Browse Prior Art Database

Branch Resolution in the Cache

IP.com Disclosure Number: IPCOM000099281D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 1 page(s) / 53K

Publishing Venue

IBM

Related People

Emma, PG: AUTHOR [+5]

Abstract

A processor can forward a TM/BC pair to the cache that the cache can restart the correct instruction stream the case of a branch wrong guess (BWG). Such an approach beneficial for processor designs with long pipelines and cache access times.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 72% of the total text.

Branch Resolution in the Cache

       A processor can forward a TM/BC pair to the cache that the
cache can restart the correct instruction stream the case of a branch
wrong guess (BWG).  Such an approach beneficial for processor designs
with long pipelines and cache access times.

      The duration of pipeline disruptions that delay a increases as
the cache access time increases.  In the delay associated with a
conditional branch has been guessed wrong (BWG) by a Branch History
Table will increase by two cycles for each cycle of increase the
cache access time.  One cycle is in the DWS (Decoding Stream)
interval and the other is in the restart or (Instruction Buffer
Empty) interval, i.e., the time to the new instruction stream.  In
processors, the cache access interval is of three sub-intervals:
1.  The period prior to the cache access.
2.  The cache access time per se .
3.  The period following the completion of the cache access.

      The first and third periods are used to transmit the and the
results of this request to and from the respectively.  Such
sub-intervals are recoverable if cache rather than the processor
(requester) can utilize result of the cache access and act
appropriately.

      The basic idea is to transmit sufficient information a
conditional branch, typified as a TM/BC pair, so the cache can
resolve the branch and avoid the delay by the transmission intervals.
 A more detailed of the pipeline indicates the superiority of thi...