05878268 is referenced by 41 patents and cites 7 patents.

A computer system including one or more processing nodes, each of which includes one or more subnodes is provided. One of the subnodes (the controller subnode) manages the interface between the processing node and the remainder of the computer system. Other subnodes (snooper subnodes) are employed to store access rights for coherency units within the memory. The processing node's memory is logically divided into portions, and each subnode stores access rights for a particular memory portion. When a transaction is initiated within the processing node, the subnode storing the access rights for the coherency unit affected by the transaction analyzes the access rights and determines if the transaction may complete locally within the processing node. If coherency activity is required, the subnode asserts an ignore signal causing the transaction to be omitted while coherency activity is performed to acquire sufficient access rights. The access rights are updated concurrent with reissue of a transaction for which coherency activity is performed. In this manner, the updated access rights are available to subsequent transactions even though the access rights may be stored in a different subnode than the controller subnode (which performs the reissue transaction). In one embodiment, the updated access rights are conveyed within one of the address phases of the reissue transaction. A bytemask field within one of the address phases is used.

Multiprocessing system configured to store coherency state within multiple subnodes of a processing node
Application Number
Publication Number
Application Date
July 1, 1996
Publication Date
March 2, 1999
Erik E Hagersten
Palo Alto
Conley Rose & Tayon PC
B Noel Kivlin
Sun Microsystems
G06F 15/16
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