Suppose we could improve the speed of the CPU in a computer by a factor of 5 (without affecting I/O performance) for 5 times the cost. Also assume that the CPU is used 50% of the time, and the rest of the time the CPU is waiting for I/O. If the CPU is one-third of the total cost of the computer, is increasing the CPU speed by a factor of 5 a good investment from a cost/performance viewpoint?

Bad Investment

Explanation:

Fraction enhanced = 50% = 0.5 (50% CPU is used all times and rest is waiting for I/O.Speed up = 5 (By a factor of CPU speed is increased)Speed up (overall) = Speed up (overall) = CPU = 1/3rd the total cost which means rest of the 2/3rd cost remains the same.New cost of machines = (2/3 * 1) + (1/3 * 5) = 2.33This means new machine is 2.33 times the cost of the old machine.As seen above cost increase is greater then performance increase therefore this is a BAD Investment.

They will be angry and maybe sack you