Efficient region coherence protocol for clustered shared-memory multiprocessor systems

Abstract

A system and method of a region coherence protocol for use in Region Coherence Arrays (RCAs) deployed in clustered shared-memory multiprocessor systems which optimize cache-to-cache transfers by allowing broadcast memory requests to be provided to only a portion of a clustered shared-memory multiprocessor system. Interconnect hierarchy levels can be devised for logical groups of processors, processors on the same chip, processors on chips aggregated into a multichip module, multichip modules on the same printed circuit board, and for processors on other printed circuit boards or in other cabinets. The present region coherence protocol includes, for example, one bit per level of interconnect hierarchy, such that the one bit has a value of '1' to indicate that there may be processors caching copies of lines from the region at that level of the interconnect hierarchy, and the one bit has a value of '0' to indicate that there are no cached copies of any lines from the region at that respective level of the interconnect hierarchy.