MAINTAINING HIGH SNOOP TRAFFIC THROUGHPUT AND PREVENTING CACHE DATA EVICTION DURING AN ATOMIC OPERATION

摘要

An embodiment of the invention provides an apparatus that permits snoop filtering (Ref. 51) to occur while an atomic operation is pending. The apparatus includes first and second request queues and a cache. The first request queue (Ref. 52) tracks cache access requests, while the second request queue (Ref. 54) tracks snoops that have yet to be filtered. The cache includes a dedicated port for each request queue. The first port is dedicated to the first request queue and is a data-and-tag read-write port, permitting modification of both a cache line's data and tag. In contrast, the second port is dedicated to the second request queue and is a tag-only port. Because the second port is a tag-only port, snoop filtering can continue while a cache line is locked without fear of any modification of the data associated with the atomic address. In another embodiment, the present invention further includes an atomic address block that prevents eviction of a cache address during an atomic operation.