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:
May. 28, 1991
Filed:
Aug. 21, 1989
Brian Lefsky, West Newton, MA (US);
Mary E Natusch, Westford, MA (US);
Prime Computer, Inc., Natick, MA (US);
Abstract
A high availability set associative cache memory for use as a buffer between a main memory and a central processing unit includes multiple sets of cache cells contained in two or more cache memory elements. Each of the cache cells includes a data field, a tag field and a status field. The status field includes a force bit which indicates a defective cache cell when it is set. Output from a cache cell is suppressed when its force bit is set. The defective cache cell is effectively mapped out so that data is not stored in it. As long as one cell in a set remains operational, the system can continue operation. The status field also includes an update bit which indicates the update status of the respective cache cell. Replacement selection logic examines the bit pattern in all the cache cells in a set and selects a cache cell to be replaced using a first-in first-out algorithm. The state of the update bit is changed each time the data in the respective cache cell is replaced unless the cache cell was modified on a previous store cycle.