Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uflorida!haven!wam!nebel
From: nebel@wam.umd.edu (Chris D. Nebel)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Reforming Mac Programming
Message-ID: <1990Mar29.172204.5338@wam.umd.edu>
Date: 29 Mar 90 17:22:04 GMT
References: <13828@eagle.wesleyan.edu> <5492@okstate.UUCP> <1169@ra.cs.Virginia.EDU> <261189c1.4ce@polyslo.CalPoly.EDU>
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Reply-To: nebel@wam.umd.edu (Chris D. Nebel)
Organization: University of Maryland at College Park
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In article <261189c1.4ce@polyslo.CalPoly.EDU> rcfische@polyslo.CalPoly.EDU (Raymond C. Fischer) writes:
>In article <1169@ra.cs.Virginia.EDU> des7f@uvacs.cs.Virginia.EDU (David Sappington) writes:
>>Why oh why doesn't Apple include a 6888x emulation package with their
>>system software?  Just as the Mac's trap dispatcher handles Axxx
>>"instructions", Apple could easily set up a dispatcher to handle the
>>Fxxx floating point "instructions" on machines w/o an FPU.  Everyone
>>could then use direct calls to the FPU and still have their programs
>>run on a Plus or SE.

Supposedly, this has actually been done.  There was a news bit in Byte
magazine a month or two back about a program called XMath by some German
company that provided software emulation of 68881 and 68020 instructions
on a 68000.  The hitch is that they didn't give any way to contact them:
no address, no phone number, nothing.  Also, they didn't say whether it
was actually finished or just "Real Soon Now".  Does anyone know where
to find these people?

>Good idea.  Perhaps with a different interface, SANE would even become 
>slightly faster.  Programs would certainly be smaller since 68882 
>instructions are smaller than equivalent SANE traps.

They claimed in the article a speedup of about 5x over normal SANE.

>>68020 instructions that are not available on the 68000 could also
>>be emulated by using the "illegal instruction" trap but I don't know
>>if it would be worth doing.
>
>Not possible.  In addition to a few new instructions, the 68020
>also has new addressing modes which do not generate illegal instruction
>traps, but rather just cause general mayhem when used on a 68000.

Well, they claimed that they'd done it, but they could just be misreporting
things... :)


Chris Nebel
nebel@wam.umd.edu