Re: [Fwd: Latest version of CPU emulator] (fwd)

Re: [Fwd: Latest version of CPU emulator] (fwd)

[Alberto Vignani]

On Wed, 18 Aug 1999 Brad Boyer <flar@marcus.pants.nu> wrote:

>Geert Uytterhoeven wrote:
>> Perhaps Gabriel's 486SX emulator can be included as an optimization?
>
>I doubt it, from what I know of both emulators.  The one that was submitted
>for Wine is protected mode only, and Gabriel's is real mode only.  I
>imagine the ideas and some of the code from Gabriel's emulator could
>be adapted to this use, but it definitely couldn't be used without
>some major changes.  It might be a good place to start, tho.
>

dosemu (www.dosemu.org) has an x86 emulator derived from the one in Twin
(www.willows.com). I am now testing the Twin version on the iMac and the
results are already very encouraging, the emulator is quite fast and has
no endianness problems AFAIK.
However, the Twin emulator does 16-bit protected mode only. But the dosemu
version can do almost all, from real mode to 32-bit DPMI. GDT,LDT and
paging have already been implemented, even if not yet fully debugged.
The dosemu version is at http://www.dosemu.org/~alberto.

Alberto

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[Fwd: Latest version of CPU emulator] (fwd)

[Geert Uytterhoeven]

Perhaps Gabriel's 486SX emulator can be included as an optimization?

---------- Forwarded message ----------
Date: Tue, 17 Aug 1999 20:52:01 -0400
From: Jeff Garzik <jgarzik@pobox.com>
To: Geert.Uytterhoeven@cs.kuleuven.ac.be, rth@cygnus.com
Subject: [Fwd: Latest version of CPU emulator]

Geert and rth,

This is unrelated to Linux kernel but I hope you can still help.  I am
trying to drum up developer interest in WINE -- specifically the
interest of coders on non-x86 platforms.  Do you think you could perhaps
forward this message to pertinent lists?  (I am no longer on axp-list,
and am not on the m68k/ppc/etc lists)

WINE is on the verge of being able to run Win16 and Win32 programs on
non-x86 platforms.  Ulrich Weigand, a WINE hacker, has completed x86 CPU
emulation support, including full x86 instruction set through P-III and
all addressing modes.  The only thing that keeps his CPU emulator from
running WINE on the PPC today is issues that he can't test himself: 
endianness and alignment and other processor differences.

Hopefully the major work is done.  The CPU emulator has
processor-neutral code to decode and emulate each instruction from 8086
through P-III.  All that is left is a need for developers on non-x86
platforms to pick up the reins and stomp out the remaining issues.

Ulrich's latest code was just posted to wine-devel, at
http://www.integrita.com/cgi-local/lwgate.pl/WINE-DEVEL/archives/1999-08/date/article-315.html 
I looked through it, and it is very readable.

Regards,

	Jeff





-- 
Any sufficiently advanced technology is indistinguishable from a rigged
demo.
	-- Andy Finkel


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Re: [Fwd: Latest version of CPU emulator] (fwd)

[Brad Boyer]

Geert Uytterhoeven wrote:
> Perhaps Gabriel's 486SX emulator can be included as an optimization?

I doubt it, from what I know of both emulators.  The one that was submitted
for Wine is protected mode only, and Gabriel's is real mode only.  I
imagine the ideas and some of the code from Gabriel's emulator could
be adapted to this use, but it definitely couldn't be used without
some major changes.  It might be a good place to start, tho.

		Brad Boyer
		flar@pants.nu


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Re: [Fwd: Latest version of CPU emulator] (fwd)

[Gabriel Paubert]

On Wed, 18 Aug 1999, Brad Boyer wrote:

> 
> Geert Uytterhoeven wrote:
> > Perhaps Gabriel's 486SX emulator can be included as an optimization?
> 
> I doubt it, from what I know of both emulators.  The one that was submitted
> for Wine is protected mode only, and Gabriel's is real mode only.  I
> imagine the ideas and some of the code from Gabriel's emulator could
> be adapted to this use, but it definitely couldn't be used without
> some major changes.  It might be a good place to start, tho.

Actually adding protected mode (segmentation) is not that complex,
but adding paging (like Bochs) would be an enormous task I'm not ready to 
undertake. Adding the FPU is feasible but not a simple job (MMX is easy).

My goal was the smallest possible emulator to interpret BIOS ROM and
that's how it has stayed until now. It is reasonably fast (around 6 MIPS
on a 200 MHz 603e) only because it entirely fits into L1 cache (except
plain 603). I could improve the speed slightly (20-30%), at some cost in
size, at least I believe so.

Still the best thing in my code is how the flags are emulated IMHO.

	Regards,
	Gabriel.


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