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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>
 </head>  
3  <body bgcolor="#f8f8f8" text="#000000" link="#4040f0" vlink="#404040" alink="#ff0000">  <body bgcolor="#f8f8f8" text="#000000" link="#4040f0" vlink="#404040" alink="#ff0000">
4  <table border=0 width=100% bgcolor="#d0d0d0"><tr>  <table border=0 width=100% bgcolor="#d0d0d0"><tr>
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:&nbsp;&nbsp;&nbsp;</b></font>
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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10    
11  <!--  <!--
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13  $Id: intro.html,v 1.46 2005/06/04 12:02:17 debug Exp $  $Id: intro.html,v 1.64 2005/10/07 22:45:33 debug Exp $
14    
15  Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.  Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.
16    
# Line 56  SUCH DAMAGE. Line 53  SUCH DAMAGE.
53    <li><a href="#cpus">Which CPU types does GXemul emulate?</a>    <li><a href="#cpus">Which CPU types does GXemul emulate?</a>
54    <li><a href="#accuracy">Emulation accuracy</a>    <li><a href="#accuracy">Emulation accuracy</a>
55    <li><a href="#emulmodes">Which machines does GXemul emulate?</a>    <li><a href="#emulmodes">Which machines does GXemul emulate?</a>
56    <li><a href="#guestos">Which guest OSes are possible to run?</a>    <li><a href="#guestos">Which guest OSes are possible to run in GXemul?</a>
57  </ul>  </ul>
58    
59    
# Line 67  SUCH DAMAGE. Line 64  SUCH DAMAGE.
64  <a name="overview"></a>  <a name="overview"></a>
65  <h3>Overview:</h3>  <h3>Overview:</h3>
66    
67  GXemul is a machine emulator, which can be used to experiment with  GXemul is an experimental instruction-level machine emulator. Several
68  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  
69  hardware components are emulated well enough to let unmodified operating  hardware components are emulated well enough to let unmodified operating
70  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.
71    
72  <p>  <p>The processor architecture best emulated by GXemul is MIPS, but other
73  Devices and CPUs are not simulated with 100% accuracy. They are only  architectures are also partially emulated.
74  "faked" well enough to make operating systems (eg NetBSD) run without  
75    <p>Devices and CPUs are not simulated with 100% accuracy. They are only
76    ``faked'' well enough to make operating systems (e.g. NetBSD) run without
77  complaining too much. Still, the emulator could be of interest for  complaining too much. Still, the emulator could be of interest for
78  academic research and experiments, such as when learning how to write  academic research and experiments, such as when learning how to write
79  operating system code.  operating system code.
80    
81  <p>  <p>The emulator is written in C, does not depend on external libraries
82  The emulator is written in C, does not depend on external libraries (except  (except X11, but that is optional), and should compile and run on most
83  X11, but that is optional), and should compile and run on most Unix-like  Unix-like systems. If it doesn't, then that is a bug.
84  systems. If it doesn't, then that is a bug.  
85  (You do not need any MIPS compiler toolchain to build or use GXemul.  <p>The emulator contains code which tries to emulate the workings of CPUs
86  If you need to compile MIPS binaries from sources, then of course you need  and surrounding hardware found in real machines, but it does not contain
87  such a toolchain, but that is completely separate from GXemul.)  any ROM code. You will need some form of program (in binary form) to run
88    in the emulator. For many emulation modes, PROM calls are handled by the
 <p>  
 The emulator contains code which tries to emulate the workings of CPUs and  
 surrounding hardware found in real machines, but it does not contain any  
 ROM code. You will need some form of program (in binary form) to run in  
 the emulator. For many emulation modes, PROM calls are handled by the  
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, or when booting
99  from ISO9660 CDROM images.)  from ISO9660 CDROM images.)
# Line 112  from ISO9660 CDROM images.) Line 103  from ISO9660 CDROM images.)
103    
104    
105    
106    
107    
108  <p><br>  <p><br>
109  <a name="free"></a>  <a name="free"></a>
110  <h3>Is GXemul Free software?</h3>  <h3>Is GXemul Free software?</h3>
# Line 122  confusing to you, you might want to read Line 115  confusing to you, you might want to read
115  four freedoms associated with Free software, <a  four freedoms associated with Free software, <a
116  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>.)
