Dynamically foldable and unfoldable instruction fetch pipeline

Abstract

A dynamically-foldable instruction fetch pipeline receives a first fetch request that includes a fetch virtual address and includes first, second and third sub-pipelines that respectively include a translation lookaside buffer (TLB) that translates the fetch virtual address into a fetch physical address, a tag random access memory (RAM) of a physically-indexed physically-tagged set associative instruction cache that receives a set index that selects a set of tag RAM tags for comparison with a tag portion of the fetch physical address to determine a correct way of the instruction cache, and a data RAM of the instruction cache that receives the set index and a way number that together specify a data RAM entry from which to fetch an instruction block. When a control signal indicates a folded mode, the sub-pipelines operate in a parallel manner. When the control signal indicates a unfolded mode, the sub-pipelines operate in a sequential manner.