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==Description==
The PEPE system was based on a number of interconnected chassis. Each of the main Processing Element Bays could hold 36 Processing Elements (PEs), arranged in four rows of nine PEs. A separate, similar, chassis held the
The PE consisted of three main [[Execution unit|functional units]], a [[floating point processor]] (the Arithmetic Unit, AU) that could perform basic
Associative addressing was used in PEPE to allow it to quickly correlate new measurements to existing information. For instance, a particular radar may sweep a section of the sky every 2 seconds. On one such sweep it might see an object in a certain ___location, and the system has to quickly decide whether this is a new ''blip'' or an update of an existing one. The memory system is designed to produce a sort of [[hash code]] of this information that is used to retreive the data, as opposed to searching through memory for possible matches based on the fields in the data.<ref name=pepebook/>
Each processing element contained a minimum of control logic, the bulk of the control being concentrated in the common control unit. The control unit read instructions from memory, decoded them, and issued them to all processing elements simultaneously so that the elements were required to execute the same instruction at the same time. The elements were capable of executing a complete single address instruction including reading and writing the data.<ref name=silogic/>▼
▲Each processing element contained a minimum of control logic, the bulk of the control being concentrated in the common control unit. The control unit read instructions from memory, decoded them, and issued them to all processing elements simultaneously so that the elements were required to execute the same instruction at the same time. The elements were capable of executing a complete single address instruction including reading and writing the data.<ref name=silogic/> The program as a whole was stored on and fed into PEPE from a front-end system, originally a [[CDC 7600]].<ref name=pepebook/>
A [[Burroughs B1700]] computer system was used as a test and diagnostic computer. A custom software package, called TRANSET, which executed on the B1700 was used to debug and maintain PEPE's processing elements. Burroughs delivered PEPE to the Ballistic Missile Defense Advanced Technology Center (part of US Army's Strategic Defense Command) in [[Huntsville, Alabama]] in 1976.<ref name=Ford/> 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.<ref name=silogic/>▼
The system as a whole operated in a lock-step fashion, able to perform one floating point instruction per cycle. The system normally ran at 1 MHz, so each PE performed about 1 MFLOPS, and the system as a whole around 288 MFLOPS. The integer instructions were about 100 times faster, with the system as a whole running about 2,880 MIPS. This was much faster than any machine of the era.<ref name=pepebook/>
▲A [[Burroughs B1700]] computer system was used as a test and diagnostic computer.
==Notes==
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