🚀 go-pugleaf

In article <204@bbxeng.UUCP> scott@bbxeng.UUCP (Scott-Engineering) writes:
>
>Forgive me for showing my ignorance, but, doesn't instruction continuation
>enable features such as dynamic stack allocation?  Are we doomed to
>return to the antiquated "stack probe"?  Does this mean that 68030
>(user mode) software will not always work correctly on the 68040?
>What about page faults?  Is the operating system *really* expected 
>to include an instruction set interpreter so it can simulate
>instruction continuation?  The 386 is suddenly starting to look good
>me.

No - the need for 'stack probe' etc was caused by the 68000 (fixed in
the 68010) which couldn't restart (either restart or continue) from
a bus error (page fault) [it didn't keep enough information around in
its bus error stack frame to tell what it had done, or undo it itself
while delivering the bus error]. Some early vendors actually had 2 68000s,
one which executed the user mode code and was halted in mid instruction
while the other was started to fix the problem ..... thus preserving the
internal state ....

I'm sure Motorola won't make this mistake again .....


	Paul


-- 
Paul Campbell    UUCP: ..!mtxinu!taniwha!paul     AppleLink: D3213
"Free Market": n. (colloq.) a primitive fertility goddess worshipped by an
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