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Browse Prior Art Database

Computer Cache System With Priority Retention of Data Over Instructions

IP.com Disclosure Number: IPCOM000043832D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Giraud, F: AUTHOR [+9]

Abstract

The speed and efficiency of operation of a cache buffer memory for fetching instructions and data from the main memory for use by the processor in a computer system has been greatly increased by pre-fetching instructions into the cache based upon predictable needs for those instructions during the execution of a program. In accordance with the present invention, it has been determined that a further substantial increase in efficiency is achievable by providing more space in the cache for data than for instructions. The present invention relates to a cache system in which instructions and data are stored in the same cache, and in which "least recently used" items are dropped out of the cache when new items are fetched to the cache from the main memory for use by the processor.

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Computer Cache System With Priority Retention of Data Over Instructions

The speed and efficiency of operation of a cache buffer memory for fetching instructions and data from the main memory for use by the processor in a computer system has been greatly increased by pre-fetching instructions into the cache based upon predictable needs for those instructions during the execution of a program. In accordance with the present invention, it has been determined that a further substantial increase in efficiency is achievable by providing more space in the cache for data than for instructions. The present invention relates to a cache system in which instructions and data are stored in the same cache, and in which "least recently used" items are dropped out of the cache when new items are fetched to the cache from the main memory for use by the processor. It has been determined that a substantial improvement in efficiency in the operation of such a cache with respect to instruction items is available by pre-fetching instruction items to the cache for a program which is being processed. This improvement in efficiency may be in the order of 70%, in terms of a reduction in the frequency with which "misses" are encountered, such that new instructions must be fetched from main memory. If the calls for data items and instruction items are approximately equal, this represents an approximate 35% improvement in operation of the cache by pre-fetching instructions. Since there is generally no clear basis for pre-fetching data, improvements in efficiency by pre-fetching are not available for data. However, in accordance with the present invention, it has been determined that the efficiency can be increased by approximately an additional 6% by all...