Suppose you have a machine which takes 50% times to execute floating point multi

Question

Suppose you have a machine which takes 50% times to execute floating point multiply, which takes 20% time to execute floating point divide, and the remaining 30% are for other instructions. Management wants the machine to run 4 times faster. You can make the divide run at most 3 times faster and the multiply run at most 8 times faster. Suppose you have a machine which takes 50% times to execute floating point multiply, which takes 20% time to execute floating point divide, and the remaining 30% are for other instructions. Management wants the machine to run 4 times faster. You can make the divide run at most 3 times faster and the multiply run at most 8 times faster. Suppose you have a machine which takes 50% times to execute floating point multiply, which takes 20% time to execute floating point divide, and the remaining 30% are for other instructions. Management wants the machine to run 4 times faster. You can make the divide run at most 3 times faster and the multiply run at most 8 times faster.

Explanation / Answer

Amdahl's Law states:

Execution time after improvement = (Execution time affected by improvement)/(Amount of Improvement ) + Execution time unaffected

Assuming initially that the floating point multiply,floating point divide and the other instructions had the same CPI,
Execution time after Improvement with Divide = (20)/3 + (50+30) = 86.67

Execution time after improvement with Multiply = (50)/8 + (20 + 30) = 66.67

The mangement's goal can be met by making the improvement with Multiply alone

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