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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">
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>
10    
11  <!--  <!--
12    
13  $Id: intro.html,v 1.53 2005/06/26 08:42:26 debug Exp $  $Id: intro.html,v 1.66 2005/11/23 22:03:24 debug Exp $
14    
15  Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.  Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.
16    
# Line 66  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 an experimental instruction-level machine emulator. It can be  GXemul is an experimental instruction-level machine emulator. Several
68  used to run binary code for (among others) MIPS-based machines, regardless  emulation modes are available. In some modes, processors and surrounding
69  of host platform. Several emulation modes are available. For some modes,  hardware components are emulated well enough to let unmodified operating
70  processors and surrounding hardware components are emulated well enough to  systems (e.g. NetBSD) run as if they were running on a real machine.
71  let unmodified operating systems run as if they were running on a real  
72  machine.  <p>The processor architecture best emulated by GXemul is MIPS, but other
73    architectures such as ARM and PowerPC are also partially emulated.
74    
75  <p>Devices and CPUs are not simulated with 100% accuracy. They are only  <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  ``faked'' well enough to allow guest operating systems 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>The emulator is written in C, does not depend on external libraries  <p>The emulator is written in C, does not depend on third-party libraries
82  (except X11, but that is optional), and should compile and run on most  (except X11, but that is optional), and should compile and run on most
83  Unix-like systems. If it doesn't, then that is a bug. (You do not need any  Unix-like systems.
 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>The emulator contains code which tries to emulate the workings of CPUs  <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  and surrounding hardware found in real machines, but it does not contain
# Line 119  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 150  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 an AMD Athlon
163  you could try the following:  host, you might want to try setting <tt>CFLAGS</tt> to <tt>-march=athlon
164  <p>  -O3</tt> before running <tt>configure</tt>.
 <pre>  
         $ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b>  
         $ <b>make</b>  
 </pre>  
165    
 <p>  
 Run <b><tt>./configure --help</tt></b> to get a list of configure options. (The  
 possible options differ between different releases and snapshots.)  
166    
167    
168    
# Line 228  their original meaning in those xterm wi Line 219  their original meaning in those xterm wi
219  Emulation of R4000, which is a 64-bit CPU, was my initial goal.  Emulation of R4000, which is a 64-bit CPU, was my initial goal.
220  R2000/R3000-like CPUs (32-bit), R1x000, and generic MIPS32/MIPS64-style  R2000/R3000-like CPUs (32-bit), R1x000, and generic MIPS32/MIPS64-style
221  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
222  emulation.  emulation. Several guest operating systems for MIPS can run inside
223    the emulator.
 <p>  
 I have written an experimental dynamic binary translation subsystem.  
 This gives higher total performance than interpreting one instruction at a  
 time and executing it. (If you wish to enable bintrans, add <b>-b</b> to  
 the command line, but keep in mind that it is still experimental.)  
224    
225    <p>(For MIPS emulation, I have written an experimental dynamic binary
226    translation subsystem, for Alpha and i386 hosts. This gives higher total
227    performance than interpreting one instruction at a time and executing it.
228    If you wish to disable bintrans, add <b>-B</b> to the command line.)
229    
230  <h4>URISC:</h4>  <h4>ARM:</h4>
231    
232  I have implemented an <a href="http://en.wikipedia.org/wiki/URISC">URISC</a>  ARM emulation is good enough to run NetBSD/cats 2.1 and OpenBSD/cats 3.8,
233  emulation mode, just for fun. The only instruction available in an URISC  but it is not as tested or fine-tuned as the MIPS emulation mode.
 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.)  
234    
235    <h4>PowerPC:</h4>
236    
237  <h4>Other CPU types:</h4>  PowerPC emulation is still in its beginning stages, but good enough
238    to run NetBSD/prep 2.1.
 Some other CPU architectures can also be partially emulated. These are not  
 working well enough yet to run guest operating systems.  
239    
240    <p>Non-MIPS emulation modes use dynamic translation, but not recompilation
241    into native code. This makes it possible to run on any host platform.
242    
243    
244    
# Line 267  stalls or out-of-order execution). Still Line 254  stalls or out-of-order execution). Still
254  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
255  emulator.  emulator.
256    
257  <p>  <p>Caches are by default not emulated. In some cases, the existance of
258  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.
259  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
260  some old code for R2000/R3000 caches, but it has probably suffered from  suffered from bitrot by now.)
261  bitrot by now.)  
