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From: chris@usc-oberon.UUCP (Christopher Ho)
Newsgroups: comp.arch
Subject: Re: Speed is the one true performance metric
Message-ID: <419@usc-oberon.UUCP>
Date: Fri, 21-Nov-86 01:19:14 EST
Article-I.D.: usc-ober.419
Posted: Fri Nov 21 01:19:14 1986
Date-Received: Fri, 21-Nov-86 20:23:29 EST
References: <1510@batcomputer.tn.cornell.edu> <1079@rti-sel.UUCP>
Reply-To: chris@usc-oberon.UUCP (Christopher Ho)
Organization: USC Computing Services, Los Angeles, CA
Lines: 13

Two anecdotes about VAX '780s...

There was a story I heard a while ago where an early '780 had not-quite-
up-to-spec components, and (similar to the ns32k mentioned earlier)
increments of small negative numbers (eg -1) would yield unpredictable
results because the carry didn't propagate fast enough...

At one point we had a user on our '780 whose Fortran program would
generate access violations at a particular point in his program.  What
was interesting was that the very same binary wouldn't do this when run
on another '780 or our '750s.  Turned out to be the FP board, although
that took our 3rd party maintenance weeks to find out (the old swap 1
board, wait, try again, trick).