Subject Computer Architecture

1. Suppose the following loop iterates 89 times. Assume a 1-bit predictor is used. Calculate the prediction accuracy of this predictor. Assume the buffer contains 0 initially.

1000     Loop:    fld f1, 0(x1)

1004                   ......

1008                   ......

1012                   bne x2, x0, -16

2. Answer Problem 3 using a 2-bit predictor. Assume the buffer contains 00 initially.

3. Consider the code in Example 4, Chapter 3 slides. Assume a ten entry Branch History Table of 2-bit predictor used with initial values of 01, 10, 10. Show the prediction behavior if the following are read into the code via a loop:

aa=2 and bb=3, followed by aa=2 and bb=2, followed by aa=4 and bb=2

Calculate the overall prediction accuracy.

4. a) Display a Branch Target Buffer for the code in Example 6. Assume 2- bits predictor for branches are initially 00, 10, 11.

b) Now assume you execute the code again and this time all three branches are taken. Display the new BTB.

5. State what takes place when each of the following instructions reach the top of ROB and their operands are all available:

a) fld         f2, 0(x6)

b) fadd      f2, f4, f6

c) fsd         f2, 0(x2)

d) addwi   x3, x3, #-8

e) bne       x3, x0, target (Mispredicted)

f) beq       x3, x0, Loop    (Predicted Correctly)