Electrical computers and digital processing systems: memory – Storage accessing and control – Hierarchical memories
Patent
1997-10-07
1998-09-01
Chan, Eddie P.
Electrical computers and digital processing systems: memory
Storage accessing and control
Hierarchical memories
711140, 711131, G06F 1200
Patent
active
058025758
ABSTRACT:
A dual-ported tag array of a cache allows simultaneous access of the tag array by miss data of older LOAD instructions being returned during the same cycle that a new LOAD instruction is accessing the tag array to check for a cache hit. Because a load buffer queues LOAD instructions, the cache tags for older LOAD instructions which missed the cache return later when new LOAD instructions are accessing a tag array to check for cache hits. A method and apparatus for calculating and maintaining a hit bit in a load buffer perform the determination of whether or not a newly dispatched LOAD will hit the cache after it has been queued into the load buffer and waited for all older LOADs to be processed. A load buffer data entry includes the hit bit and all information necessary to process the LOAD instruction and calculate the hit bits for future LOAD instructions which must be buffered. A method and apparatus for servicing LOAD instructions, in which the access of the data array portion of a cache and the tag array portion are decoupled, allows the delayed access of the data array after a LOAD has been delayed in the load buffer without reaccessing the tag array.
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Greenley Dale
Kohn Leslie
Williams Greg
Yeh Ming
Chan Eddie P.
Sun Microsystems Inc.
Verbrugge Kevin
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