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From: fsset@bach.lerc.nasa.gov (Scott E. Townsend)
Newsgroups: comp.sys.amiga.advocacy,comp.sys.amiga.programmer
Subject: Re: 88000 in the Amiga (Re: An interesting idea...)
Message-ID: <1991May14.165718.19646@eagle.lerc.nasa.gov>
Date: 14 May 91 16:57:18 GMT
References: <1991May14.130905.9577@sugar.hackercorp.com> <1991May14.145528.23369@neon.Stanford.EDU>
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In article <1991May14.145528.23369@neon.Stanford.EDU> torrie@cs.stanford.edu (Evan Torrie) writes:
>peter@sugar.hackercorp.com (Peter da Silva) writes:
>
>>I've been thinking about how you would use something like an 88000 in an Amiga.
>>It'd make a killer coprocessor at first. Run the Exec on the 88000 as well as
>>the 68000, so that C programs could be compiled for the 88000 and still work.
>>The only really hairy parts would be Forbid() and Disable()... the synch
>>primitives. I think that at first these primitives will have to stall both
>>CPUs, or it'd be too hard to port stuff to the 88000 side.
>
>>Make it an 88000 and you don't have to worry about endianism. What about
>>alignment... what's the 88000's alignment requirements.
>
>  From the 88100 User's Manual:
>
>"All instructions and data words are aligned on word (modulo 4)
>address boundaries, precluding the need for the two lowest order
>address lines and misaligned accesses"
>
>-- 
>------------------------------------------------------------------------------
>Evan Torrie.  Stanford University, Class of 199?       torrie@cs.stanford.edu   
>"Lay me place and bake me pie, I'm starving for me gravy... Leave my shoes
>and door unlocked, I might just slip away - hey - just for the day."

Sorry, but only part of the truth.  Doublewords have to be on doubleword
boundaries.  (Not saying Moto is wrong, just that the above excerpt isn't
the complete story)

Doublewords are used for double-precisioni FP _AND_ saves/restores during
function entry/exit (at least on the compiler I use)  So you _have_ to keep
the stack doubleword aligned or you get a misaligned access exception.

-- 
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Scott Townsend               |   Mail Stop: 5-11
NASA Lewis Research Center   |   Email: fsset@bach.lerc.nasa.gov
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