05222224 is referenced by 110 patents and cites 39 patents.

A method for insuring data consistency between a plurality of individual processor cache memories and the main memory in a multi-processor computer system is provided which is capable of (1) detecting when one of a set of predefined data inconsistency states occurs as a data transaction request is being processed, and (2) correcting the data inconsistency states so that the operation may be executed in a correct and consistent manner. In particular, the method is adapted to address two kinds of data inconsistency states: (1) A request for a operation from a system unit to main memory when the location to be written to is present in the cache of some processor unit-in such a case, data in the cache is "stale" and the data inconsistency is avoided by preventing the associated processor from using the "stale" data; and (2) when a read operation is requested of main memory by a system unit and the location to be read may be written or has already been written in the cache of some processor--in this case, the data in main memory is "stale" and the data inconsistency is avoided by insuring that the data returned to the requesting unit is the updated data in the cache. The presence of one of the above-described data inconsistency states is detected in a SCU-based multi-processing system by providing the SCU with means for maintaining a copy of the cache directories for each of the processor caches. The SCU continually compares address data accompanying memory access requests with what is stored in the SCU cache directories in order to determine the presence of predefined conditions indicative of data inconsistencies, and subsequently executes corresponding predefined fix-up sequences.

Title
Scheme for insuring data consistency between a plurality of cache memories and the main memory in a multi-processor system
Application Number
306776
Publication Number
5222224
Application Date
July 9, 1991
Publication Date
June 22, 1993
Inventor
David J Webb
Berlin
MA, US
Ricky C Hetherington
Northboro
MA, US
Tryggve Fossum
Northboro
MA, US
Stephen J DeLaHunt
Harvard
MA, US
Scott Arnold
Sutton
MA, US
Michael E Flynn
Grafton
MA, US
Agent
Arnold White & Durkee
Assignee
Digital Equipment Corporation
MA, US
IPC
G06F 12/08
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