Two machines are under consideration: M1 and M1. The table below lists the clock

Question

Two machines are under consideration: M1 and M1. The table below lists the clock periods for each machine, as well as the instruction mix for a program that approximates the average use of students in the lab. Answer the following questions A) A new machine, M3, is being considered to replace the lab machines. M3's design is based on M2. The only difference is that M3 will execute MULT instructions 5 times faster than M2. what is the speedup of M3 as compared to M2? B) Which machine should we adopt: M1, M2, or M3?

Explanation / Answer

Answer:

A). CPI(clock per instruction ) of M3=0.25*3+0.25*3+0.15*5+0.15*5+0.1*3+0.1*1=3.4 because the cycles for MULT will be 1 in case of M3

So speed up=3.8/3.4=1.117

B).

Performance = 1 / Execution Time

Execution time of M1 is higher than M2 so the permonce of M2 is better than M1

And Execution time= instruction count*clock rate*CPI

Instruction count and clock rate will be same in M3 and M2 But CPI of M2 is higher than CPI of M3 so the execution time will be higher in case M2 compare to M3.

So performance of M3 will be highest among all three machines.

Hence we will adopt the M3

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