A non-pipeline system takes 50ns to process a task. The same task can be…

2020

A non-pipeline system takes 50ns to process a task. The same task can be processed in six-segment pipeline with a clockcycle of 10ns. Determine approximately the speedup ratio of the pipeline for 500 tasks.

  1. A.

    6

  2. B.

    4.95

  3. C.

    5.7

  4. D.

    5.5

Attempted by 155 students.

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Correct answer: B

Solution: Compute the total time for the non-pipelined system and for the pipelined system, then take their ratio.

  • Non-pipelined total time = number of tasks × time per task = 500 × 50 ns = 25,000 ns.

  • Pipelined total time for N tasks with k stages and clock cycle C is (k + N − 1) × C. Here k = 6, N = 500, C = 10 ns, so pipelined time = (6 + 500 − 1) × 10 ns = 505 × 10 ns = 5,050 ns.

  • Speedup = (non-pipelined time) / (pipelined time) = 25,000 / 5,050 ≈ 4.9505 ≈ 4.95.

Therefore the approximate speedup for 500 tasks is 4.95. Note that the maximum ideal speedup equals the number of stages (6), but for a finite number of tasks the startup and drain overhead reduce the actual speedup.

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