Abstract: L1 cache synonyms in a two-level cache system are detected and resolved by logic in the L2 cache. Duplicate copies of the L1 cache tags and state (“Dtags”) are maintained in the L2 cache. After a miss occurs in the L1 cache, the Dtags in the second-level cache that correspond to all possible synonym locations in the L1 cache are searched for synonyms. If a synonym is found, the L2 cache notifies the L1 cache where the requested cache line can be found in the L1 cache. The L1 cache then copies the cache line from the location where the synonym was found to the location where the miss occurred, and it invalidates the cache line at the original location. The Dtags in the second-level cache are updated to reflect the changes made in the L1 cache.

Abstract: An invalid-to-dirty request permits a transition from an invalid memory state to a dirty state without requiring an up-to-date copy of the memory. The present invention is a system for supporting invalid-to-dirty memory transactions in an aggressive cache coherence protocol that minimizes directory entry locking. The nodes of a multiprocessor system each include a protocol engine that is configured to implement a distinct invalidation request that corresponds to an invalid-to-dirty memory transaction. If node O receives this distinct invalidation request while waiting for a response to an outstanding request for exclusive ownership, the protocol engine of node O is configured to treat the distinct invalidation request as applying to the memory line of information that is the subject of the outstanding request for exclusive ownership.

Abstract: L1 cache synonyms in a two-level cache system are detected and resolved by logic in the L2 cache. Duplicate copies of the L1 cache tags and state (“Dtags”) are maintained in the L2 cache. After a miss occurs in the L1 cache, the Dtags in the second-level cache that correspond to all possible synonym locations in the L1 cache are searched for synonyms. If a synonym is found, the L2 cache notifies the L1 cache where the requested cache line can be found in the L1 cache. The L1 cache then copies the cache line from the location where the synonym was found to the location where the miss occurred, and it invalidates the cache line at the original location. The Dtags in the second-level cache are updated to reflect the changes made in the L1 cache.

Abstract: An invalid-to-dirty request permits a transition from an invalid memory state to a dirty state without requiring an up-to-date copy of the memory. The present invention is a system for supporting invalid-to-dirty memory transactions in an aggressive cache coherence protocol that minimizes directory entry locking. The nodes of a multiprocessor system each include a protocol engine that is configured to implement a distinct invalidation request that corresponds to an invalid-to-dirty memory transaction. If node O receives this distinct invalidation request while waiting for a response to an outstanding request for exclusive ownership, the protocol engine of node O is configured to treat the distinct invalidation request as applying to the memory line of information that is the subject of the outstanding request for exclusive ownership.