Wikipedia's article on the IBM System/4 Pi says:
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. The name of the system refers to the number of steradians (4π) in a sphere. Development began in 1965, deliveries in 1967.
It descends from the approach used in the System/360 mainframe family of computers in that members of the family were intended for use in many varied user applications. Previously custom computers had been designed for each aerospace application, which was extremely costly.
It sounds to me like the idea of providing the System/4 Pi was to provide a bit of standardization, but spaceflight involves an elevated exposure to radiation.
Were there any aspects of the system that were further modified for radiation hardening in spaceflight applications, such as special chips or components or did the standard system already have sufficient hardening?