MadeEasy Test Series: CO & Architecture - Pipelining

Question

The following sequence of instructions is executed in basic 5 stage pipeline ( F D E M W). Assume data dependency is resolved by Operand Forwarding. Load instruction output present at 4th stage and ALU instruction output is at third stage. Assume each stage takes one cycle.

How many instructions must be inserted to achieve CPI = 1 by using Operand Forwarding ?

A. 3

B. 4

C. 5

D. 6

Comments

Is the approach Correct ?

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Can i use this approach always ?

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above solution is correct. That is the way u approach it.

Not sure how u approached the solution.

Answer 1

key point is :

first execute pipeline without operand forwarding.(15 cycles)

second  execute pipeline with  operand forwarding.(10 cycles)

and then subtract both you will get required ans(5 cycles)