2. (10 points) Suppose you have a load/store computer as described above with th

Question

2. (10 points) Suppose you have a load/store computer as described above with the following instruction mix: o.of Clock cycles per ALU ops Loads Stores Branches 35% 25% 15% 25% (a) Compute the CPI. Show all your work. (b) We observe that 25% of the ALU ops are paired with a load, and we propose to replace these ALU ops and their loads with a new instruction. The new instruction takes l clock cycle. With the new instruction added, branches take 5 clock cycles. Compute the CPI for the new version. Show all your work. (c) If the clock rate for the new version is 30% faster than the old version, which version is faster and by what percent? Justify your answer quantitatively by comparing expressions for CPU Execution time. Show all your work.

Explanation / Answer

CPI = (F1*C1 + F2*C2 + ... + Fc*Cn)

old CPI = (35*1 + 25*2 + 15*2 + 25*3)

= 35 + 50 + 30 + 75

= 185

new CPI = 35*1 + 25*1 + 25*5

= 35 + 25 + 125

= 185

The clock rate of both the versions are same

If clock rate of new version is faster is than that of old version, then the newer version will be faster as for now less number of cycles will be needed for instruction to execute hence speeding up the process

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