1. For a typical workload, the percentages of three groups of instructions and their average
CPI are given in the following table.
Instruction Percentage CPI
Integer 50 1
Load/Store 30 3
Floating-point 20 10
There are two possible ways to make performance improvement. First, an enhanced
compiler can reduce the floating-point instructions to ½ of the original floating-point
instructions with the cost of increasing the integer instructions by 30% of the original
integer instructions. Second, a new pipeline technique can reduce the average CPI of the
floating-point instruction from 10 to 5 without increasing the clock cycle time. Compare the
performance improvement of the two solutions. Calculate which solution is better and by
how much.
Answer:
First enhancement:
Percentage Adjusted % CPI
Integer 50*(1+30%)=65 65/105=61.9 1
Load/Store 30 30/105=28.6 3
Floating P 20*1/2 = 10 10/105=9.5 10
CPI = 61.9%*1 + 28.6%*3 + 9.5%*10 = 2.427
Second enhancement:
CPI = 50%*1 +30%*3 + 20%*5 = 2.4
.
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