Methods and apparatuses for servicing load instructions
US5745729A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 16, 1995 |
| Grant date | Apr 28, 1998 |
| Priority date | — |
| Expiry date | Feb 16, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F12/0859
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
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. A method and apparatus al…
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