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A 7-stage pipeline separated by a clock 6 ns along with a latch delay of 1 ns. If the non-pipeline clock is also having the same duration and the pipeline efficiency is 50%, then calculate the speed-up factor.

(a) 1
(b) 1.5
(c) 2
(d) 3

1 Answer

5 votes

Final answer:

The speed-up factor is approximately 4.08 when considering the time a non-pipelined processor takes compared to a pipelined processor given the clock and latch delays, assuming an ideal situation with a 50% pipeline efficiency. However, this value is not among the provided choices, indicating potential misunderstandings in the question's context or required information.

Step-by-step explanation:

The question concerns the speed-up factor for a 7-stage pipeline architecture in a computer with a clock of 6 ns and a latch delay of 1 ns, assuming pipeline efficiency is 50%. The speed-up factor is the ratio of the time taken by a non-pipelined processor to the time taken by a pipelined processor to execute the same tasks.

The non-pipelined processor would take 7 stages × (6 ns + 1 ns) = 49 ns to complete one instruction. However, with pipelining, after an initial latency to fill the pipeline, one instruction can be completed every 6 ns (assuming the latch delay can be overlapped with the clock). Thus, for a large number of instructions, the pipeline takes 7 × 6 ns for the initial fill and then 6 ns for each subsequent instruction.

Given a pipeline efficiency of 50%, the effective cycle time is doubled, and the pipelined processor takes 12 ns per instruction after the initial fill. We can calculate the speed-up factor as Non-pipelined time per instruction / Pipelined time per instruction: 49 ns / 12 ns, which yields approximately 4.08. However, such an option isn't provided in the choices, which suggests there may be a misunderstanding. In practice, a 50% pipeline efficiency may lead to longer execution times due to required stalls or other inefficiencies that are not fully captured in this basic calculation.

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