Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!uwvax!puff!scott
From: scott@puff.UUCP (Scott Aschenbach)
Newsgroups: net.micro.atari16,net.micro.amiga,net.micro.68k
Subject: Re: 68000 Memory Managment
Message-ID: <162@puff.UUCP>
Date: Tue, 19-Aug-86 12:08:31 EDT
Article-I.D.: puff.162
Posted: Tue Aug 19 12:08:31 1986
Date-Received: Wed, 20-Aug-86 08:23:42 EDT
References: <508@elmgate.UUCP> <767@ark.UUCP>
Organization: U of Wisconsin CS Dept
Lines: 27
Keywords: 68000 atari amiga 68k mmu
Summary: you can auto-allocate stack space
Xref: mnetor net.micro.atari16:1641 net.micro.amiga:4321 net.micro.68k:1143

In article <767@ark.UUCP>, gijs@ark.UUCP (Gijs Mos) writes:
> In article <508@elmgate.UUCP> jdg@elmgate.UUCP writes:
> ...
> >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.   ...
> 
> You cannot do virtual memory, you cannot auto-allocate stack space, but you
> *can* do multitasking. 
> 
> -- 
> Gijs Mos
You can auto-allocate stack space if you always allocate it the same way
so you know how to recover when you get a fault.  For example, always
update the stack/frame pointers and then clear a memory location before
actually using it.  A bit wasteful, but it may be worth the effort.

I though I heard of someone using pairs of 68000's before the 68010s
came out.  One was set to run just a bit ahead of the other, so that
the first faulted, and the second was in the state the first one should
be in when it was restarted.

It may not be cheap, but don't say it can't be done.

-- 
W. Scott Aschenbach (Deputy Directory of Computing Facilities)
uwvax!scott        scott@rsch.wisc.edu