117    
118  <p>  <p>The code I have written is released under a 3-clause BSD-style license
119  The code I have written is released under a 3-clause BSD-style license  (or "revised BSD-style" if one wants to use <a
120  (or "revised BSD-style" if one wants to use  href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>). Apart from
121  <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
122  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
123  such as NetBSD, for example header files containing symbolic names of  device registers. They are also covered by similar licenses, but with some
124  bitfields in device registers. They are also covered by similar licenses,  additional clauses. The main point, however, is that the licenses require
125  but with some additional clauses. If you plan to redistribute GXemul  that the original Copyright and license terms are included when you make a
126  (for example as a binary package), or reuse code from GXemul,  copy or modification.
127  then you should check those files for their license terms.  
128    <p>If you plan to redistribute GXemul <i>without</i> supplying the source
129    code, then you need to comply with each individual source file some other
130    way, for example by writing additional documentation containing copyright
131    notes. I have not done this, since I do not plan on making distributions
132    without source code. You need to check all individual files for details.
133    The "easiest way out" if you plan to redistribute code from GXemul is, of
134    course, to let it remain open source and simply supply the source code.
135    
136    <p>(If a stable, unmodified release of GXemul is packaged into binary form,
137    and it is clear which version of GXemul was used to build the package,
138    then it can be argued that the source code is available, just not in that
139    specific package. Common sense should be used in this case, and not
140    pedanticism.)
141    
 <p>  
 (The licenses usually require that the original Copyright and license  
 terms are included when you make a copy or modification. The "easiest way  
 out" if you plan to redistribute code from GXemul is to simply supply  
 the source code. You should however check individual files for details.)  
142    
143    
144    
# Line 153  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. If it doesn't, then
 This should work on most Unix-like systems. If it doesn't, then  
158  mail me a bug report.  mail me a bug report.
159    
160  <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  
161  and on compiler settings, so you might want to experiment with different  and on compiler settings, so you might want to experiment with different
162  CC and CFLAGS environment variable values. For example, on a modern PC,  CC and CFLAGS environment variable values. For example, on a modern PC,
163  you could try the following:  you could try the following:
164  <p>  <p><pre>
165  <pre>          $ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b>
166          $ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b>          $ <b>make</b>
         $ <b>make</b>  
167  </pre>  </pre>
168    
 <p>  
 Run <b><tt>./configure --help</tt></b> to get a list of configure options. (The  
 possible options differ between different releases and snapshots.)  
169    
170    
171    
# Line 233  R2000/R3000-like CPUs (32-bit), R1x000, Line 224  R2000/R3000-like CPUs (32-bit), R1x000,
224  CPUs are also emulated, and are hopefully almost as stable as the R4000  CPUs are also emulated, and are hopefully almost as stable as the R4000
225  emulation.  emulation.
226    
227  <p>  <p>I have written an experimental dynamic binary translation subsystem.
 I have written an experimental dynamic binary translation subsystem.  
228  This gives higher total performance than interpreting one instruction at a  This gives higher total performance than interpreting one instruction at a
229  time and executing it. (If you wish to enable bintrans, add <b>-b</b> to  time and executing it. (If you wish to disable bintrans, add <b>-B</b> to
230  the command line, but keep in mind that it is still experimental.)  the command line.)
   
   
 <h4>URISC:</h4>  
   
 I have implemented an <a href="http://en.wikipedia.org/wiki/URISC">URISC</a>  
 emulation mode, just for fun. The only instruction available in an URISC  
 machine is "reverse subtract and skip on borrow". (It is probably not  
 worth trying to do bintrans with URISC, because any reasonable URISC  
 program relies on self-modifying code, which is bad for bintrans  
 performance.)  
