1. A multiprocessor system comprising: a plurality of processor clusters coupled by a network, wherein the plurality of processor clusters includes at least first and second processor clusters each containing multiple processors coupled by a cluster interconnect; and a respective processor communication register (PCR) internal to at least one processor in each of the first and second processor clusters, wherein each PCR has a plurality of sectors from which the processor can retrieve information stored in each sector, and wherein each of the plurality of sectors is allocated for store access by only a respective associated processor cluster of the plurality of processor clusters, and wherein each processor cluster of the plurality of processor clusters updates its associated sector within the plurality of sectors such that when a sector is updated by its associated processor cluster, each processor cluster has immediate access to the updated information.