A 4-stage pipeline has the stage delays as 150, 120, 160 and 140 nanoseconds respectively. Registers that are used between the stages have a delay of 5 nanoseconds each. Assuming constant clocking rate, the total time taken to process 1000 data items on this pipeline will be
(A) 120.4 microseconds
(B) 160.5 microseconds
(C) 165.5 microseconds
(D) 590.0 microseconds


Answer: (C)

Explanation:

Delay between each stage is 5 ns.
Total delay in pipline = 150 + 120 + 160 + 140 = 570
Total delay for one data item = 570 + 5*3 (Note that there are 3 intermediate registers)
                              = 585 
For 1000 data items, first data will take 585 ns to complete and rest 
999 data will take max of all the stages that is 160 ns + 5 ns register delay

Total Delay = 585 + 999*165 ns which is approximately 165.5 microsecond. 

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