/[gxemul]/trunk/doc/intro.html

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-revision 4 by dpavlin,
Mon Oct  8 16:18:00 2007 UTC
+revision 8 by dpavlin,
Mon Oct  8 16:18:19 2007 UTC
 Line 1
  <html>
  <head><title>GXemul documentation: Introduction</title>
+ <meta name="robots" content="noarchive,nofollow,noindex">
  </head>
  <body bgcolor="#f8f8f8" text="#000000" link="#4040f0" vlink="#404040" alink="#ff0000">
  <table border=0 width=100% bgcolor="#d0d0d0"><tr>
-Line 8
+Line 9
  <b>GXemul documentation:</b></font>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  <font color="#000000" size="6"><b>Introduction</b>
  </font></td></tr></table></td></tr></table><p>
- <!-- The first 10 lines are cut away by the homepage updating script.  -->
  <!--
- $Id: intro.html,v 1.40 2005/04/27 15:22:17 debug Exp $
+ $Id: intro.html,v 1.47 2005/06/04 22:47:49 debug Exp $
  Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.
-Line 52 
 SUCH DAMAGE.
+Line 51 
 SUCH DAMAGE.
    <li><a href="#overview">Overview</a>
    <li><a href="#free">Is GXemul Free software?</a>
    <li><a href="#build">How to compile/build the emulator</a>
+   <li><a href="#run">How to run the emulator</a>
    <li><a href="#cpus">Which CPU types does GXemul emulate?</a>
    <li><a href="#accuracy">Emulation accuracy</a>
    <li><a href="#emulmodes">Which machines does GXemul emulate?</a>
 Line 73 
 hardware components are emulated well en
  systems run as if they were running on a real machine.
  <p>
- It is important to keep in mind that devices and CPUs are not simulated
+ Devices and CPUs are not simulated with 100% accuracy. They are only
- with 100% accuracy. They are only "faked" well enough to make operating
+ "faked" well enough to make operating systems (eg NetBSD) run without
- systems (eg NetBSD) run. Still, the emulator could be of interest for
+ complaining too much. Still, the emulator could be of interest for
  academic research and experiments, such as when learning how to write
  operating system code.
  <p>
 Line 85 
 X11, but that is optional), and should c
  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. There
+ such a toolchain, but that is completely separate from GXemul.)
- 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.)
  <p>
  The emulator contains code which tries to emulate the workings of CPUs and
-Line 101 
 emulator itself, so you do not need to u
+Line 98 
 emulator itself, so you do not need to u
  You can use pre-compiled kernels (for example NetBSD kernels, or Linux),
  or other programs that are in binary format, and in some cases even actual
  ROM images. A couple of different file formats are supported (ELF, a.out,
- ECOFF, SREC, raw binaries).
+ ECOFF, SREC, and raw binaries).
+ <p>
+ If you do not have a kernel as a separate file, but you have a bootable
+ disk image, then it is sometimes possible to boot directly from that
+ image. (This works for example with DECstation emulation, or when booting
+ from ISO9660 CDROM images.)
-Line 111 
 ECOFF, SREC, raw binaries).
+Line 115 
 ECOFF, SREC, raw binaries).
  <a name="free"></a>
  <h3>Is GXemul Free software?</h3>
- Yes. I have released GXemul under a Free license.
+ Yes. I have released GXemul under a Free license. The code in GXemul is
- (For a definitions of the four freedoms associated with Free software,
+ Copyrighted software, it is <i>not</i> public domain. (If this is
- please read <a href="http://www.gnu.org/philosophy/free-sw.html">
+ confusing to you, you might want to read up on the definitions of the
- http://www.gnu.org/philosophy/free-sw.html</a>.)
+ four freedoms associated with Free software, <a
+ href="http://www.gnu.org/philosophy/free-sw.html">http://www.gnu.org/philosophy/free-sw.html</a>.)
- <p>
- The code in GXemul is Copyrighted software, it is <i>not</i> public
- domain or anything like that.
  <p>
  The code I have written is released under a 3-clause BSD-style license
-Line 171 
 you could try the following:
+Line 172 
 you could try the following:
  </pre>
  <p>
- Run <b>./configure --help</b> to get a list of configure options. (The
+ Run <b><tt>./configure --help</tt></b> to get a list of configure options. (The
  possible options differ between different releases and snapshots.)
- <p>
+ <p><br>
+ <a name="run"></a>
+ <h3>How to run the emulator:</h3>
  Once you have built GXemul, running it should be rather straight-forward.
+ Running <tt><b>gxemul</b></tt> without arguments (or with the
+ <b><tt>-h</tt></b> or <b><tt>-H</tt></b> command line options) will
+ display a help message.
