- IBM System/4 Pi
The
IBM System/4 Pi is a family ofradiation hardened avionics computer s used, in various versions, on theB-52 Stratofortress bomber, theF-15 Eagle fighter,E-3 Sentry ,NASA 'sSkylab space station, MOL, and the Space Shuttle, as well as other aircraft. It descends from theSystem/360 mainframe family of computers.The top-of-the-line 4 Pi is the
AP-101 , used in the B-52. The U.S. Navy used a similar variant in the carrier based A-6E/A-6E TRAM mediumattack aircraft . The Shuttle was controlled by five AP-101s, four of which were arranged in a redundant configuration, with the fifth as backup. Skylab employed the model TC-1, which had a16-bit word length in contrast to the AP-101's 32 bits.The name of the system is derived from the fact that the angular measure of a complete sphere (
solid angle ) is 4πsteradian s, while the angular measure of a complete circle is 360 degrees; hence "System/4 Pi" and "System/360". This implies that System/4 Pi is a version of theIBM System/360 for the three-dimensional world of avionics.References
* [http://www.hq.nasa.gov/office/pao/History/computers/Ch3-2.html "Computers in Spaceflight: The NASA Experience", Ch.3: The Skylab Computer System – Hardware] – From the online version of the NASA report by George Tomayko.
External links
* [http://www-03.ibm.com/ibm/history/exhibits/space/space_shuttle.html IBM Archive: IBM and the Space Shuttle]
* [http://www-03.ibm.com/ibm/history/exhibits/space/space_skylab.html IBM Archive: IBM and Skylab]
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