Cache including a prefetch way for storing prefetch cache lines and configured to move a prefetched cache line to a non-prefetch way upon access to the prefetched cache line

摘要

A cache employs one or more prefetch ways for storing prefetch cache lines and one or more ways for storing accessed cache lines. Prefetch cache lines are stored into the prefetch way, while cache lines fetched in response to cache misses for requests initiated by a microprocessor connected to the cache are stored into the non-prefetch ways. Accessed cache lines are thereby maintained within the cache separately from prefetch cache lines. When a prefetch cache line is presented to the cache for storage, the prefetch cache line may displace another prefetch cache line but does not displace an accessed cache line. A cache hit in either the prefetch way or the non-prefetch ways causes the cache line to be delivered to the requesting microprocessor in a cache hit fashion. The cache is further configured to move prefetch cache lines from the prefetch way to the non-prefetch way if the prefetch cache lines are requested (i.e. they become accessed cache lines). Instruction cache lines may be moved immediately upon access, while data cache line accesses may be counted and a number of accesses greater than a predetermined threshold value may occur prior to moving the data cache line from the prefetch way to the non-prefetch way. Additionally, movement of an accessed cache line from the prefetch way to the non-prefetch way may be delayed until the accessed cache line is to be replaced by a prefetch cache line.