Question

Two processors, P1 and P2, execute the same instructions. The clock rate and CPIs are as specified below:

Processor                 P1             P2

Clock Rate              2 GHz        3 GHz

CPI                          1.0     2.5

For processor P2, we are trying to reduce the time by 40% but this leads to an increase of 20% in CPI.

What clock rate is required to achieve this time reduction?

Answer 1

`Hey,

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Execution time = (Num of instructions * CPI) / (Clock rate)

So if we want to reduce the execution time by 40%, and CPI increases by 20%, we

have:

Execution time * 0.6 = (Num of instructions * CPI * 1.2) / (New Clock rate)

New Clock rate = Clock rate * 1.2 / 0.6 = 2 * Clock rate

New Clock rate for each processor:

P1: 2GHz * 2 = 4 GHz

P2: 3GHz * 2 = 6 GHz

Kindly revert for any queries

Thanks.