Re: MCL on new 68040 machines

[Gary Byers <gb@cambridge.apple.com>]

    Does anyone know whether MCL runs on the forthcoming 68040 machines
    (I will have a chance to test them, but I do not want to make the
    trip if all I'll see is a nice little bomb)?

    Marc Domenig 

    domenig@urz.unibas.ch


[What forthcoming 68040 machines ?  Oh ...]

Released beta versions of MCL don't interact correctly with the 68040's
caches, which (can) behave differently and are controlled differently
from those on the 030 and 020.  For the lisp to run at all reliably,
the 040's instruction cache would need to be disabled and its data cache
configured in "writethrough" (vice "copyback") mode.  Disabling the
instruction cache will probably have a fairly severe negative effect
on performance.

The final version of MCL 2.0 -will- operate correctly with both 68040
caches enabled.  The code that's at all sensitive to cache-related issues
is buried fairly deep in the lisp kernel; I don't think that it's likely
that we'll be able to offer a patch that would enable released beta versions
to run on 68040s with their caches fully enabled.

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