Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!usc!apple!keith
From: keith@Apple.COM (Keith Rollin)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Reforming Mac Programming
Message-ID: <39918@apple.Apple.COM>
Date: 29 Mar 90 05:55:22 GMT
References: <13828@eagle.wesleyan.edu> <5492@okstate.UUCP> <1169@ra.cs.Virginia.EDU> <261189c1.4ce@polyslo.CalPoly.EDU>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 33

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:
>>[ much discussion of using SANE vs. direct calls to the FPU ]
>>
>>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.
>
>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.

I don't know if this solution would result in faster code. There are a LOT
of instructions that would have to emulated. Not just things like FCOS or FSUB
or FLOG2. But you would also have to emulate all of the FMOVE instructions.
These FMOVE instructions would have to go through a rather elaborate trap
dispatcher, which would add a lot to execution time. I suppose, on the other
hand (I love arguing with myself), that FMOVE instructions could be optimized
in the dispatcher, and handled rather quickly.

So where does the memory for the FP registers come from. Low memory? Sounds
possible. Are there any other problems that need to be hurdled? The 6888x
raises exceptions; would there be any problem with emulating these?
-- 
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"Argue for your Apple, and sure enough, it's yours" - Keith Rollin, Contusions