Article-I.D.: mordor.2338
Posted: Wed Jun 19 18:35:33 1985
Date-Received: Sun, 23-Jun-85 12:22:36 EDT
Sender: daemon@mordor.UUCP
Lines: 14

From: Gern 

It is my understanding that the Space Shuttle computers are 32-bit machines
(IBM does not seem to make 36-bit machines) and are a scaled down version
of the IBM 360 in a 60 pound package (gross!).   That is, 4 of the computers
are.  The 5th was designed and built by Rockwell (Rockwell doesn't trust IBM
computers either).  I do not know how different the Rockwell machine is to
the IBMs, but it is the only computer that has never failed (it did cause
the sync problems on the very first attempted launch, but only because the
4 IBMs ganged up on it...).

Cheers,
Gern
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Article-I.D.: <2362@mordor.UUCP>
Date: Fri, 21-Jun-85 15:51:19 EDT
Article-I.D.: mordor.2362
Posted: Fri Jun 21 15:51:19 1985
Date-Received: Sat, 29-Jun-85 23:57:46 EDT
Sender: daemon@mordor.UUCP
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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

Article-I.D.: <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
>