Bell began researching the concept in the mid-1960s as a way to provide high-performance computing support for the needs of anti-ballistic missile (ABM) systems.
[1][2][3] A single PEPE system was built by Burroughs Corporation in the 1970s, by which time the US Army's ABM efforts were winding down.
Missile fleets of both the US and USSR were growing through the 1960s, but a bigger issue was the rapid increase in the number of warheads as a result of the move to multiple independently targetable reentry vehicles (MIRV).
[4] An initial testbed system, the "IC model", was built with 16 processors consisting of individual integrated circuits and connected to an IBM 360/65 host.
[2] Testing was apparently successful, but Bell concluded that the machine was too expensive for the sorts of threats being addressed by the Safeguard Program that was being deployed in the 1970s.
A separate, similar, chassis held the Control Unit (CU) and a simple system console that displayed the status.
The elements were capable of executing a complete single address instruction including reading and writing the data.
A custom software package, called TRANSET, which executed on the B1700 was used to debug and maintain PEPE's processing elements.