Browse Prior Art Database

Operation of the Branch History Table within Specialized Processors

IP.com Disclosure Number: IPCOM000104289D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 55K

Publishing Venue

IBM

Related People

Pomerene, J: AUTHOR [+2]

Abstract

In the presence of a homogeneous workload wherein individual transactions can be processed via a higher level of pipelining involving specialized processors that process specific stages of the overall transactions in turn, one of the presumed advantages is the operation of the BHT, Branch History Table, within each specialized processor. One can not help but notice that the BHT advantage reflects the limited I-SPACE that is within the purview of such a processor. This initial advantage can be extended by noting specific causal relationships to branch wrong guesses and effects of initial status versus final status of the BHT. A table of First Branch Actions that monitor the first branch actions of all TYPE B branches, as described below, can be used to detect and override such status on entry versus status on exit issues.

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Operation of the Branch History Table within Specialized Processors

      In the presence of a homogeneous workload wherein individual
transactions can be processed via a higher level of pipelining
involving specialized processors that process specific stages of the
overall transactions in turn, one of the presumed advantages is the
operation of the BHT, Branch History Table, within each specialized
processor.  One can not help but notice that the BHT advantage
reflects the limited I-SPACE that is within the purview of such a
processor.  This initial advantage can be extended by noting specific
causal relationships to branch wrong guesses and effects of initial
status versus final status of the BHT.  A table of First Branch
Actions that monitor the first branch actions of all TYPE B branches,
as described below, can be used to detect and override such status on
entry versus status on exit issues.  Other sources of BWG can be
handled more easily by existing extensions to the BHT that concern
data dependencies.

      Two unique aspects of the operation of a BHT within a
specialized processor, something that can be determined by a mode bit
within the BHT, differentiates it from the normal action of a BHT in
a general framework:

o   A well defined interface exists with respect to a Processor
    Transition (PT) that determines an entry to a new execution
    phase.  Similarly a well defined interface exists which
    determines that the specialized proc...