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From: tim@ism780c.UUCP (Tim Smith)
Newsgroups: net.micro.atari16,net.micro.amiga,net.micro.68k
Subject: Re: 68000 Memory Managment
Message-ID: <3260@ism780c.UUCP>
Date: Tue, 19-Aug-86 17:40:32 EDT
Article-I.D.: ism780c.3260
Posted: Tue Aug 19 17:40:32 1986
Date-Received: Thu, 21-Aug-86 02:18:34 EDT
References: <508@elmgate.UUCP> <767@ark.UUCP>
Reply-To: tim@ism780c.UUCP (Tim Smith)
Organization: Interactive Systems Corp., Santa Monica, CA
Lines: 26
Keywords: 68000 atari amiga 68k mmu
Xref: mnetor net.micro.atari16:1657 net.micro.amiga:4344 net.micro.68k:1147

In article <767@ark.UUCP> gijs@vu44.UUCP (Mos Gijs) writes:
>	...
>	Although this information is not sufficient in general to effect full
>	recovery from the bus error, it does allow software diagnosis.
>	...
>You cannot do virtual memory, you cannot auto-allocate stack space, but you
>*can* do multitasking. 
>

Actually, with a small compiler hack, you *can* auto-allocate stack
space.  The trick is that while in general you can't restart, there
are specific instructions that can be restarted.  tstb is one such
instruction.  The hack to the compiler is to make it generate a
tstb in the function entry code to access the lowest stack address
that the function will use.

I have heard people claim that there is enough information around
after a bus error ( or address error ) to restart most instructions,
if the bus error handler is willing to be clever.  However, I haven't
seen any actual code...  Anyone know if this is true?  If so, what
are the instructions that can't be restarted?
-- 
"I *DO* believe in Mary Worth"

Tim Smith       USENET: sdcrdcf!ism780c!tim || ima!ism780!tim
		Compuserve: 72257,3706          Delphi || GEnie: mnementh