Apollo PRISM

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PRISM (Parallel Reduced Instruction Set Multiprocessor) was Apollo Computer's high-performance CPU used in their DN10000 series workstations. It was for some time the fastest microprocessor available, a high fraction of a Cray-1 in a workstation. Hewlett-Packard purchased Apollo in 1989, ending development of PRISM, although some of PRISM's ideas were later used in HP's own HP-PA Reduced instruction set computer (RISC) and Itanium processors.

PRISM was based on what would be known today as a VLIW-design, while most efforts of the era, 1988, were based on a more "pure" RISC approach. In early RISC designs, the core processor was simplified as much as possible in order to allow more of the chip's real-estate to be used for registers and simplifying the addition of instruction pipelines for improved performance.