Touch history table

Details Touch history table Touch history table

1996-02-12

2000-04-25

Maung, Zarni

Electrical computers and digital processing systems: processing

Instruction fetching

Prefetching

712237, 712240, G06F 938

Patent

active

060556218

ABSTRACT:
A mechanism is described that predicts the success or failure of prefetching instructions based on the previous performance of the instructions. A prefetching instruction is successful if the block of information prefetched into the cache is used by the processor before it is discarded from the cache. A prefetching instruction is unsuccessful, a failure, if the block of information prefetched into the cache is not used while in the cache. The prediction regarding the success or failure of the prefetching instruction is performed utilizing a table that records the history regarding the usefulness of each prefetch made by a prefetching instruction at a given memory location. The table is called a Touch-History-Table (THT). The THT is preferably accessed during the decode phase of each instruction using the memory location of the instruction. The table records the history of previous outcomes (success or failure) of the prefetching instruction up to the table size. If a prefetch instruction is predicted as successful then a prefetch will occur and if a prefetch instruction is predicted as unsuccessful then no prefetch will be attempted.

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