--- Pete Turnbull <pete_at_dunnington.u-net.com> wrote:
> On Jan 14, 14:56, Bruce Robertson wrote:
>
> > Yes, I seem to remember that with the 68000, there was an interaction
> > with the Bus Fault signal... something to do with what state got saved
> > on the stack; I don't remember the exact details
After a bus fault, there was not enough information on the stack to
properly do an instruction restart from where the bus-fault occured.
> Oops, I forgot about that. You're right; the 68010 saves slightly more
> state on the stack than the early 68000. I have a feeling that was fixed
> in later 68000; some traps save more state than others.
Not as far as I know... the quantity of bytes pushed on the stack should
be constant for a given member of the 68K family. A lot of older software
for the Amiga that did things with the stack (debugging tools, mostly)
assumed certain things relating to the stack - it became confused on
the '010 and up because the number of bytes did change for certain
traps (like bus error). I have the details at home, not with me, in my
Motorola books, or I'd post them here. Eventually, people learned to
ask the OS what was going on, rather than paw through the stack
indescriminantly, kinda like when people got burned on the first Fatter
Agnus Amigas - 1Mb of CHIP and 0Mb of FAST RAM - broke all kinds of
software that asked for a buffer of FAST RAM instead of "fastest available
RAM".
> You can't get 68010s any more, unless you can find old stock somewhere
> :-(
> You can still get 68000s and 68020s.
That's not surprising. Even when they were current, we had a hard time
getting 68010 chips for our products. We paid $45 each for them at a
time when the 68000P8 was about $3 (eventually, I found them at a
surplus/overstock electronics dealer for $10).
At the moment, I have dozens of 68000L8s and one tube of 68010P10s. I
hope I never have to look for any more 68010s.
-ethan
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Received on Tue Jan 15 2002 - 14:19:53 GMT