[futurebasic] Re: [FB] Bus error problem

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From: Robert Purves <robert.purves@...>
Date: Tue, 1 Jun 1999 10:37:17 +1200
>>A: What is happening here?
>
>Sounds like the 'ol stale data cache problem.  On certain machines (the
>68040 being particularly notorious) you need to clear the data cache
>periodically otherwise your program will read/write to stale data or jump
>to bogus addresses.  Your harmless code is overfilling the data cache and
>causing it to clean itself out, which gives you current data.

I disagree. The 68040 cache was designed in such a way as _not_ to cause
any such problems. The only programs incompatible with the cache were those
using "self-modifying" code -- an old-fashioned dodgy bush-league
technique, irrelevant to FB programmers.

>The best thing to do would be to find out how to clear the data cache on a
>G3 machine.

The cache systems for PPC, including the backside G3 cache, are of
completely different design from the 68040.

Mark's suggestions imply that:-
(1)  first Motorola, then IBM and Apple, separately and together, contrived
to make mistakes in the cache systems such that FB programs would give bus
errors that are not the programmer's fault.
(2) nobody has noticed these grave design errors until now.

I think there are more credible explanations for bus errors.

Robert