Answer to Question #313963 in Computer Networks for Anna

Question

Suppose we introduce pipelining on this machine. Assume that when

introducing pipelining, the clock skew adds 7ns of overhead to the execution

stages.

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

ii. How much time does it take to execute 200 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 7ns overhead it comes to:

i)The length of pipelined stage = MAX (lengths of unpipelined stages) + overhead

$= 60 + 7$

$= 67 ns$

ii)Instruction latency = 67 ns Time to execute 200 instructions

$= 67\times6\times1 + 67\times1\times199$

$= 402 + 13333$

$= 13,735 ns$