1. Consider two different implementations, M1and M2, of the same instruction set

Question

1. Consider two different implementations, M1and M2, of the same instruction set. There are three classes ofinstructions (A, B, and C) in the instruction set. M1 has a clockrate of 80 MHz and M2 has a clock rate of 100 MHz. The averagenumber of cycles for each instruction class and their frequencies(for a typical program) are as follows:on

               B          2             3             30%

               C         4             4             10%

(a) Calculate the average CPI for eachmachine, M1, and M2.

(b) Calculate the average MIPS ratings foreach machine, M1 and M2.

(c) Which machine has a smaller MIPS rating ?Which individual instruction class CPI do you needto

change, and by how much, to have this machinehave the same or better performance as themachine

with the higher MIPS rating (you can onlychange the CPI for one of the instruction classes onthe

slower machine)?

Explanation / Answer

c)    Machine M2 has a smaller MIPS rating Changing instruction set A from 2 to 1 The CPI will be increased to 1.9 (1*.6+3*.3+4*.1) and hence MIPS Rating will now be (100/1.9)*10^6 =52.6*10^6.

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