An array processor contains severals processing elements (PEs) which operate in parallel under the control of a signal control unit(CU).A processing element is an arithmetic and logic unit (ALU) with attached registers and local memory.It does not have instruction decoding capability .the control unit has its own memory . The control unit control the execution of the system and user programs . The control unit decodes all the instructions . The scaler or control-type instructions are directly executed in the contrl unit .Vector instructions are transmitted to PEs for distributed execution . All the PEs execute the same instruction under the control of the control unit .Vectors operands are stored in the local memories of PEs before they execute an instruction in parallel on different operands . These operand are loaded into the local memories from an external source via the system data bus or via the CU using control bus ..An array processor processes single instruction and multiple data streams (SIMD), that is the saame instructions is to be executed on an array of data usualyy involves matrix computations . Array processors are also called SIMD computers Array computers are very much suitable for vector processing but difficult to program as computer to pipeline computrs .
An array processor is attached to host computer which is a general purpose computr . The host computers performs the task of resource arrangement and I/O supervisions . The control unit of the array processor directly controols the execution of programs . The host computer acts as an operating manager of the entire system using consisting of the host computer and the array processor . The host computers perform executive and I/O functions with outside world . An array processor is a back-end, attached computer and is a special purpose machine . They array processors are not popular among commercial computer manufactures.
Examples of array processors are Illliac IV (1972),Burroughs Corporation's BSP ,Goodyear Aerospace Corporatio's MPP and CM-2 Illiac IV was develpoed at the University of Illionois in tthe 1960s. It was fabricated in 1972 by the Burroughs Corporations . It contained 64 PEs under the control of one CU . It has local memories attached to PEs. It works with the host computer Burroughs B6500 .
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