Solution (A)
The formula to calculate the execution time : Execution Time = IC CPI T
IC for Load / Store Instructions
IC for ALU instructions
IC for Control instructions
= Total Instructions Ratio of Load / Store Instructions = 200 0.35
= 70 instructions
= Total Instructions Ratio of ALU Instructions = 200 0.55
= 110 instructions
= Total Instructions Ratio of Control Instructions = 200 0.10
= 20 instructions
Now, we will calculate the total clock cycles required to execute each type of instructions
Total Clock Cycles for Load / Store
Total Clock Cycles for ALU
Total Clock Cycles for Control
= IC for Load / Store CPI for Load / Store = 70 2.5
= 175 clock cycles
= IC for ALU CPI for ALU = 110 1.25
= 137.5 clock cycles
= IC for control CPI for control = 20 3
= 60 clock cycles
Time required (in seconds) for each clock cycle (T)=1/CPU frequency 1 / 500 106 = 0.002 10−6 seconds
= 210−9 seconds
Now finally, we will calculate the execution time
Execution Time (ET ) = Total Clock Cycles 1/ CPU Frequency
= (175 + 137.5 + 60) (1/ 500 106 ) seconds
= 372.5210−9seconds 1/500106 =210−9seconds = 745 10−9 seconds
= 745 nanoseconds
Solution (B)
If decrease the average CPI for ALU by 20%, the new average CPI
New CPI for ALU = 1.25 (100−20)/100 = 1.25 0.8
= 1 CPI
If average CPI for Load / Store instruction is increased by 10%, new average CPI New CPI for Load / Store = 2.5 (100 +10)/100
= 2.5 1.1 = 2.75 CPI
Hence, new execution time will be
ExecutionTime(E.T) = (702.75+1101+203)x(1/500106)seconds
= (192.5+110+60)/(5108)seconds
= 362.5 2 10−9 seconds = 725 10−9 seconds
= 725 nanoseconds
Q. 2 Solution:
Solution A (0-Address Code)
PUSH B
PUSH C
ADD ; gives B+C PUSH A
MUL ; gives A(B+C) PUSH 2
PUSH A
MUL ; gives 2A PUSH C
MUL ; gives 2AC
PUSH B
DIV ; gives 2AC/B
SUB ; gives A(B+C) - 2AC/B
PUSH C
PUSH C
MUL ; gives C2
ADD ; gives POP D
A(B+C) - 2AC/B + C2
Solution A (1-Address Code)
LDA C MULA C STA X
LDA A MULA C MULA 2
; loads the value stored at memory location C in Accumulator ; gives C2
; stores C2 at memory location X
; loads the value stored at memory location A in Accumulator ; gives AC
; gives 2AC
DIVA B ADDA X STA Y
LDA B ADDA C MULA A SUB Y STA D
; gives 2AC/B
; adding 2AC/B with C2 stored in X gives 2AC/B + C2 ; stores 2AC/B + C2 at memory location Y
; loads the value stored at memory location B in Accumulator ; gives (B+C)
; gives A(B+C)
; subtracts 2AC/B + C2 from A(B+C)
; stores the result at memory location D
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