Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Patent
1997-04-14
1999-08-17
Cabeca, John W.
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
711158, 711144, 711118, G06F 1200
Patent
active
059408642
ABSTRACT:
A method of reducing memory latency associated with a read-type operation in a multiprocessor computer system is disclosed. When a requesting processing unit issues a message indicating that it desires to read a value from an address of a memory device of the computer system, each cache snoops an interconnect to detect the message, and transmits a response to the message, wherein a shared intervention response is transmitted to indicate that a cache containing an unmodified value corresponding to the address of the memory device can source the value. A priority is associated with each response, and system logic detects each response and its associated priority, and forwards a response with a highest priority to the requesting processing unit. The protocol may include prior-art coherency responses such as an invalid response, a modified intervention response, a shared response, and a retry response. Either the retry response or the shared intervention response may be assigned a highest priority. Since the cache latency can be much less than the memory latency, the read performance can be substantially improved with this new protocol.
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Arimilli Ravi Kumar
Dodson John Steven
Kaiser John Michael
Lewis Jerry Don
Cabeca John W.
Dillon Andrew J.
Henkler Richard A.
International Business Machines - Corporation
Langjahr David
LandOfFree
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