PARTIAL DIRECTORY CACHE FOR REDUCING PROBE TRAFFIC IN MULTIPROCESSOR SYSTEMS

A partial directory cache records addresses of blocks which are known to be cached in a non-exclusive state in any caches currently caching the blocks. If a read command to a block recorded in the partial directory cache is received, one or more probes corresponding to the command may be inhibited. Since probes are selectively inhibited if an affected block is recorded in the partial directory cache, the size of the partial directory cache may be flexible. If a particular block is not represented in the partial directory cache, probes are performed when the particular block is accessed (even if the particular block could have been represented in the partial directory cache). Thus, coherency is maintained even if every non-exclusively cached block is not represented in the partial directory cache.