The CPU time equation is as follows CPI means Clock cycles p

The CPU time equation is as follows, CPI means Clock cycles per instruction:
CPU Time = (Instructions/Program) * (CPI)*(Seconds/Clock cycle).

a. For each of the three factors in the CPU Time equation, answer the following questions:
(1) Can loop unrolling ALONE improve this factor, worsen this factor, or cannot affect this factor?
(2) If loop unrolling either improves or worsens the factor, how does this occur?

b. Once a loop has been unrolled, which factor(s) of the CPU Time equation can be improved, worsened, or cannot be affected through the application of instruction scheduling? Explain.

Solution

a)

1)

loop unrolling either improves or worse the instructions.

loop unrolling improves CPI

loop unrolling worse the clock cycle.

2)

insructions:

loop unrolling is to increase a program\'s speed by reducing or eliminating instructions that control the loop

unrolling of very large loops, can lead to increased code size.

so loop unrolling depends on code.

CPI:

loop unrolling improves instruction-level parallelism so can reduce CPI.

Clock cycle:

loop unrolling increases the area of the progamand can have a negitive impact on clock cycle time.

b)

by the application of instruction scheduling it is used to improve instruction-level parallelism

so it improves CPI(Clock cycles per instruction).