262    <p>The emulator is <i>not</i> timing-accurate. It can be run in a
263    "deterministic" mode, <tt><b>-D</b></tt>. The meaning of deterministic is
264    simply that running two emulations with the same settings will result in
265    identical runs. Obviously, this requires that no user interaction is
266    taking place, and that clock speeds are fixed with the <tt><b>-I</b></tt>
267    option. (Deterministic in this case does <i>not</i> mean that the
268    emulation will be identical to some actual real-world machine.)
269    
270    <p><font color="#ff0000">(Oops/TODO: User interaction means <i>both</i>
271    input to the emulated program/OS, and interacting with the emulator
272    itself. Breaking into the debugger and then continuing execution may
273    affect when/how interrupts occur.)</font>
274    
 <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.)  
275    
276    
277    
# Line 295  are emulated well enough to run at least Line 286  are emulated well enough to run at least
286    
287  <p>  <p>
288  <ul>  <ul>
289    <li><b>DECstation 5000/200</b>&nbsp;&nbsp;("3max")    <li><b><u>MIPS</u></b>
290          <br>Serial controller (including keyboard and mouse), ethernet,    <ul>
291          SCSI, and graphical framebuffers.      <li><b>DECstation 5000/200</b>&nbsp;&nbsp;("3max")
292    <p>      <p>
293    <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)      <li><b>Acer Pica-61</b>&nbsp;&nbsp;(an ARC machine)
294          <br>Serial controller, "VGA" text console, and SCSI.      <p>
295    <p>      <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)
296    <li><b>NEC MobilePro 770, 780, 800, and 880</b>&nbsp;&nbsp;(HPCmips machines)      <p>
297          <br>Framebuffer, keyboard, and a PCMCIA IDE controller.      <li><b>Cobalt</b>
298    <p>      <p>
299    <li><b>Cobalt</b>      <li><b>Malta</b> (evbmips)
300          <br>Serial controller and PCI IDE.      <p>
301        <li><b>SGI O2 ("IP32")</b>
302            <br><small>(Enough for root-on-nfs, but not for disk boot.)</small>
303      </ul>
304    <p>    <p>
305    <li><b>Malta (evbmips)</b>    <li><b><u>ARM</u></b>
306          <br>Serial controller and PCI IDE.    <ul>
307        <li><b>CATS</b>
308      </ul>
309    <p>    <p>
310    <li><b>SGI O2 ("IP32")</b>    <li><b><u>PowerPC</u></b>
311          <br>Serial controller and ethernet.&nbsp;&nbsp;<small>(Enough for    <ul>
312          root-on-nfs, but not for disk boot.)</small>      <li><b>PReP (PowerPC Reference Platform)</b>
313      </ul>
314  </ul>  </ul>
315    
316  <p>There is code in GXemul for emulation of many other machine types; the  <p>There is code in GXemul for emulation of many other machine types; the
# Line 330  such as: Line 327  such as:
327    <li>a console I/O device (putchar() and getchar()...)    <li>a console I/O device (putchar() and getchar()...)
328    <li>an inter-processor communication device, for SMP experiments    <li>an inter-processor communication device, for SMP experiments
329    <li>a very simple linear framebuffer device (for graphics output)    <li>a very simple linear framebuffer device (for graphics output)
330      <li>a simple SCSI disk controller
331      <li>a simple ethernet controller
332  </ul>  </ul>
333    
334  <p>This mode is useful if you wish to run experimental code, but do not  <p>This mode is useful if you wish to run experimental code, but do not
# Line 444  interacted with similar to a real machin Line 443  interacted with similar to a real machin
443            <td></td>            <td></td>
444          </tr>          </tr>
445    
446            <tr><td height="10"></td></tr>
447    
448            <tr>
449              <td></td>
450              <td align="center"><a href="20051007-netbsd-cats-installed.png"><img src="20051007-netbsd-cats-installed_small.png"></a></td>
451              <td></td>
452              <td><a href="http://www.netbsd.org/Ports/cats/">NetBSD/cats</a>
453                    <br>CATS</td>
454              <td></td>
455              <td align="center"><a href="20051007-openbsd-cats-installed.png"><img src="20051007-openbsd-cats-installed_small.png"></a></td>
456              <td></td>
457              <td><a href="http://www.openbsd.org/cats.html">OpenBSD/cats</a>
458                    <br>CATS</td>
459              <td></td>
460            </tr>
461    
462            <tr><td height="10"></td></tr>
463    
464            <tr>
465              <td></td>
466              <td align="center"><a href="20051123-netbsd-prep.png"><img src="20051123-netbsd-prep_small.png"></a></td>
467              <td></td>
468              <td><a href="http://www.netbsd.org/Ports/prep/">NetBSD/prep</a>
469                    <br>PReP</td>
470              <td></td>
471            </tr>
472    
473  </table></center>  </table></center>
474    
475    

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