If two processors given below run exactly the same program i

If two processors given below run exactly the same program in a perfect scenario, which processor runs faster and how many times faster?

Assume that the number of instructions being execute is very large, e.g. millions of instructions. Also, assume the pipeline execution of processor B is perfect, i.e. no branch mis-prediction penalty and no cache miss penalty (the two processors do not use cache).

Processor

Clock Frequency

Non-pipeline Processor A

10MHz

Three-stage Pipeline Processor B

28MHz

Solution

Time taken by processor A to execute 1 instruction = (1/10)*10^-6 = 0.1*10^-6 sec

Let stage delay in processor B for each stage is 1*10^-9 sec.

Now, time taken by processor B to execute 1 instruction = (1/28)*10^-6 + 2*10^-9

= 0.03571*10^-6 + 2*10^-9 = 0.03571*10^-6 + 0.002*10^-6 = 0.03771*10^-6 sec

As, we can see processor B takes less time to execute 1 instruction. Therefore, processor B runs faster than A.

b.) Now, processor B will be (0.1*10^-6)/(0.03771*10^-6) = 2.65 times

Hope it helps.