Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!microsoft!alonzo
From: alonzo@microsoft.UUCP (Alonzo GARIEPY)
Newsgroups: comp.sys.handhelds
Subject: Re: HP28 Emulator (Was: Re: (none) --- HP-28S Exponentiation)
Keywords: Emulating the Saturn Processor on an x86
Message-ID: <52101@microsoft.UUCP>
Date: 8 Mar 90 03:21:30 GMT
References: <364@images1.Waterloo.NCR.COM> <1090@tuvie> <1143@tuvie> <52051@microsoft.UUCP>
Reply-To: alonzo@microsoft.UUCP (Alonzo GARIEPY)
Organization: Microsoft Corp., Redmond WA
Lines: 20

In article <52051@microsoft.UUCP> I wrote:
> With a 16 bit 286 running at 16 MHz, you would have 64 times the 
> speed.  That is easily enough to emulate the Saturn at several 
> times the speed of the 28.

I was not suggesting that the *emulator* would run 64 times faster than
the 28, just several times faster, on average.  Portable C would be nice,
but hand-optimized assembler is probably the only way to go.  I would
appreciate a look at the source code of any existing Saturn emulators.

We have a virtual cpu emulator here at Microsoft that uses some very
clever tricks to get optimal performance.  I have no doubt there is room 
for some of the same in emulating the Saturn.

The suggestion that each field variant of an instruction might require
separate emulation is well taken.  The best approach may be to generate
the code for all these variants mechanically.

Alonzo Gariepy
alonzo@microsoft