Q15.Marks: +2.0UGC NET Paper 2: Computer Science 2020
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✓ Correct
2.(B) and (C) only
3.(A) and (C) only
4.(A). (B) and (C)
Solution
The correct answer is option 1.
Key Points
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 = ktp. 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 CFalse: Because different segments can take different times to complete their sub-operations. Hence the correct answer is(A) and (B) only.
