1. Branch Predictor Animations
Bimodal, Local, Global
CS 450/650, ECE 621
Andrew Morton

2. Code Example line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8 9 T line i j b1 b23 6 4 NT 5 7 2 8 9 T
line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8 9 T
line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8 9 T
line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8 9 T
line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8 9 T
line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8 9 T
line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8
line i j b1 b2 b3 1 3 6 4 NT 5 7 2
line i j b1 b2 b3 1 3
line i j b1 b2 b3 1 3 6
line i j b1 b2 b3 1 3 6 4 NT
line i j b1 b2 b3 1 3 6 4 NT 5
line i j b1 b2 b3 1 3 6 4 NT 5
1 int i=0, j=3; 2 do { 3 j += 3; 4 b1: if(i == 0) 5 j %= 5; 6 b2: if(j < 2) 7 j++; 8 i++; 9 b3: } while(i<2);

3. Bimodal Predictor (b2) individual 2-bit up/down counter counters xx PC
line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8 9 T
individual 2-bit up/down counter
initial state = 10
counters xx PC 10 01 10 xx xx

4. Local Predictor (b2) shared 2-bit up/down counters
line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8 9 T
shared 2-bit up/down counters
initial states = 10
individual local histories
initialized to 11
local histories
counters xx 10 PC 11 01 10 10 xx 11 10 xx 10 01

5. Global Predictor (b1,b2,b3)
line i j b1 b2 b3 1 3 6 4 NT 5 7 2 8 9 T
shared 2-bit up/down counters
initial states = 10
one global history
initialized to 11
counters
global history 11 10 PC 11 01 00 10 10 10 01 10 01