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From: eder@ssc-vax.UUCP (Dani Eder)
Newsgroups: net.space
Subject: Re: Space Shuttle Computers
Message-ID: <29@ssc-vax.UUCP>
Date: Fri, 5-Jul-85 18:10:32 EDT
Article-I.D.: ssc-vax.29
Posted: Fri Jul  5 18:10:32 1985
Date-Received: Sat, 13-Jul-85 09:49:51 EDT
References: <2939@decwrl.UUCP>
Organization: Boeing Aerospace Co., Seattle, WA
Lines: 32

> <>
> > ...the fifth one is different from the other 4; it is made by Rockwell...
> 
> I could be proven wrong, but I am quite sure that all 5 cpus are the same.
> The fifth one, however, was PROGRAMMED by Rockwell rather than IBM.  The 
> quintuple hardware redundancy provides backup for hardware failure.  The 
> separate program for #5 provides a backup for the software.
> 
> BTW, the 5 computers only run as a quintuple redundant set during critical
> phases of the mission (ascent and decent, and perhaps during some of the
> prelaunch activities).  At other times, they are decoupled and given separate
> tasks, with only double or triple redundancy for such things as orbital
> calculations, environment management, and running the arm.

     The following is extracted from a Rockwell International reference book
on the space shuttle:


     The memory capacity of each CPU is 81,920 words. The memory capacity 
of each input-output processor (which intermediates between CPU and real 
world) is 24,576 words.  To accomplish all of the mission phases, approx.
400,000 woeds are required.  To fit the software, it has been divided into
9 parts.  Mass memory is provided by two tape drives totalling 37 Meg.
Each I/O Processor contains 24 processors, each controlling one data bus.
The computers perform 325000 operations/second, and when operating in
a redundant mode compare results 440 times/second.  Each CPU is 7 1/2 x
10 x 19 inches and weighs 57 pounds.  The I/O processors are the same
size and weight.  Each of two mass memories is 7 1/2 x 11 x 15 inches
and weights 22 lbs.

Dani Eder/ Boeing Advanced Space Transportation Organization/ssc-vax!eder
>