NON-UNIFORM MEMORY ACCESS (NUMA) DATA PROCESSING SYSTEM THAT PERMITS MULTIPLE CACHES TO CONCURRENTLY HOLD DATA IN A RECENT STATE FROM WHICH DATA CAN BE SOURCED BY SHARED INTERVENTION

A non-uniform memory access (NUMA) computer system includes first and second processing nodes that are each coupled to a node interconnect. The first processing node includes a system memory and first and second processors that each have a respective one of first and second cache hierarchies, which are coupled for communication by a local interconnect. The second processing node includes at least a system memory and a third processor having a third cache hierarchy. The first cache hierarchy and the third cache hierarchy are permitted to concurrently store an unmodified copy of a particular cache line in a Recent coherency state from which the copy of the particular cache line can be sourced by shared intervention. In response to a request for the particular cache line by the second cache hierarchy, the first cache hierarchy sources a copy of the particular cache line to the second cache hierarchy by shared intervention utilizing communication on only the local interconnect and without communication on the node interconnect.