Patent ID: 8543771
Filing Date: 2013-09-24
Classification: G06F

Abstract:
1. A method for maintaining cache coherence using a distributed directory with event driven updates, the method comprising: providing a plurality of cache-coherent multiprocessors, wherein the plurality of cache-coherent multiprocessors are connected via a system interconnect, wherein the system interconnect only supports directed request and response packet deliveries; ensuring successful forwarding of a response packet is not dependent on any concurrently-active request packet; providing a set of stable coherent cache states and a set of unstable coherent cache states for the plurality of cache-coherent multiprocessors; in response to shared accesses attempting to access a previously modified cache-line address, converting a memory state from modified to shared by utilizing a washing technique; avoiding the washing technique on any of infrequent read-only and mixed read/write accesses; and avoiding deadlocks by placing to-be-executed command codes in returned response packets when request-forwarding queues are any of full and not present.