05319766 is referenced by 83 patents and cites 14 patents.

A processor apparatus for use in a multiprocessor computer system having a main memory storing a plurality of data items and being coupled to a bus operating according of a SNOOPY protocol. The processor apparatus includes a processor, a primary cache, a backup cache and a bus interface. The backup cache memory a first TAG store comprising a plurality of VALID indicators, one VALID indicator for each of the data items currently contained in the backup cache memory. The primary cache memory includes a second TAG store comprising a plurality of address indicators and a plurality of VALID indicators, one address indicator and one VALID indicator for each of the data items currently contained in the primary cache memory. The interface includes a duplicate TAG store coupled to the primary cache memory, the duplicate TAG store consisting of a copy of the address indicators of the second TAG store. The bus interface is coupled to the processor, the backup cache memory and to the bus. The bus interface operates in accordance with a SNOOPY protocol to monitor transactions on the bus for write transactions affecting data items in the corresponding backup cache memory having set VALID indicators. The bus interface will invalidate or update each VALID data item of the backup cache memory when there is a write transaction affecting data item and assert an invalidate signal for an affected data item indicated by the address indicators of the duplicate TAG store. The invalidate signal causes the VALID indicator in the second TAG store for the affected data item to be cleared.

Title
Duplicate tag store for a processor having primary and backup cache memories in a multiprocessor computer system
Application Number
7/874289
Publication Number
5319766
Application Date
April 24, 1992
Publication Date
June 7, 1994
Inventor
Barry A Maskas
Sterling
MA, US
Nitin D Godiwala
Boylston
MA, US
Jeffrey A Metzger
Leominster
MA, US
Kurt M Thaller
Acton
MA, US
Agent
Kenyon & Kenyon
Assignee
Digital Equipment Corporation
MA, US
IPC
G06F 12/08
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