Consider the following processors (ns stands for nanoseconds). Assume that the pipeline registers have zero latency.
P1: Four-stage pipeline with stage
latencies 1 ns, 2 ns, 2 ns, 1 ns.
P2: Four-stage pipeline with stage
latencies 1 ns, 1.5 ns, 1.5 ns, 1.5 ns.
P3: Five-stage pipeline with stage
latencies 0.5 ns, 1 ns, 1 ns, 0.6 ns, 1 ns.
P4: Five-stage pipeline with stage
latencies 0.5 ns, 0.5 ns, 1 ns, 1 ns, 1.1 ns. Which processor has the highest peak clock frequency?
(A) P1
(B) P2
(C) P3
(D) P4
Answer: (C)
Explanation:
Peak clock frequency = 1 / Maximum latency Maximum of latencies is minimum in P3 i.e. P1 : f= 1/2 = 0.5 GHz P2: f=1/1.5 = 0.67 GHz P4: f=1/1.1 GHz P3 : f=1/1 GHz =1 Thus P3 is be the right answer
This explanation has been contributed by Abhishek Kumar.