Question

Computers A and B implement the same ISA. Computer A has a clock cycle time of 200 ps and an effective CPI of 1.5 for some program and computer B has a clock cycle time of 250 ps and an effective CPI of 1.7 for the same program. Which computer is faster and by how much?

Answer 1

Computer A is 1.41 times faster than the Computer B

Step-by-step explanation:

Assume that number of instruction in the program is 1

Clock time of computer A is
`CT_(A) =200 ps`

Clock time of computer B is
`CT_(B) =250 ps`

Effective CPI of computer A is
`CPI_(A) =1.5`

Effective CPI of computer B is
`CPI_(B) =1.7`

CPU time of A is

`CPU_(time)=instructions * CPA_(A) * CT_(A)\\CPU_(time)=1 * 1.5 * 200=300 sec`

CPU time of B is

`CPU_(time)=instructions * CPA_(B) * CT_(B)\\CPU_(time)=1 * 1.7 * 250=425 sec`

Hence Computer A is Faster by
`(425)/(300) =1.41`

Computer A is 1.41 times faster than the Computer B