GATE 2016 CS – Question 42
The stage delays in a 4-stage pipeline are 800, 500, 400 and 300 picoseconds. The first stage (with delay 800 picoseconds) is replaced with a functionally equivalent design involving two stages with respective delays 600 and 350 picoseconds. The throughput increase of the pipeline is ________ percent.
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Correct answer: 33 to 34
Explanation
A pipeline's clock period is set by its slowest stage. Before the change it is 800 ps. After the change the stages are 600, 350, 500, 400 and 300 ps, so the slowest is 600 ps. Throughput is the inverse of the period, so the increase is $\frac{800}{600} - 1 = 0.333$, which is about 33.3 percent.