Browse Prior Art Database

USING BITS IN AN OPCODE TO SPECIFY WHAT TO INVALIDATE IN A CACHE

IP.com Disclosure Number: IPCOM000005630D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2001-Oct-22

Publishing Venue

Motorola

Related People

Authors:
Ralph McGarity Michael Cruess

Abstract

Thedesign of the MC68851 Paged Memory Management Unit contains an Address Translation Cache that stores recently used logical to physical address translations. For various reasons, the data that is stored in this cache can become out of date. An example is the fixing of a page fault by an operating system. The operating system brings the page of data from a disk to main memory, but the cache may still contain information in- dicating that the page is out on the disk. The old information must be removed from the cache. One way of guaranteeing that the old information is removed from the cache is to invalidate all of entries in the cache. Due to the large size of the cache in the MC68851, we decided that it would cost too much in terms of time to refill the entire cache when all that was required was the removal of one entry.