+ <p>
+ To get some ideas about what is possible to run in the emulator, please
+ read the section about <a href="guestoses.html">installing "guest"
+ operating systems</a>. If you are interested in using the emulator to
+ develop code on your own, then you should also read the section about
+ <a href="experiments.html#hello">Hello World</a>.
+ <p>
  To exit the emulator, type CTRL-C to enter the
- single-step debugger, and then type <b>quit</b>.
+ single-step debugger, and then type <tt><b>quit</b></tt>.
  <p>
  If you are starting an emulation by entering settings directly on the
- command line, and you are not using the <b>-x</b> option, then all
+ command line, and you are not using the <tt><b>-x</b></tt> option, then all
  terminal input and output will go to the main controlling terminal.
  CTRL-C is used to break into the debugger, so in order to send CTRL-C to
  the running (emulated) program, you may use CTRL-B.
+ (This should be a reasonable compromise to allow the emulator to be usable
+ even on systems without X Windows.)
  <p>
- (This is an ugly hack; there is no way to send an actual CTRL-B to the
+ There is no way to send an actual CTRL-B to the emulated program, when
- emulated program, when typing in the main controlling terminal window.
+ typing in the main controlling terminal window. The solution is to either
- The solution is to either use configuration files, or use <b>-x</b>. Both
+ use <a href="configfiles.html">configuration files</a>, or use
- these solutions cause new xterms to be opened for each emulated serial
+ <tt><b>-x</b></tt>. Both these solutions cause new xterms to be opened for
- port. CTRL-B and CTRL-C both have their original meaning in those
+ each emulated serial port that is written to. CTRL-B and CTRL-C both have
- xterm windows.)
+ their original meaning in those xterm windows.
-Line 205 
 xterm windows.)
+Line 227 
 xterm windows.)
  <h4>MIPS:</h4>
- Emulation of R4000, which is a 64-bit CPU, was my initial goal. Right
+ Emulation of R4000, which is a 64-bit CPU, was my initial goal.
- now, R2000/R3000-like CPUs are also emulated (32-bit), and emulation of
+ R2000/R3000-like CPUs (32-bit), R1x000, and generic MIPS32/MIPS64-style
- R1x000 (at least the parts that are similar to R4000) is beginning to work
+ CPUs are also emulated, and are hopefully almost as stable as the R4000
- as expected. Code targeted for MIPS32 and MIPS64 also often work.
+ emulation.
  <p>
  I have written an experimental dynamic binary translation subsystem.
-Line 217 
 time and executing it. (If you wish to e
+Line 239 
 time and executing it. (If you wish to e
  the command line, but keep in mind that it is still experimental.)
  <h4>URISC:</h4>
  I have implemented an <a href="http://en.wikipedia.org/wiki/URISC">URISC</a>
-Line 228 
 program relies on self-modifying code, w
+Line 249 
 program relies on self-modifying code, w
  performance.)
+ <h4>POWER/PowerPC</h4>
+ There is some code for 64-bit (and 32-bit) POWER/PowerPC emulation, enough
+ to run "Hello World", but not enough to run complete operating systems.
+ This mode isn't really working yet.
  <h4>Other CPU types:</h4>
- There is some code for 64-bit (and 32-bit) POWER/PowerPC emulation too,
+ Some other CPU architectures (such as x86) can also be partially emulated.
- but it only works for "Hello World" and similarly trivial programs. (There
+ These are not enabled by default though, because of their unstable-ness.
- are some other CPU modes too, but they are working even less.)
-Line 244 
 are some other CPU modes too, but they a
+Line 269 
 are some other CPU modes too, but they a
  <a name="accuracy"></a>
  <h3>Emulation accuracy:</h3>
- GXemul is an instruction-level simulator; things that would happen in
+ GXemul is an instruction-level emulator; things that would happen in
  several steps within a real CPU are not taken into account (eg. pipe-line
- stages or out-of-order execution). Still, instruction-level accuracy seems
+ stalls or out-of-order execution). Still, instruction-level accuracy seems
  to be enough to be able to run complete guest operating systems inside the
  emulator.
+ <p>
+ Caches are by default not emulated. In some cases, the existance of caches
+ is "faked" to let operating systems think that they are there. (There is
+ some old code for R2000/R3000 caches, but it has probably suffered from
+ bitrot by now.)
+ <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.)
-Line 322 
 interacted with similar to a real machin
+Line 362 
 interacted with similar to a real machin
  <center><table border="0">
          <tr>
            <td width="10"></td>
-           <td align="center"><a href="netbsd-pmax-20040630.png"><img src="netbsd-pmax-20040630_small.png"></a></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>

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