1. Branch Prediction

2. Literature Tse-Yu Yeh and Yale N. Patt, “A Comparison of Dynamic Branch Predictors that use Two Levels of Branch History,”Tse-Yu Yeh and Yale N. Patt, “A Comparison of Dynamic Branch Predictors that use Two Levels of Branch History,” Proceedings of the 20th annual international symposium on computer architecture, ISCA '93 –Also important: Reference 1,2,3 and 4 of this paper Tse-Yu Yeh and Yale N. Patt, “Tse-Yu Yeh and Yale N. Patt, “Two-level adaptive training branch prediction, “ Proceedings of the 24th annual international symposium on Microarchitecture

3. Two-Level Adaptive Branch Prediction First level, execution history register(s): History of the last k branches encountered.First level, execution history register(s): History of the last k branches encountered. Second level, pattern history table(s): k refers to a place in the pattern history table that contains the prediction based on the outcome of the branches at the last j occurences of k, Predictor is for instance a prediction counter.Second level, pattern history table(s): k refers to a place in the pattern history table that contains the prediction based on the outcome of the branches at the last j occurences of k, Predictor is for instance a prediction counter.

4. 1st Level Branch History Register or Table (BHR or BHT) Global History of all branches kept in a single register of length k.Global History of all branches kept in a single register of length k. Per-address Table that contains a history register of length k for each branch.Per-address Table that contains a history register of length k for each branch. Per Set Table that contains a history register of length k for each set of branches.Per Set Table that contains a history register of length k for each set of branches.

5. 2nd level Pattern History Table (PHT) global Table with a prediction for all possible values of k.global Table with a prediction for all possible values of k. per-address Table with a prediction for all possible values of k for each branch address.per-address Table with a prediction for all possible values of k for each branch address. Per set Table with a prediction for all possible values of k for each branch set.Per set Table with a prediction for all possible values of k for each branch set.

6. The 9 Variations of 2-Level Adaptive Branch prediction

7. Branch prediction is a very important factor in reducing CPI in modern processors that use extensive pipelining.Branch prediction is a very important factor in reducing CPI in modern processors that use extensive pipelining. A counter is often used for prediction (2 bit)A counter is often used for prediction (2 bit) Two-Level Adaptive Dynamic Branch Prediction ‘learns’ the outcome of branches in different program states.Two-Level Adaptive Dynamic Branch Prediction ‘learns’ the outcome of branches in different program states. 9 Variations of 2-L.A.B.P. (Global, Per-Address and Per-Set for both levels), but only 4 useful.9 Variations of 2-L.A.B.P. (Global, Per-Address and Per-Set for both levels), but only 4 useful.Summary