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Browse Prior Art Database

MSIS Branching Into OOS Z-code

IP.com Disclosure Number: IPCOM000103677D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 4 page(s) / 183K

Publishing Venue

IBM

Related People

Ekanadham, K: AUTHOR [+4]

Abstract

MSIS (Multisequencing a Single Instruction Stream) is a uniprocessor organization in which a set of processing elements (PEs) working in concert execute Segments of the instruction stream. The Segments are either P-Segments, normal uniprocessor instruction stream portions, that are processed in the E-MODE of MSIS and produce Z-Segments, or the Z-Segments that are processed in Z-MODE by MSIS. The main difference between E-MODE and Z-MODE is that during E-MODE each PE sees all instructions in the Segment and executes the ones that are assigned to it, but during Z-MODE, a PE only sees the instructions assigned to it.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 36% of the total text.

MSIS Branching Into OOS Z-code

       MSIS (Multisequencing a Single Instruction Stream) is a
uniprocessor organization in which a set of processing elements (PEs)
working in concert execute Segments of the instruction stream.  The
Segments are either P-Segments, normal uniprocessor instruction
stream portions, that are processed in the E-MODE of MSIS and produce
Z-Segments, or the Z-Segments that are processed in Z-MODE by MSIS.
The main difference between E-MODE and Z-MODE is that during E-MODE
each PE sees all instructions in the Segment and executes the ones
that are assigned to it, but during Z-MODE, a PE only sees the
instructions assigned to it.

      As all PEs see all instructions in E-MODE, each PE can create
the Z-CODE it will require to re-execute the Segment as a Z-Segment,
the Z-CODE being stored in the Z-CACHE, and associated with
instructions in the Z-CODE are S-LISTS and D-LISTS as appropriate.
An S-LIST instructs the PE, in the Z-MODE, that one or more of the
source registers in an instruction assigned to it is set by another
instruction that is executed on another PE, an S-LIST is a receiving
obligation.  The D-LIST instructs the PE in the Z-MODE as to the
names of PEs that require the values of the register(s) that are
being set by an instruction that is assigned to it.  A D-LIST entry
is a sending obligation.

      The set of instructions assigned to a single PE can be further
delineated as THREADS.  A THREAD is a sequence of instructions in the
original conceptual order and a Thread is associated with a register
file which is either real or virtual.  There are no sending or
receiving obligations between instructions within a THREAD and the
THREAD is the smallest unit of aggregation of instructions from a
SEGMENT.

      The requirement that instructions be scheduled in conceptual
sequence within a PE in MSIS can be overcome by virtualizing the name
of the Processor Elements and scheduling virtual PE in conceptual
sequence.  The instructions associated with a virtual PE is also
called a THREAD.

      With  the ability to used virtualized names for a given PE and
the concomitant reduction in schedules lengths (makespans), based on
the the loss on the requirement to maintain conceptual sequence
within physical PE, comes the problem of branching in the OOS Z-CODE.
By virtualizing the names of the PEs and creating PE-IDs or THREADS,
the resulting schedule sequence within a given PE may well be Out Of
conceptual Sequence (OOS).  The Z-CODE is called OOS Z-CODE.  The
problem of branching into OOS Z-CODE relates to the loss of the
property of a contour within the Z-CODE.  For each instruction I
within P-SEGMENT there is a position within the Z-CODE of all PEs
that represent the Z-SEGMENT such that no instruction that is
conceptually before I is found at that position or at a succeeding
position.  The set of such positions is called the contour of I.
This property clearly  relates to the maint...