Upgrading of snooper cache state mechanism for system bus with read/castout (RCO) address transactions

摘要

Upon snooping a combined data access and castout/deallocate operation initiating by a horizontal storage device, snoop logic determines, from coherency state information appended to either the combined operation or the combined response to the operation, whether the coherency state of the victim may be upgraded within the subject storage device. If so, the coherency state is upgraded to improve global data storage management. For instance, a cache line may be upgraded from the shared coherency state to the exclusive coherency state to improve data storage management under a given replacement policy.