Name Student # 4. (20%) Performance Consider a program with four classes of inst

Question

Name Student # 4. (20%) Performance Consider a program with four classes of instructions A, B, C and D. Refer to following table for the data. CPI % of instructions | 30% 1) Can we achieve a 2x overall speedup by only improving the CPI of instruction C? If so, please calculate the new CPI of the instruction C. Show all the steps Still based on the data shown in the table, can we achieve a 3x overall speedup by only improving the CPI of instruction C? If so, please calculate the new CPI of the instruction C. Show all the steps. 2)

Explanation / Answer

Hi,
Execution time = (CPI* number of instructions)/clock rate
CPI can be calulated as
(30 * 1) + (20 * 2) + (40 * 5)+(10 * 3)= 300/100= 3
so time t1= 3*N/C - let N and C be no of instructions and Clock rate
now if we want to achieve 2t1, CPI should become 6
i.e 6*100 = (30 * 1) + (20 * 2) + (40 * x)+(10 * 3)
x= 12.5, i.e CPI of C should be 20
b.To achieve 3x speed, CPI should be 9 i.e
i.e 9*100 = (30 * 1) + (20 * 2) + (40 * x)+(10 * 3)
x=20, i.e CPI of C should be 20
Thumbs up if this was helpful, othewise let me know in comments

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