Abstract: Methods and apparatus are provided for reusing snoop responses and data phase results in a cache controller. A cache controller receives a broadcast combined snoop response from a bus controller, wherein the broadcast combined snoop response corresponds to an incoming bus transaction BTR1 corresponding to a cache transaction CTR1 for an entry in at least one cache and wherein the combined snoop response is a combination of at least one snoop response from a plurality of cache controllers; receives broadcast cache line data from a source cache as instructed by the bus controller for the entry during a data phase; and processes a subsequent cache transaction CTR2 for the entry based on one or more of the broadcast combined snoop response and the broadcast cache line data.

Abstract: Methods and apparatus are provided for reusing snoop responses and data phase results in a bus controller. A bus controller receives an incoming bus transaction BTR1 corresponding to an incoming cache transaction CTR1 for an entry in at least one cache; issues a snoop request with a cache line address of the incoming bus transaction BTR1 for the entry to a plurality of cache controllers; collects at least one snoop response from the plurality of cache controllers; broadcasts a combined snoop response to the plurality of cache controllers, wherein the combined snoop response is a combination of the snoop responses from the plurality of cache controllers; and broadcasts cache line data from a source cache for the entry during a data phase to the plurality of cache controllers, wherein a subsequent cache transaction CTR2 for the entry is processed based on the broadcast combined snoop response and the broadcast cache line data.

Abstract: Methods and apparatus are provided for cache line sharing among cache controllers. A cache comprises a plurality of cache lines; and a cache controller for sharing at least one of the cache lines with one or more additional caches, wherein a given cache line shared by a plurality of caches corresponds to a given set of physical addresses in a main memory. The cache controller optionally maintains an ownership control signal indicating which portions of the at least one cache line are controlled by the cache and a validity control signal indicating whether each portion of the at least one cache line is valid. Each cache line can be in one of a plurality of cache coherence states, including a modified partial state and a shared partial state.

Abstract: Shared cache line data is merged in a bus controller by issuing a snoop request to a plurality of cache controllers with a cache line address for which a bus transaction is performed; collecting snoop responses from the plurality of cache controllers, wherein a snoop response from a given cache controller comprises a cache state of the cache line address in a given cache associated with the given cache controller, and an ownership control signal identifying which portions of the cache line are controlled by the given cache; collecting data responses from the cache controllers, wherein the data response from a given cache controller comprises a data value from the cache line address; merging the data values from the cache controllers based on the ownership control signals to obtain a merged data value; and broadcasting the merged data value to the cache controllers.

Abstract: Methods and apparatus are provided for reusing snoop responses and data phase results in a cache controller. A cache controller receives a broadcast combined snoop response from a bus controller, wherein the broadcast combined snoop response corresponds to an incoming bus transaction BTR1 corresponding to a cache transaction CTR1 for an entry in at least one cache and wherein the combined snoop response is a combination of at least one snoop response from a plurality of cache controllers; receives broadcast cache line data from a source cache as instructed by the bus controller for the entry during a data phase; and processes a subsequent cache transaction CTR2 for the entry based on one or more of the broadcast combined snoop response and the broadcast cache line data.

Abstract: Methods and apparatus are provided for reusing snoop responses and data phase results in a bus controller. A bus controller receives an incoming bus transaction BTR1 corresponding to an incoming cache transaction CTR1 for an entry in at least one cache; issues a snoop request with a cache line address of the incoming bus transaction BTR1 for the entry to a plurality of cache controllers; collects at least one snoop response from the plurality of cache controllers; broadcasts a combined snoop response to the plurality of cache controllers, wherein the combined snoop response is a combination of the snoop responses from the plurality of cache controllers; and broadcasts cache line data from a source cache for the entry during a data phase to the plurality of cache controllers, wherein a subsequent cache transaction CTR2 for the entry is processed based on the broadcast combined snoop response and the broadcast cache line data.

Abstract: Methods and apparatus are provided for reusing prior tag search results in a cache controller. A cache controller is disclosed that receives an incoming request for an entry in the cache having a first tag; determines if there is an existing entry in a buffer associated with the cache having the first tag; and reuses a tag access result from the existing entry in the buffer having the first tag for the incoming request. An indicator can be maintained in the existing entry to indicate whether the tag access result should be retained. Tag access results can optionally be retained in the buffer after completion of a corresponding request. The tag access result can be reused by (i) reallocating the existing entry to the incoming request if the indicator in the existing entry indicates that the tag access result should be retained; and/or (ii) copying the tag access result from the existing entry to a buffer entry allocated to the incoming request if a hazard is detected.