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An instruction pipeline has stages as given in diagram

A program consistsing of 9 instruction I1,I2....I9 is executed in this pipeline processor.instruction I3 is the only conditional branch instruction and its branch target is I7,If the branch taken after EI state,the time needed to complete the program is?

in CO and Architecture by Boss (11.2k points)
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The maximum delay is taken by the stage FO which is 11ns.

The Buffer Delay is 1ns.

Hence, each stage takes maximum 11+1 = 12ns

I1 FI DI FO EI WO                
I2   FI DI FO EI WO              
I3     FI DI FO EI WO            
I7             FI DI FO EI WO    
I8               FI DI FO EI WO  
I9                 FI DI FO EI WO

Hence, Total stages = 13

Therefore, total time = 13*12 = 156ns

by Active (1.3k points)
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but, It is not said that , pipleline is synchronous.  ??

time to complete I1 = 39 ns or 60 ??  

I think I1=60ns only because I tried this type of question from GATE and also on Made Easy site and everywhere they have done it like this, even though they haven't explicitly mentioned that the pipeline is synchronous.
@Vijay. This is just a point in the execution of large no. of instructions.

So, it will definitely be 60.
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