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Average machine cycles per instruction and clock rate

A certain microprocessor requires either 2, 4, 8, 12, or 16 machine cycles to perform various operations. Seventeen and one-half (17.5.) percent of its instructions require 2 machine cycles, 12.5% require 4 machine cycles, 35% require 8 machine cycles, 20% require 12 machine cycles, and 15% require 16 machine cycles.

a. What is the average number of machine cycles per instruction for this microprocessor?
b. What is the clock rate (machine cycles per second) required for this microprocessor to be a "1 MIPS" processor?
c. Suppose this system requires an extra 16 machine cycles to retrieve an operand from memory. It has to go to memory 30% of the time. What is the average number of machine cycles per instruction for this microprocessor, including its memory fetch instructions?

Solution Preview

a. Average number of machine cycles per instruction for the microprocessor
= 17.5% * 2 + 12.5% * 4 + 35% * 8 + 20% * 12 + 15% * 16
= 0.175 * 2 + 0.125 * 4 + 0.35 * 8 + 0.20 ...

Solution Summary

Stepwise computations are shown.

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