231    
232    <h4>ARM:</h4>
233    
234  <h4>POWER/PowerPC</h4>  The ARM CPU emulation is good enough to run NetBSD/cats and OpenBSD/cats
235    (almost bugfree :-), but it is not as tested or fine-tuned as the MIPS
236  There is some code for 64-bit (and 32-bit) POWER/PowerPC emulation, enough  emulation.
 to run "Hello World", but not enough to run complete operating systems.    
 This mode isn't really working yet.  
   
237    
238  <h4>Other CPU types:</h4>  <h4>Other CPU types:</h4>
239    
240  Some other CPU architectures (such as x86) can also be partially emulated.  Some other CPU architectures can also be partially emulated. These are not
241  These are not enabled by default though, because of their unstable-ness.  working well enough yet to run guest operating systems.
242    
243    
244    
245    
# Line 276  stalls or out-of-order execution). Still Line 255  stalls or out-of-order execution). Still
255  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
256  emulator.  emulator.
257    
258  <p>  <p>Caches are by default not emulated. In some cases, the existance of
259  Caches are by default not emulated. In some cases, the existance of caches  caches is "faked" to let operating systems think that they are there.
260  is "faked" to let operating systems think that they are there. (There is  (There is some old code for R2000/R3000 caches, but it has probably
261  some old code for R2000/R3000 caches, but it has probably suffered from  suffered from bitrot by now.)
262  bitrot by now.)  
263    <p>The emulator is <i>not</i> timing-accurate. It can be run in a
264  <p>  "deterministic" mode, <tt><b>-D</b></tt>. The meaning of deterministic is
265  The emulator is <i>not</i> timing-accurate. It can be run in a  simply that running two emulations with the same settings will result in
266  "deterministic" mode, <tt><b>-D</b></tt>. The meaning of deterministic is  identical runs. Obviously, this requires that no user interaction is
267  simply that running two emulations with the same settings will result in  taking place, and that clock speeds are fixed with the <tt><b>-I</b></tt>
268  identical runs. Obviously, this requires that no user interaction is  option. (Deterministic in this case does <i>not</i> mean that the
269  taking place, and that clock speeds are fixed with the <tt><b>-I</b></tt>  emulation will be identical to some actual real-world machine.)
 option. (Deterministic in this case does <i>not</i> mean that the emulation  
 will be identical to some actual real-world machine.)  
270    
271    
272    
# Line 304  are emulated well enough to run at least Line 281  are emulated well enough to run at least
281    
282  <p>  <p>
283  <ul>  <ul>
284    <li><b>DECstation 5000/200</b>&nbsp;&nbsp;("3max")    <li><b><u>MIPS</u></b>
285      <ul>
286        <li><b>DECstation 5000/200</b>&nbsp;&nbsp;("3max")
287          <br>Serial controller (including keyboard and mouse), ethernet,          <br>Serial controller (including keyboard and mouse), ethernet,
288          SCSI, and graphical framebuffers.          SCSI, and graphical framebuffers.
289    <p>      <p>
290    <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)      <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)
291          <br>Serial controller, "VGA" text console, and SCSI.          <br>Serial controller, "VGA" text console, and SCSI.
292    <p>      <p>
293    <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)      <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)
294          <br>Framebuffer, keyboard, and a PCMCIA IDE controller.          <br>Framebuffer, keyboard, and a PCMCIA IDE controller.
295    <p>      <p>
296    <li><b>Cobalt</b>      <li><b>Cobalt</b>
297            <br>Serial controller and PCI IDE.
298        <p>
299        <li><b>Malta (evbmips)</b>
300          <br>Serial controller and PCI IDE.          <br>Serial controller and PCI IDE.
301        <p>
302        <li><b>SGI O2 ("IP32")</b>
303            <br>Serial controller and ethernet.&nbsp;&nbsp;<small>(Enough for
304            root-on-nfs, but not for disk boot.)</small>
305      </ul>
306      <p>
307      <li><b><u>ARM</u></b>
308      <ul>
309        <li><b>CATS</b>
310            <br>VGA and PCI IDE.
