Processor A has a CPI 12 and a clock rate of 2 GHz Processor

Processor A has a CPI 1.2 and a clock rate of 2 GHz. Processor B has a CPI of 2.2 and a clock rate of 4 GHz. Both Processors implement the same instruction set. Determine the time per instruction for each processor and write it in the correct spot. Which processor is faster? How many times faster is it than the slower processor? Show your work! Processor A time per instruction _____ Processor B time per instruction _____ Which is faster? How many times faster?

Solution

Since both has same instruction set, we have the following formula

Clock Rate/CPI = Total number of instructions executed per second

For Processor A:

CPI=1.2

Clock Rate=2 GHz

Clock Rate/CPI = 2/1.2 = 1.7 * 10^9 Instructions per second (Converted Giga 10^9)

For Processor B:

CPI=2.2

Clock Rate=4GHz

Clock Rate/CPI=4/2.2 = 1.8 * 10^9 instructions per second

Now you can see that processor B is faster than Processor A

Time to execute 1 instruction in Processor A is

1/(1.7 * 10^9) = 1/1.7 * 10^-9 = 0.58 * 10^-9 (10^-9 = 1 nano second)

= 0.58 nano seconds to execute 1 instruction

Time to execute 1 instruction in Processor B is

1/(1.8 * 10^-9) = 0.55 nano seconds to execute 1 instruction