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From: rcfische@polyslo.CalPoly.EDU (Raymond C. Fischer)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Reforming Mac Programming
Message-ID: <261189c1.4ce@polyslo.CalPoly.EDU>
Date: 29 Mar 90 04:06:25 GMT
References: <13828@eagle.wesleyan.edu> <5492@okstate.UUCP> <1169@ra.cs.Virginia.EDU>
Reply-To: rcfische@polyslo.CalPoly.EDU (Raymond C. Fischer)
Organization: Cal Poly State University -- San Luis Obispo
Lines: 26


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.

>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.


Ray Fischer
rcfische@polyslo.calpoly.edu