Ezra builds a 1 GHz processor where two important programs A

Ezra builds a 1 GHz processor where two important programs, A and B, take one second each to execute. Each program has a CPI of 1. Susan is tasked with designing the company\'s next-generation processor. She comes up with an idea that improves the CPI of A to 0.9 and the CPI of B to 0.7. But the idea is so complex that the processor can only be implemented with a cycle time of 1.2 ns. Does Susan\'s new processor out-perform Ezra\'s processor on program A? How about on program B?

Solution

Given , 1 GHz processor => clock cycle time = 1/Frequency = 1/(10⁹) = 1 ns

CPI = 1

Therefore, for executing 1 instruction it takes = clock cycle time * CPI = 1 ns * 1 = 1ns

Now,new model is designed so let\'s check for each case

a) FOR PROGRAM A

Clock cycle time = 1.2 ns

CPI = 0.9

Therefore, for executing 1 instruction time taken = 1.2 * 0.9 = 1.08 ns ( more than Ezra\'s processor )

So, Susan\'s processor doesn\'t outrun Ezra\'s processor for program A

b) FOR PROGRAM B

Clock cycle time = 1.2 ns

CPI = 0.7

Therefore, for executing 1 instruction time taken = 1.2 * 0.7 = 0.84 ns ( less than Ezra\'s processor )

So,here in program B Susan\'s processor outruns Ezra\'s processor.