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:
Mar. 01, 1994
Filed:
Oct. 31, 1990
Philip G Emma, Danbury, CT (US);
Joshua W Knight, Mohegan Lake, NY (US);
Kevin P McAuliffe, Peekskill, NY (US);
James H Pomerene, Chappaqua, NY (US);
Rudolph N Rechtschaffen, Scarsdale, NY (US);
Frank J Sparacio, Sarasota, FL (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
A system is provided for management of data in cache memories in a multiprocessor environment which allows portions of lines to be valid and exclusive, while other portions are valid, but not exclusive, or invalid. A processor may store into portions of a line under its exclusive control without invalidating copies of the line held in the cache memories of the other processors. The system includes at least two processors, a shared main memory and a system control element, and each processor has a corresponding cache memory, a modified line stack and a sectored line directory. The modified line stack identifies data lines which have been changed since being made resident in cache memory. It also identifies the status of change of each word within those lines. A 'shared exclusive' flag in the system control element identifies each line for which portions of the line are under exclusive control of more than one processor. The sectored line directory identifies the control status and change status of individual words within a line flagged as 'shared exclusive.' If a line is shared exclusive, an entry for that line is recorded in the sectored line directory. For those lines with entries in the sectored line directory, a processor may store into words within its exclusive control, and fetch words within its exclusive or read-only control. Remote processors may fetch words which are held read-only by the local processor, and store into words which are marked invalid in the cache memory of the local processor.