Boots – shoes – and leggings
Patent
1989-10-30
1993-05-11
Lee, Thomas C.
Boots, shoes, and leggings
3642613, 3642615, 3642617, 3642646, 3649381, 3649382, 3642854, 364460, 364DIG1, 3649446, 371 51, 371 55, 395800, G06F 932, G06F 1134
Patent
active
052108317
ABSTRACT:
Methods and apparatus are described for processing branch instructions using a history based branch prediction mechanism (such as a branch history table) in combination with a data dependent branch table (DDBT), where the branch instructions can vary in both outcome and test operand location. The novel methods and apparatus are sensitive to branch mispredictions and to operand addresses used by the DDBT, to identify irrelevant DDBT entries. Irrelevant DDBT entries are identified within the prediction mechanism using state bits which, when set, indicate that: (1) a given entry in the prediction mechanism was updated by the DDBT and (2) subsequent to such update a misprediction occurred making further DDBT updates irrelevant. Once a DDBT entry is determined to be irrelevant, it is prevented from updating the prediction mechanism. The invention also provides methods and apparatus for locating and removing irrelevant entries from the DDBT. The update packet, sent by the DDBT to the history based prediction mechanism, is expanded to include the test operand address actually used by the DDBT. If the state bits indicate the update is irrelevant, then the operand address can be used to locate and delete the offending DDBT entry since the DDBT is organized based on operand addresses. Additionally, the invention provides for inhibiting creation of further DDBT entries when a Branch Wrong Guess event occurs subsequent to a DDBT update to a given prediction mechanism entry.
REFERENCES:
patent: 3559183 (1971-01-01), Sussenguth
patent: 4370711 (1983-01-01), Smith
patent: 4430706 (1984-02-01), Sand
patent: 4445216 (1984-04-01), Kobari et al.
patent: 4477872 (1984-10-01), Loss et al.
patent: 4710925 (1987-12-01), Negi
patent: 4763245 (1988-08-01), Emma et al.
patent: 4764861 (1988-08-01), Shibuya
patent: 4881170 (1989-11-01), Morisada
patent: 4939731 (1990-07-01), Reed et al.
patent: 4984154 (1991-01-01), Hanatani et al.
patent: 5031179 (1991-07-01), Yoshida et al.
patent: 5056092 (1991-10-01), Bruner
patent: 5058115 (1991-10-01), Blake et al.
"Comprehensive Branch Prediction Mechanism for BC", R. N. Rechtschaffen et al., IBM TDB, vol. 28, No. 5, Oct. 1985.
"Address Generate Interlock Avoidance for Branch Instructions in a Branch-History-Table Processor", G. C. Driscoll et al., IBM TDB, vol. 24, No. 1A, Jun. 1981.
"Preferred Block Encoding for Truncated BHT Entries", P. G. Emma et al., IBM TDB, vol. 28, No. 9, Feb. 1986.
Emma Philip G.
Knight Joshua W.
Pomerene James H.
Rechtschaffen Rudolph N.
Sparacio Frank J.
Drumheller Ronald L.
International Business Machines - Corporation
Kim Ken S.
Lee Thomas C.
LandOfFree
Methods and apparatus for insulating a branch prediction mechani does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods and apparatus for insulating a branch prediction mechani, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods and apparatus for insulating a branch prediction mechani will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1357320