Patent ID: 7032078

Claim:
A multiprocessing system comprising: a plurality of clients; wherein at least two of the plurality of clients comprise processing subsystems, each including a cache memory; and wherein at least one of the plurality of clients comprises a memory subsystem including a directory; and a network separate from said clients; wherein said network includes a switch comprising a plurality of ports, wherein each of said plurality of clients may be coupled to a respective one of said plurality of ports, wherein the switch is configured to: receive a first coherency request from a given client, wherein said first coherency request is not visible to any other of said plurality of clients; and transmit a second coherency request in response to receiving said first coherency request; wherein the switch further comprises a coherency mode storage unit configured to store an indication to control whether the switch will transmit said second coherency request according to a directory protocol or a broadcast protocol; wherein if said second coherency request is transmitted by said switch according to said directory protocol: said second coherency request is transmitted by said switch to only said client comprising said memory subsystem; said directory is accessed by said memory subsystem; and responsive coherency commands are provided to one or more of said plurality of processing subsystems dependent upon information contained within said directory.