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Consider an instruction pipeline with 5 stages taking 7 ns, 4 ns, 3 ns, 8 ns, and 5 ns respectively. The delay of an inter-stage register is 2 ns. What is the approximate speedup of the pipeline in the steady state under ideal conditions compared to the corresponding non-pipelined implementation?

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Final answer:

The speedup of the pipeline is calculated by comparing the total non-pipelined time per instruction (35 ns) to the pipelined cycle time (10 ns). Under ideal conditions, the pipeline achieves an approximate 3.5 times speedup compared to the non-pipelined implementation.

Step-by-step explanation:

To calculate the speedup of a pipeline, we compare the time it takes to process a sequence of instructions in both pipelined and non-pipelined architectures. In a non-pipelined implementation, each instruction would be processed sequentially, thus taking the sum of all stage times plus the inter-stage register delays.

The total time for a non-pipelined implementation would be:

  • 7 ns for stage 1
  • 4 ns for stage 2
  • 3 ns for stage 3
  • 8 ns for stage 4
  • 5 ns for stage 5
  • Inter-stage register delay: 4 * 2 ns (since we have four inter-stage registers)

Therefore, the total non-pipelined time = 7 + 4 + 3 + 8 + 5 + (4 * 2) = 27 + 8 = 35 ns.

In the pipelined implementation, in steady state, a new instruction can be initiated after the longest stage time. Since stage 4 is the longest stage at 8 ns, and the stage is followed by an inter-stage register of 2 ns, we get a clock cycle of 10 ns for the pipeline.

To determine the speedup, we compare the non-pipelined time per instruction to the pipelined cycle time:

Speedup = Non-pipelined time / Pipelined cycle time = 35 ns / 10 ns = 3.5

Therefore, under ideal conditions, the pipeline would achieve approximately a 3.5 times speedup compared to the non-pipelined implementation.

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