IBM System/4 Pi

The IBM AP-101B CPU and I/O processor (right) and AP-101S (left)

The IBM System/4 Pi is a family of avionics computers used, in various versions, on the F-15 Eagle fighter, E-3 Sentry AWACS, Harpoon Missile, NASA's Skylab, MOL, and the Space Shuttle, as well as other aircraft. Development began in 1965, deliveries in 1967.[1] They were developed by the IBM Federal Systems Division and produced by the Electronics Systems Center in Owego, NY.[2]

It descends from the approach used in the System/360 mainframe family of computers, in which the members of the family were intended for use in many varied user applications. (This is expressed in the name: there are 4π steradians in a sphere, just as there are 360 degrees in a circle.[3]) Previously, custom computers had been designed for each aerospace application, which was extremely costly.

  1. ^ IBM 1967, p. 1-3 (9).
  2. ^ IBM 1967, p. iv.
  3. ^ IBM 1967, Foreword, p. iii/iv (6).