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From: gnu@l5.uucp (John Gilmore)
Newsgroups: net.rumor,net.micro.68k
Subject: Re: Speedy 68020
Message-ID: <226@l5.uucp>
Date: Sun, 27-Oct-85 23:55:06 EST
Article-I.D.: l5.226
Posted: Sun Oct 27 23:55:06 1985
Date-Received: Wed, 30-Oct-85 06:23:48 EST
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Organization: Nebula Consultants in San Francisco
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It's certainly possible that a single 68020 in a lab can be pushed to
32MHz.  It helps a lot, as was pointed out by someone from Intel in
another newsgroup, to change the voltage and to cool the chip as much
as possible.  Getting a sample running 32MHz with freon spray on it is
different from being able to produce chips that run that way across the
full temperature and voltage range.  But if the rumor is true, it does
indicate that the chip is limited by power or temperature or
fabrication tolerances (mechanical design), rather than by switching
speed or electronic design.

One technique usable to see what parts of the chip are limiting it
is to run it at various clock rates and see what kind of failures
appear.  This may be where this 32MHz 68020 is being used.  For
example, the kind of errors that have been described on Vax 785's
(carry propagation across 30 bits) might crop up, indicating that
the adder is the next bottleneck.  Chips run this way are not really
expected to function; they're expected to point the way by how they fail.
The next time the chip mask is fixed up, they can improve the adder,
which probably improves the yield of 16.67MHz chips and 12MHz chips too.