Question

Assume a program requires the execution of 50 x 106 FP instructions, 110 x 106 INT instructions, 80 x 106 L/S instructions, and 16 x 106 branch instructions. The CPI for each type of instruction is 1 1, 4, and 2, respectively. Assume that the processor has a 2 GHz clock rate 1.141 [10] <$1.10 By how much must we improve the CPI of FP instructions if we want the program to run two times faster? 1.14.2 [10]

Answer 1

Explanation:

FP - $50 \times 10^6$

CPI - 1

INT -$110 \times 10^6$,

CPI - 1

I/S - $80 \times 10^6$ ,

CPI - 4

Branch - $16 \times 10^6$

CPI - 2

Clock Speed - $2 \times 10^9$

Time(old) =$\frac{50 x 10^6 + 110 x 10^6 + 4 x ( 80 x 10^6) + 2 x (16 x 10^ 6)}{2 x 10^9}$

Time(old) = $256 \times 10^ {-3}$

Time(new) =  $\frac{256 \times 10^{-3}}{2}$

                = $128 \times 10^{-3}$

                =$\frac{CPI(new) x [50 x 10^6 + 110 x 10^6 + 4 x ( 80 x 10^6) + 2 x (16 x 10^ 6)]}{2 x 10^9}$

                =  $128 \times 10^{-3}$

CPI(new) = $\frac{-206}{50}$

               = -4.12