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From: @S1-A.ARPA,@MIT-MC.ARPA:cdl@cmu-cs-k.arpa
Newsgroups: net.space
Subject: Re: Space Shuttle Computers
Message-ID: <2362@mordor.UUCP>
Date: Fri, 21-Jun-85 15:51:19 EDT
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Posted: Fri Jun 21 15:51:19 1985
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From: Douglass.Locke@CMU-CS-K.ARPA

The four (not five) Shuttle computers are indeed IBM AP-101 processors.
They are environmentally hardened 32 bit machines which bear NO
resemblance to IBM 360's or any other commercial computer, either in
architecture or in construction.  Although all the processors are
identical, one contains a different software package written by
Rockwell to avoid the potential of a single software problem stopping
all the computers simultaneously.  Before one criticizes the packaging,
or the memory technology chosen, it would perhaps be appropriate to
investigate the difficulties of handling an environment with potential
extremes of temperature, vibration, shock, EMI, and radiation, with
acceptable reliability, and in a vehicle which is totally dependent on
the equipment.  When NASA was specifying the equipment, it was in the
mid-70's and there was no applicable experience with the actual shuttle
environment, so a conservative approach was certainly justified.  The
IBM AP-101 is one of an extensive line of machines for such
environments with a variety of speeds, form factors, memory
technologies, etc., each designed to cope with different environmental
and application requirements.

				-- Doug Locke