The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 29, 1999
Filed:
Sep. 11, 1996
Thomas B Berg, Portland, OR (US);
Tapas Datta, Bangalore, IN;
Sequent Computer Systems, Inc., Beaverton, OR (US);
Abstract
In a digital computer with a cache comprised of N sets labeled 0 to N-1, cache tag memory for each set is divided into primary and mirror parts, each part with sufficient capacity to store a number of cache tags equal to the number of cache blocks storable in a cache memory associated with each set. Every modification or installation of cache tags in the primary part of a set x is accompanied or followed by identical modification or installation of cache tags in the mirror part of a set F(x), where F is a one-to-one function that maps the set of integers from 0 to N-1 onto itself. Cache tag lookup retrieves a first set of N cache tags from the primary part of each cache tag memory, and parity checking is performed on each tag. If a parity error is found, a set of cache tags is retrieved from the mirror part of the cache tag memories, and parity checking is again performed. If no error is found, cache processing proceeds normally. The cache tag memories are preferably SRAMs with a mirror enable bit driven by a cache controller such that tags are installed in or read from either a primary part or a mirror part of the SRAM depending on the value of the mirror enable bit.