Question

Question 15 Assume that an architecture uses 2-bit branch predictor and the predictor is initially set to WNT. For the following branch outcomes, indicate if each outcome is correctly predicted or not. In the table, T and NT represent Taken and Not-Taken branch outcomes, respectively. The states for 2-bit branch are ST (Strong-Taken), WT (Weak-Taken), WNT (Weak-Not-Taken), SNT (Strong-Not-Taken). Please use C for correct prediction and I for incorrect prediction. Branch Outcome T T T T T NT NT NT T T T T NT NT T CA

Answer 1

Initial state = WNT

Branch outcome = T
Prediction = NT
Incorrect(I)

Branch outcome = T
Prediction = T
correct(c)

Branch outcome = T
Prediction = T
correct(c)

Branch outcome = T
Prediction = T
correct(c)

Branch outcome = T
Prediction = T
correct(c)

Branch outcome = NT
Prediction = T
Incorrect(I)

Branch outcome = NT
Prediction = T
Incorrect(I)

Branch outcome = NT
Prediction = NT
correct(c)

Branch outcome = T
Prediction = NT
Incorrect(I)

Branch outcome = T
Prediction = T
correct(c)

Branch outcome = T
Prediction = T
correct(c)

Branch outcome = T
Prediction = T
correct(c)

Branch outcome = NT
Prediction = T
Incorrect(I)

Branch outcome = NT
Prediction = T
Incorrect(I)

Branch outcome = T
Prediction = NT
Incorrect(I)