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:
Nov. 02, 1999
Filed:
Jan. 17, 1997
Julie W Moncton, Cupertino, CA (US);
Kenneth K Chan, Saratoga, CA (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
An apparatus and method for duplicating tag addresses to maintain addresses of central processing unit (CPU) data stored in write buffers external to a cache are disclosed. Advance notification of write transactions is issued to allow a subsystem that maintains duplicate cache tags to know in advance which write transactions are present in the CPU's buffers. Such information is used to keep duplicate tags for both the cache and any buffers that contain writes that are to be removed from the cache. The cache is preferably a direct mapped cache and the CPU preferably resides within a multiprocessor architecture. In the preferred embodiment, all write transactions are indirectly caused by a read transaction that is about to bring a line into the cache. Thus, a read transaction is issued by the CPU before the write transaction is issued. A field is added to the read transaction that indicates whether or not the read transaction has a corresponding line that must be written out of the cache and into a buffer, such that the duplicate tags duplicate both the CPU cache and the CPU write buffers.