Please answer allquestions and show work. (Intro to Computer Architecture.) Refe
ID: 3864780 • Letter: P
Question
Please answer allquestions and show work. (Intro to Computer Architecture.)
Refer to the following table for the data required.
Arith
Store
Load
Branch
Instructions for a program
500
50
100
100
CPI
1
5
5
2
A.) Calculate execution time of a program on a 2 GHz processor.
B.) Find global CPI of the program.
C.) If number of load instructions can be reduced by one-half, what is the speed up and CPI?
D.) If number of store and arithmetic instructions can be reduced by one-half, what is the speed up
and CPI?
Arith
Store
Load
Branch
Instructions for a program
500
50
100
100
CPI
1
5
5
2
Explanation / Answer
A.) using the formula,
CPU time = (Instruction count x CPI) / clock rate
Arith: CPU Time = (500 x 1) / 2 x 109 = .00000025s
Store: CPU Time = (50 x 5) / 2 x 109 = .000000125s
Load: CPU Time = (100 x 5) / 2 x 109 = .00000025s
Branch: CPU Time = (100 x 2) / 2 x 109 = .0000001s
Thus, Execution Time = .00000025s + 0.000000125s + .00000025s + .0000001s = .000000725s = 725 x 10-9s
B.) Percentage of instructions for Arith, Store, Load, Branch : 67%, 7%, 13%, 13%
TCPI = (0.67 x 106 x 1) / 2 + (0.07 x 106 x 5) / 2 + (0.13 x 106 x 5) / 2 + (0.13 x 106 x 2) / 2
= (1.93 x 106) / 2
Global CPI = 1.93
C.) Load instructions are reduced by half, hence, number of Load instructions = 50
Execution Time = .00000025s + 0.000000125s + .000000125s + .0000001s = .0000006s = 600 x 10-9s
Speed Up = Execution time when load is 100 / Execution time when load is 50
= (725 x 10-9) / (600 x 10-9) = 1.21
New instructions percentage for arith, store, load, branch: 72%, 7%, 7% , 14%
New Load CPI = 0.07 x 5 = 0.35
TCPI = (0.72 x 106 x 1) / 2 + (0.07 x 106 x 5) / 2 + (0.07 x 106 x 5) / 2 + (0.14 x 106 x 2) / 2
= (1.7 x 106) / 2
Global CPI = 1.7
D.) Arith instructions are reduced by half, hence, number of Arith instructions = 250
Store instructions are reduced by half, hence, number of Store instructions = 25
Execution Time = .000000125s + .0000000625s + .00000025s + .0000001s = .0000006s = 537.5 x 10-9s
Speed Up = Execution time when arith is 500 and store is 50 / Execution time when arith is 250 and store is 25
= (725 x 10-9) / (537.5 x 10-9) = 1.35
New instructions percentage for arith, store, load, branch: 53%, 5%, 21% , 21%
New Arith CPI = 0.53 x 1 = 0.53
New Store CPI = 0.05 x 5 = 0.25
TCPI = (0.53 x 106 x 1) / 2 + (0.05 x 106 x 5) / 2 + (0.21 x 106 x 5) / 2 + (0.21 x 106 x 2) / 2
= (2.25 x 106) / 2
Global CPI = 2.25