International Business Machines Corporation

William K Rodiger

Donald W Price

Yee-Ming Ting

Michael Ignatowski

Lishing Liu

Matthew A Krygowski

Gregory Salyer

Patrick M Gannon

Forrest A Reiley

Michael P Witt

Jon E Thorson

An improved arbitration system is disclosed for arbitrating signals at a plurality of input nodes to output nodes where each input node can access any output node. The system includes a FIFO (first-in-first-out) input queue for each node and means for arbitrating the top of each queue for providing the arbitrated output to a given node and means when the top of the input queue has no request for a given node arbitrating the requests from the next to the top entry of the input queues and providing the data from the next to top entry associated with the arbitrated request to the given node.

Look-ahead priority arbitration system and method

A coherence directory and its methods of operation are disclosed for private processor caches in a multiple processor system to control data coherence in the system. It provides cross-invalidate (XI) controls for the assignment of exclusive and public ownership to data units in the processor caches, including required cross-invalidation of data units among the processor caches to obtain data coherence in the system in an efficient manner. The coherence directory can be used in a multiple processor system with or without any shared second level (L2) cache, shared or private. When a shared L2 cache is used to improve system access time, the coherence directory can also be used as the second level directory for the shared L2 cache and eliminate the need for any additional L2 directory(s).

Coherence control by data invalidation in selected processor caches

An N.times.M matrix adapted to couple N inputs from N processor to M basic storage modules is disclosed. The system includes arbitrators and gating means for each output responsive to request signals for simultaneously coupling data from a plurality of processors to requested basic storage modules under arbitrator control.

N.times.M round robin order arbitrating switching matrix system

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Sudbury, NY, United States of America

William K Rodiger