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Browse Prior Art Database

Processor with Non-snoop and Snoop Data Caches

IP.com Disclosure Number: IPCOM000109342D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Kawase, K: AUTHOR [+3]

Abstract

Disclosed is a processor which has both non-snoop cache and snoop cache for use in a tightly coupled shared memory multiprocessor system.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 68% of the total text.

Processor with Non-snoop and Snoop Data Caches

       Disclosed is a processor which has both non-snoop cache
and snoop cache for use in a tightly coupled shared memory
multiprocessor system.

      In a tightly coupled shared memory multi-processor system,
snoop cache scheme is often used to maintain cache coherency.  To
implement this, costly dual-port memory chips are required for cache
tag memory, since a snoop cache controller has to process both cache
access from a main processor and shared memory bus transactions
simultaneously.

      Data contained in shared memory are not always required to be
stored to snoop cache.  For example, a variable which is statically
analyzed as local to a processor, which means that the other
processors never access the variable, can be safely stored in
non-snoop cache.  Read-only data which is calculated before can also
be stored in non- snoop cache.  When two or more processors access
and modify the same data, if ordering of data access by processors
are analyzed statically, the data can be stored in a non-snoop cache
by inserting explicit cache control operation before and after data
accesses.  Thus, all caches need not to be snoop cache.  By using
both non-snoop cache and snoop cache properly, the total system cost
will be reduced.

      Having both a non-snoop and snoop cache system takes advantage
of multi-level cache multi-processor system.  For non-snoop cache,
inclusion property does not need to be form...