Electrical computers and digital processing systems: memory – Address formation – Generating prefetch – look-ahead – jump – or predictive address
Reexamination Certificate
1999-03-16
2001-08-14
Kim, Kenneth S. (Department: 2183)
Electrical computers and digital processing systems: memory
Address formation
Generating prefetch, look-ahead, jump, or predictive address
C711S137000, C712S207000, C712S225000
Reexamination Certificate
active
06275918
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates in general to data processing or information handling systems and, in particular, to a method and system for fetching data from memory. Still more particularly, the present invention relates to a method and system for pre-fetching data from memory based upon a pre-fetch history table.
2. Description of the Related Art
As processor clock frequencies have continued to increase, thereby permitting increased instruction throughput, memory latency has become a principal impediment to improved processor performance. Although instructions are commonly speculatively fetched from memory in order to ameliorate the effects of instruction access latency, in a conventional processor data is fetched from memory only after a load instruction has been executed to determine the address of the data to be fetched (i.e., only demand fetching is used).
The present invention includes a recognition that in order to reduce data access latency, it is desirable to intelligently pre-fetch data from memory. Modern microprocessors employ pre-fetching in order to reduce the latency involved in cache misses. An improved pre-fetching mechanism is needed to more accurately determine that a pre-fetch is likely to be useful as well as the best target to pre-fetch. The subject invention herein solves this problem in a new and unique manner that has not been part of the art previously.
SUMMARY OF THE INVENTION
It is therefore one object of the present invention to provide an improved method and system for data processing.
It is another object of the present invention to provide an improved method and system for fetching data from memory.
It is yet another object of the present invention to provide a processor and method for pre-fetching data from memory based upon a pre-fetch history table.
The foregoing objects are achieved as is now described. A method and system for improving pre-fetch accuracy in a data processing system or information handling system utilizing a pre-fetch history table compares a portion of an instruction address to an address located as an entry in a pre-fetch history table based on the status of a validity bit contained in the entry. If the validity bit is set and the addresses match, an indicator field within the entry is checked to see if it is equal to or greater than a threshold level. When the indicator field is greater than the threshold level, a target operand address is pre-fetched based on stride and direction.
The above as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed written description.
REFERENCES:
patent: 4764861 (1988-08-01), Shibuya
patent: 4984154 (1991-01-01), Hanatani et al.
patent: 5265213 (1993-11-01), Weiser et al.
patent: 5317702 (1994-05-01), Morisada
patent: 5377336 (1994-12-01), Eickemeyer et al.
patent: 5394530 (1995-02-01), Kitta
patent: 5404467 (1995-04-01), Saba et al.
patent: 5434985 (1995-07-01), Emma et al.
patent: 5623614 (1997-04-01), Van Dyke et al.
patent: 5790823 (1998-08-01), Puzak et al.
patent: 5822788 (1998-10-01), Kahn et al.
Burky William Elton
Lenk Peter Steven
Nguyen Dung Quoc
Schroter David Andrew
Tung Shih-Hsiung Stephen
Bracewell & Patterson L.L.P.
England Anthony V. S.
International Business Machines - Corporation
Kim Kenneth S.
LandOfFree
Obtaining load target operand pre-fetch address from history... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Obtaining load target operand pre-fetch address from history..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Obtaining load target operand pre-fetch address from history... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2546605