311      </ul>
312  </ul>  </ul>
313    
314  <p>  <p>There is code in GXemul for emulation of many other machine types; the
315  There is code in GXemul for emulation of many other machine types;  degree to which these work range from almost being able to run a complete
316  the degree to which these work range from "almost" being able to run  OS, to almost completely unsupported (perhaps just enough support to
317  a complete OS, to almost completely unsupported (perhaps just enough  output a few boot messages via serial console).
318  support to output a few boot messages via serial console).  
319    <p>In addition to emulating real machines, there is also a "test-machine".
320  <p>  A test-machine consists of one or more CPUs and a few experimental devices
321  In addition to emulating real machines, there is also a "test-machine".  such as:
 A test-machine consists of one or more CPUs and a few experimental  
 devices such as:  
322    
323  <p>  <p>
324  <ul>  <ul>
325    <li>a console I/O device (putchar() and getchar()...)    <li>a console I/O device (putchar() and getchar()...)
326    <li>an inter-processor communication device, for SMP experiments    <li>an inter-processor communication device, for SMP experiments
327    <li>a very simple linear framebuffer device (for graphics output)    <li>a very simple linear framebuffer device (for graphics output)
328      <li>a simple SCSI disk controller
329      <li>a simple ethernet controller
330  </ul>  </ul>
331    
332  <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  
333  wish to target any specific real-world machine type, for example for  wish to target any specific real-world machine type, for example for
334  educational purposes.  educational purposes.
335    
336  <p>  <p>You can read more about these experimental devices <a
337  You can read more about these experimental devices  href="experiments.html#expdevices">here</a>.
 <a href="experiments.html#expdevices">here</a>.  
338    
339    
340    
# Line 353  You can read more about these experiment Line 344  You can read more about these experiment
344    
345  <p><br>  <p><br>
346  <a name="guestos"></a>  <a name="guestos"></a>
347  <h3>Which guest OSes are possible to run?</h3>  <h3>Which guest OSes are possible to run in GXemul?</h3>
348    
349  This table lists the guest OSes that run well enough to be considered  This table lists the guest OSes that run well enough to be considered
350  working in the emulator. They can boot from a harddisk image and be  working in the emulator. They can boot from a harddisk image and be
# Line 434  interacted with similar to a real machin Line 425  interacted with similar to a real machin
425                  <br>Cobalt</td>                  <br>Cobalt</td>
426          </tr>          </tr>
427    
428            <tr><td height="10"></td></tr>
429    
430            <tr>
431              <td></td>
432              <td align="center"><a href="20050626-netbsd-sgimips-netboot.png"><img src="20050626-netbsd-sgimips-netboot_small.png"></a></td>
433              <td></td>
434              <td><a href="http://www.netbsd.org/Ports/sgimips/">NetBSD/sgimips</a>
435                    <br>SGI O2 ("IP32")</td>
436              <td></td>
437              <td align="center"><a href="20050622-netbsd-evbmips-malta.png"><img src="20050622-netbsd-evbmips-malta_small.png"></a></td>
438              <td></td>
439              <td><a href="http://www.netbsd.org/Ports/evbmips/">NetBSD/evbmips</a>
440                    <br>5Kc (and 4Kc) Malta<br>evaluation boards</td>
441              <td></td>
442            </tr>
443    
444            <tr><td height="10"></td></tr>
445    
446            <tr>
447              <td></td>
448              <td align="center"><a href="20051007-netbsd-cats-installed.png"><img src="20051007-netbsd-cats-installed_small.png"></a></td>
449              <td></td>
450              <td><a href="http://www.netbsd.org/Ports/cats/">NetBSD/cats</a>
451                    <br>CATS</td>
452              <td></td>
453              <td align="center"><a href="20051007-openbsd-cats-installed.png"><img src="20051007-openbsd-cats-installed_small.png"></a></td>
454              <td></td>
455              <td><a href="http://www.openbsd.org/cats.html">OpenBSD/cats</a>
456                    <br>CATS</td>
457              <td></td>
458            </tr>
459    
460  </table></center>  </table></center>
461    
462    

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