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US006687794B2
(12) United States Patent (io) Patent No.: US 6,687,794 B2
Malik (45) Date of Patent: Feb. 3,2004
(54) PREFETCHING MECHANISM FOR DATA CACHES
(75) Inventor: Nadeem Malik, Austin, TX (US)
(73) Assignee: International Business Machines Corporation, Armonk, NY (US)
( * ) Notice: Subject to any disclaimer, the term ol this patent is extended or adjusted under 35 U.S.C. 154(b) by 290 days.
(21) Appl. No.: 09/981,874
(22) Filed: Oct. 18, 2001
(65) Prior Publication Data
US 2003/0079088 Al Apr. 24, 2003
(51) Int. CI.7 G06F 12/00
(52) U.S. CI 711/137; 711/144; 711/159;
711/204; 711/213
(58) Field of Search 711/137, 144,
711/159, 204, 213
(56) References Cited
U.S. PATENT DOCUMENTS
5,142,634 A * 8/1992 Fite et al 712/240
A data structure to aid in and a method, system, and computer program product for prefetching data from a data cache are provided. In one embodiment, the data structure includes a prediction history field, a next line address field, and a data field. The prediction history field provides information about the success of past data cache address predictions. The next line address field provides information about the predicted next data cache lines to be accessed. The data field provides data to be used by the processor. When a data line in the data cache is accessed by the processor, determines the value of a prediction history field and the value of a next line address field. If the prediction history field is true, then the next line address in the next line address field is prefetched. Based on whether the next line actually utilized by the processor matches the next line address in the next line address field, the contents of the prediction history field and the next line address filed are modified.
20 Claims, 3 Drawing Sheets
