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Superscalar instruction issue in an asynchronous microprocessor

Philip B. Endecott


This paper describes the implementation of the instruction issuer for a superscalar asynchronous microprocessor, SCALP, as a case study in asynchronous design. The issuer accepts five instructions at a time from the memory interface and issues them out of order to five parallel functional units. SCALP's architecture is designed to reduce the complexity of the instruction issuer by removing the need to detect dependencies between instructions as they are issued. The design has a regular cellular structure suitable for VLSI implementation. Its performance is sufficient that it does not form a bottleneck in the SCALP pipeline.

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