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

This is repository of my old source code which isn't updated any more. Go to git.rot13.org for current projects!

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-revision 12 by dpavlin,
Mon Oct  8 16:18:38 2007 UTC
+revision 20 by dpavlin,
Mon Oct  8 16:19:23 2007 UTC
 Line 10
  <!--
- $Id: technical.html,v 1.62 2005/08/16 05:15:24 debug Exp $
+ $Id: technical.html,v 1.67 2005/11/24 12:32:10 debug Exp $
  Copyright (C) 2004-2005  Anders Gavare.  All rights reserved.
 Line 64 
 SUCH DAMAGE.
  <a name="speed"></a>
  <h3>Speed and emulation modes</h3>
- So, how fast is GXemul? There is no good answer to this. There is
+ So, how fast is GXemul? There is no short answer to this. There is
  especially no answer to the question <b>What is the slowdown factor?</b>,
  because the host architecture and emulated architecture can usually not be
  compared just like that.
 Line 89 
 with the emulator. Typical examples woul
  install NetBSD?", or "How long does it take to compile XYZ inside NetBSD
  in the emulator?".
+ <p>So, how fast is it? :-)&nbsp;&nbsp;&nbsp;Answer: it varies.
  <p>The emulation technique used varies depending on which processor type
  is being emulated. (One of my main goals with GXemul is to experiment with
  different kinds of emulation, so these might change in the future.)
-Line 106 
 different kinds of emulation, so these m
+Line 108 
 different kinds of emulation, so these m
          line option.)
    <p>
    <li><b>All other modes:</b><br>
-         These are under development, using a new dynamic translation
+         These use a kind of dynamic translation system. (This system does
-         system. This system does not use host-specific backends.
+         not use host-specific backends, so it is not "recompilation" or
-         Speed is slower than real binary translation, but faster than
+         anything like that.) Speed is slower than real binary translation,
-         traditional interpretation, and with some tricks it will hopefully
+         but faster than traditional interpretation, and with some tricks
-         still give reasonable speed. These modes don't really work yet,
+         it will hopefully still give reasonable speed. The ARM and PowerPC
-         and are not enabled by default in the stable release.
+         emulation modes uses this kind of translation.
  </ul>
-Line 316 
 a CDROM ISO image. You can use a read-wr
+Line 318 
 a CDROM ISO image. You can use a read-wr
  files in both directions, but then you should be aware of the
  fragmentation issue mentioned above.
- <p>TODO: Write a section on how to connect multiple emulator instances.
- (Using the <tt>local_port</tt> and <tt>add_remote</tt> configuration file
- commands.)
-Line 329 
 commands.)
+Line 328 
 commands.)
  <a name="devices"></a>
  <h3>Emulation of hardware devices</h3>
- Each file in the <tt>src/device/</tt> directory is responsible for one
+ Each file called <tt>dev_*.c</tt> in the <tt>src/device/</tt> directory is
- hardware device. These are used from <tt>src/machine.c</tt>, when
+ responsible for one hardware device. These are used from
- initializing which hardware a particular machine model will be using, or
+ <tt>src/machine.c</tt>, when initializing which hardware a particular
- when adding devices to a machine using the <tt>device()</tt> command in
+ machine model will be using, or when adding devices to a machine using the
- configuration files.
+ <tt>device()</tt> command in configuration files.
- <p><font color="#ff0000">NOTE: The device registry subsystem is currently
- in a state of flux, as it is being redesigned.</font>
  <p>(I'll be using the name "<tt>foo</tt>" as the name of the device in all
  these examples.  This is pseudo code, it might need some modification to
-Line 372 
 actually compile and run.)
+Line 368 
 actually compile and run.)
                  memory_device_register(devinit->machine->memory, devinit->name,
                      devinit->addr, DEV_FOO_LENGTH,
-                     dev_foo_access, (void *)d, MEM_DEFAULT, NULL);
+                     dev_foo_access, (void *)d, DM_DEFAULT, NULL);
                  /*  This should only be here if the device
                      has a tick function:  */
-Line 392 
 actually compile and run.)
+Line 388 
 actually compile and run.)
                  /*  ...  */
          }
  </pre><br>
+         (There is an exception to this rule; ugly hacks which allow
+         code in <tt>src/machine.c</tt> to use some structures makes it
+         necessary to place the <tt>struct foo_data</tt> in
+         <tt>src/include/devices.h</tt> instead of in <tt>dev_foo.c</tt>
+         itself. This is useful for example for interrupt controllers.)
+   <p>
    <li>If <tt>foo</tt> has a tick function (that is, something that needs to be
          run at regular intervals) then <tt>FOO_TICKSHIFT</tt> and a tick
          function need to be defined as well:
  <pre>
-         #define FOO_TICKSHIFT           10
+         #define FOO_TICKSHIFT           14
          void dev_foo_tick(struct cpu *cpu, void *extra)
          {
-Line 410 
 actually compile and run.)
+Line 411 
 actually compile and run.)
          }
  </pre><br>
+   <li>Does this device belong to a standard bus?
+         <ul>
+           <li>If this device should be detectable as a PCI device, then
+                 glue code should be added to
+                 <tt>src/devices/bus_pci.c</tt>.
+           <li>If this is a legacy ISA device which should be usable by
+                 any machine which has an ISA bus, then the device should
+                 be added to <tt>src/devices/bus_isa.c</tt>.
+         </ul>
+   <p>
    <li>And last but not least, the device should have an access function.
          The access function is called whenever there is a load or store
          to an address which is in the device' memory mapped region.

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