Patent ID: 7213106

Claim:
A computer system, comprising: a plurality of multiprocessing nodes, each of the plurality of multiprocessing nodes comprising: a first processor; a first cache memory external to and associated with the first processor having a local cache line with a number of entries; and a filter point-to-point connected to the first processor, the filter including a cache memory having a shadow cache line arranged to maintain at least one tag corresponding to data stored in the local cache line, wherein the shadow cache line has more entries allocated for the local cache line than are in the local cache line, wherein, the filter forwards a received broadcast for requested data from a requesting processor to the first processor dependent on the shadow cache line when the shadow cache line contains a tag corresponding to the requested data, wherein the filter sends a message to the requesting processor indicating that no other processor in the computer system includes a copy of the requested data when the shadow cache line does not contain the tag corresponding to the requested data; and wherein the filter removes one of the at least one tag from the shadow cache line when a local cache line miss occurs resulting from referencing the one of the at least one tag.