>  
                 <td width=160 align=center><a href="sprite-20040711.png"><img src="sprite-20040711_small.png"></a></td>  
               </tr>  
               <tr>  
                 <td align=center>NetBSD/arc&nbsp;1.6.2</td>  
                 <td align=center>OpenBSD/arc&nbsp;2.3</td>  
                 <td align=center>Sprite</td>  
               </tr>  
               <tr>  
                 <td height=10>&nbsp;</td>  
               </tr>  
               <tr>  
                 <td width=160 align=center><a href="20041129-redhat_mips.png"><img src="20041129-redhat_mips_small.png"></a></td>  
                 <td width=160 align=center><a href="20041213-debian_4.png"><img src="20041213-debian_4_small.gif"></a></td>  
                 <td width=160 align=center><a href="20050331-netbsd-hpcmips.png"><img src="20050331-netbsd-hpcmips_small.png"></a></td>  
               </tr>  
               <tr>  
                 <td align=center>Redhat&nbsp;Linux<super>*</super></td>  
                 <td align=center>Debian&nbsp;GNU/Linux<super>*</super></td>  
                 <td align=center>NetBSD/hpcmips</td>  
               </tr>  
             </table>  
           </center>  
         </td></tr>  
       </table>  
     </td></tr>  
   </table>  
  </center>  
   
 <p><br>  
   
 (<super>*</super> Although Linux runs under DECstation emulation, the  
 default 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.)  
   
   
 <p>  
 It is non-trivial to get a specific operating system or OS kernel to  
 run in the emulator, so don't expect the list above to grow too quickly.  
   
 <p>  
 There is no guarantee that anything specific will run in the emulator, but  
 NetBSD is a good starting point for someone who wants to experiment.  
548    
549    
550    
551    
552    
 </p>  
553    
554  </body>  </body>
555  </html>  </html>

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