Advanced Computer Architecture, Imperial
College 2001
11
index
bit n....1,0
Program counter
k low-order bits
0
1
2k
Branch history register
m bits
bit n....1,0
0
1
2k
prediction
bit n....1,0
0
1
2k
bit n....1,0
0
1
2k
Select
n-bit local branch history
2m n-bit BHTs
Popular choice is m=2, n=2, so four tables each of 2x2k bits
2
2
2
2