Question

Which of the following statements with respect to K-segment pipelining are true ?

(A) Maximum speedup that a pipeline can provide is k theoretically.

(B) It is impossible to achieve maximum speedup k in k-segment pipeline

(C) All segments in pipeline take same time in computation.

Choose the correct answer from the options given below:

1. (A) and (B) only
2. (B) and (C) only
3. (A) and (C) only
4. (A). (B) and (C)

Answer 1

Correct Answer - Option 1 : (A) and (B) only

The correct answer is option 1.

Pipelining: Overlapping execution- parallelism improves performance. The aim of using pipelining is to use a single clock per instruction (CPI) which automatically improves performance.
Statement A is true:

\(S = {{tn} \over tp}\) if we assume that the time it takes to process a task is the same in the pipeline and pipelined circuits, we will have tn = kt_p. Including this assumption, the speedup reduces to \(S = {{​​ktp} \over tp}\)=k
This shows that the theoretical maximum speedup that a pipeline can provide is k, where k is the number of segments in the pipeline.
Statement B True:
K × efficiency =speedup
The speedup can not be equals to K till efficiency becomes 1 and in real-time environment efficiency can not become 1 of many reasons like the delay at intermediate buffers, different times taken by different segments to perform their sub-operations which cause all other segments to waste time while waiting for the next clock.
Statement C False: Because different segments can take different times to complete their sub-operations.
Hence the correct answer is (A) and (B) only.