MadeEasy Test Series: CO & Architecture - Pipelining

Question

i got  2.66  my answer is not match..plz check

Answer 1

We are not given the number of processes ..Hence we consider :

Speedup   =   Time taken to perform one instruction in non pipeline / Stage delay of pipeline

                =   CPI * Cycle time_{non pipeline} /  Cycle time_pipeline

                =   4 * (1 / 3 * 10⁹)  /  (1 / 2 * 10⁹)

                =   8 / 3

                =   2.67

Hence the speedup  =  2.67 

But none of the options are given correct here..So they should be corrected..

Comments

i also get same ....thks

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@Habib I have a question

Speedup = CPI * Cycle time_{non pipeline} /  CPI *Cycle time_pipeline

U took CPI of pipeline=1,rt?

but how do u know it is a single stage pipeline?

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Cpi of an ideal pipeline is 1..

Further single cycle CPU is defined for non pipelined system as  u will have separate stages and hence cycles in pipelined system..

But average cpi of pipelined system is taken as 1 the reason being : when the pipeline becomes full i.e. all stages are occupied by some instruction after they every instruction gets completed consequently in one subsequent cycles each..

I hope I have made my point clear @srestha..

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But if CPI is not 1 , as it is not mentioned in question that it is an ideal pipeline, then?

See, this is the issue in this question too https://gateoverflow.in/8288/gate2015-1-38

Can u answer my query there?