1. (20 pts) Assume that a machine includes a floating point (FP) unit, which con
ID: 3590146 • Letter: 1
Question
1. (20 pts) Assume that a machine includes a floating point (FP) unit, which contains an FP square root (F PSQR) instruction. Suppose we have the following measurements. Frequency of FP operations = 20%. Frequency of FPSO-4% Average CPI of FP operations = 4.0. CPI of FPSO-20 Average CPI of other instructions (non-FP instructions) 1.4 a. What is the average CPI of the machine? b. If the average CPI of FP is decreased to 3, what is the average CPI of the new machine? c. If the CPI of FPSQR is decreased to 2, what is the average CPI of the new machine? d. Which design improvement is better of b and e?Explanation / Answer
a) Taking the weighted average we get:
0.2 * 4 + 0.04 * 20 + 0.76 * 1.4 = 2.66
average CPI for machine = 2.66
b) average CPI for FP is decreased to 3
0.3 * 0.2 + 0.04 * 20 + 0.76 * 1.4 = 2.46
average CPI for machine = 2.46
c) average CPI for FPSQR is decreased to 2
0.2 * 4 + 0.04 * 2 + 0.76 * 1.4 = 1.94
average CPI for machine = 1.94
d) c is better than b as we are getting better performance.
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