Browse Prior Art Database

Branch Target Table

IP.com Disclosure Number: IPCOM000060548D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Emma, PG: AUTHOR [+5]

Abstract

This article describes a method of reducing idle time in Pipeline Processors by eliminating most of the branch instruction processing delay. For processors with sufficient cache bandwidth to do multiple I- Fetches, Operand Fetches per cycle, their ability to reduce taken branch delay is limited to the slight improvement they can achieve over a Decode History Table machine. The critical need in such a processor is to anticipate the taken branch much like the anticipation of the taken branches as achieved by a Branch History Table (BHT). The critical difference is that in such a dual stream environment it is not essential to know if the branch is taken so much as to know the target address of the branch instruction.

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Branch Target Table

This article describes a method of reducing idle time in Pipeline Processors by eliminating most of the branch instruction processing delay. For processors with sufficient cache bandwidth to do multiple I- Fetches, Operand Fetches per cycle, their ability to reduce taken branch delay is limited to the slight improvement they can achieve over a Decode History Table machine. The critical need in such a processor is to anticipate the taken branch much like the anticipation of the taken branches as achieved by a Branch History Table (BHT). The critical difference is that in such a dual stream environment it is not essential to know if the branch is taken so much as to know the target address of the branch instruction. A table of branch targets (BTT), which direct the alternate stream to those instructions which might be executed, establishes an advantage uniquely applicable to such a machine. The maintenance of this table is simplified in that only the target address must be correct and the conditionality of the branch simplifies dual streaming.

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