GATE CSE 2002 | Question: 2.6, ISRO2008-19
in CO and Architecture edited by
25 votes

The performance of a pipelined processor suffers if:

  1. the pipeline stages have different delays
  2. consecutive instructions are dependent on each other
  3. the pipeline stages share hardware resources
  4. All of the above
in CO and Architecture edited by

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3 Answers

35 votes
Best answer

Answer is D.

A: Yes. Total delay = Max (All delays) + Register Delay.

B: Yes, if data forwarding is not there.

C: Yes, like ID and EX shares ID/EX register.

edited by


can same register access cause structural hazard??
for c option it could be register (same) with renaming ..? structural hazard ?
i think yes

structural hazard due to resource conflict, a resource can be register or memory
Well, the register file has SEPARATE input and output ports (Hamacher 6th edition, chapter 5), so how register file can cause resource confilct ?

@Harsh Kumar What if you're writing and reading from the same register?

18 votes
Option D)All Of The Above.

Pipeline suffer from options:-

A) Yes, As pipeline need to work in SYNC all stage should operate in same time. If there are stages taking different time, if there is a slower stage, all faster stage will be bottlenecked by the cycles the slowest stage takes.

B)Yes, As there could be DATA HAZARDS.
           eg: SUB R2,R4,R5
                 ADD R6,R2,R4 //here register r2 result will be dependent on first instruction.

C)Yes, IF(Instruction Fetch) and MEM(Main Memory) stage can cause STRUCTURAL HAZARDS and there may be a chance that both stages need Memory simultaneously, that's why many Arch. slipt the cache as INST cache and Data Cache.
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1. Pipelining is one way of improving the overall processing performance of a processor.
2. This architectural approach allows the simultaneous execution of several instructions.
3. Pipelining is transparent to the programmer; it exploits parallelism at the instruction level by overlapping the execution process of instructions.
4. It is analogous to an assembly line where workers perform a specific task and pass the partially completed product to the next worker.

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