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:
Dec. 11, 1990
Filed:
Apr. 01, 1988
Joseph Rastegar, Newton, MA (US);
Anne S Valiton, Westboro, MA (US);
Digital Equipment Corporation, Maynard, MA (US);
Abstract
This invention is directed to a memory system that determines which blocks of a set of associative blocks in cache memory are unavailable for replacement. This is accomplished by operating the memory system to maintain a duplicate set of tags which track block ownership for this cache pursuant to a 'snoopy' protocol. In addition, the cache system maintains a bit associated with each memory address to indicate whether any data blocks resident in it have been locked. The interlock status of the data blocks in the cache is not communicated to the memory system. Once a block is locked, it cannot be allocated for replacement until it is unlocked. When the cache system encounters a locked block, it skips over that block and allocates the next block of the associative blocks. From this, the memory system infers, by means of a replacement algorithm, that block is being locked and, therefore, cannot be replaced. This enables the memory system to implement an irregular replacement policy for this cache when the block to be replaced is owned and locked.