Answer to Question #313352 in Computer Networks for Anna

Question

Suppose we introduce pipelining on this machine. Assume that when

introducing pipelining, the clock skew adds 5ns of overhead to each

execution stage.

i. What is the instruction latency on the pipelined machine?

ii. How much time does it take to execute 100 instructions?

Answer 1

In the pipelined implementation, the length of the pipe stages must all be the same, i.e., the speed of the slowest stage plus overhead. With 5ns overhead it comes to:

i)The length of pipelined stage = MAX (lengths of unpipelined stages) + overhead = 60 + 5 = 65 ns

ii)Instruction latency = 65 ns Time to execute 100 instructions = 65*6*1 + 65*1*99 = 390 + 6435 = 6825 ns