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Path: utzoo!mnetor!seismo!rochester!kodak!elmgate!jdg
From: jdg@elmgate.UUCP (Jeff Gortatowsky)
Newsgroups: net.micro.atari16,net.micro.amiga,net.micro.68k
Subject: 68000 Memory Managment
Message-ID: <508@elmgate.UUCP>
Date: Wed, 13-Aug-86 07:53:54 EDT
Article-I.D.: elmgate.508
Posted: Wed Aug 13 07:53:54 1986
Date-Received: Thu, 14-Aug-86 04:22:42 EDT
Organization: Eastman Kodak Co., Rochester, NY
Lines: 20
Keywords: 68000 atari amiga 68k mmu
Xref: mnetor net.micro.atari16:1592 net.micro.amiga:4236 net.micro.68k:1127

With all the talk of the new CoCo's memory management system and the
discussions wondering why a 68000 was not used I have the following
thoughts (yes I have ONE now and again :^> )

If memory serves me correct the 68000 can not restart/resume a bus faulted
instruction.  So regardless of what mkind of MMU you try to hang on it, it
can not overcome this problem.  As I understand it,  the 68000 does NOT
ensure the address pointed to on the stack, is the address of the fault
instruction.  Therefore you can't restart the instruction and 68000 does
not dump it's micro-state, so you can't resume the faulted instruction.  Is
this about right?   Motorola you out there?  Guy Harris, this about the
scheme of things?  Henry of UTZOO, this acurate?

BTW the 68010 fixes this.


-- 
Jeff Gortatowsky       {allegra,seismo}!rochester!kodak!elmgate!jdg
Eastman Kodak Company  
<Kodak won't be responsible for the above comments, only those below>