How do i calculate the average cpi?

Question

Im kinda stuck on some work. To find the the cpi i would need to multiply the percentage of instructions with the clock cycle but what is shown is avg stall cycles. I don't really understand how to approach this problem. Any help would be appreciated.

A computer with a 5 stage pipeline is measured and has the following characteristics 

Instruction Type % of instructions. Avg. stall cycles/instructions

Branches .3 .7 

Loads & Stores .2 .2  

ALU ops .4 0  

Other .1 .2 

a) what is the average CPI for the computer?

 b) What is the speedup for this machine?

So far I multiplied the percentage of instructions with avg stall cycles and then added them up, but don't think its right. .3 * .7 = .21 .2 * .2 = .04 .4 * 0 = 0 .1 * .2 = .02 .27 — user3562229, Apr 22 '14 at 23:04
You just put in some * and /, but is there any logic or reason to that? — MSalters, Apr 22 '14 at 23:08

score 0 · Answer 1 · answered Apr 23 '14 at 07:28

0

In your last comment, you have the correct weighted average of stall cycles per instruction. But you need the total cycles per instruction presumably.

As for speedup, it's unclear what your baseline is.

answered Apr 23 '14 at 07:28

MSalters

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How do i calculate the average cpi?

1 Answers1