Lecture Notes for Computer Architecture II - St. Cloud State University

Question 4
Assuming the CPI for program 2 on each machine in Question 2.1 is the same as the
CPI for program 1 found in Question 2.3, find the instruction count for program 2
running on each machine using the execution times from Question 2.1.
Progra
m
Time on
M1
Time on
M2
1 10 seconds 5 seconds
2 3 seconds 4 seconds
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Given number of cycles per second & number of seconds can calculate number of
required cycles for each machine, then divide by CPI to get number of instruction.
Solution
Instructions per program
M1 3*200*10 9
10
Instructions per program
M2 4*300*10 9
9.4
Question 5
From 2.4
M1 = 60 GIPS
M2 = 127GIPS
M2 is twice as fast as M1
Does not cost twice
Question 6
Suppose you had many more machines to consider besides M1 and M2 described in
Questions 2.1 and 2.5 (each with a cost and an execution time for program 1, which you
need to run a large number of times). Could you use the cost divided by the execution
time as a metric to help you in your purchasing decision? How about the cost multiplied
by the execution time?
a. Cost * Execution time
b. Cost/Execution time
Solution
Use (a) Cost * Execution time
10,000*10 = 100,000
15,000*5 = 75,000
Cost/Execution time = cost * performance. Need performance for dollar value.