In an enhancement of a design of a CPU, the speed of a floating point unit has…
2004
In an enhancement of a design of a CPU, the speed of a floating point unit has been increased by 20% and the speed of a fixed point unit has been increased by 10%. What is the overall speedup achieved if the ratio of the number of floating point operations to the number of fixed point operations is 2:3 and the floating point operation used to take twice the time taken by the fixed point operation in the original design?
Answer: A. 1.155 — Solution: Let the original fixed-point operation time be f. Then the original floating-point operation time is 2f. Original total time for 2 floating and 3…
- A.
1.155
- B.
1.185
- C.
1.255
- D.
1.285
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Correct answer: A
Solution:
Let the original fixed-point operation time be f. Then the original floating-point operation time is 2f.
Original total time for 2 floating and 3 fixed operations: 2·(2f) + 3·(f) = 7f.
After improvements, floating-point time becomes 2f / 1.2 = 5/3·f and fixed-point time becomes f / 1.1 = 10/11·f.
New total time: 2·(5/3·f) + 3·(10/11·f) = (10/3 + 30/11)·f = 200/33·f.
Overall speedup = original total / new total = 7f / (200/33·f) = 231/200 = 1.155.
Therefore the overall speedup is approximately 1.155.
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