Question

One usual fallacy is to consider the computer with the largest clock rate as having the largest performance. check if this is true for p1 and p2.

Answer 1

Processor   Clock Rate   CPI  Instructions
P1                4 GHz         0.9        5.0E9
P2                3 GHz         0.75       1.0E9
According to these values; when we calculate TP1 and TP2;
TP1= 0.9 x 5 x 109/ 4 x 109= 1.125 seconds
TP2= 0.75 x 109/ 3 x 109= 0.25 seconds
Thus, in this case P2 has better performance because of its lower CPI and number of instructions.

Answer 2

A computer with the largest clock rate does not mean it will have the largest performance. By overclocking you may be able to reach the maximum capacity of a CPU, but perhaps buying an upgraded CPU with more processing power will out do the former computer minus the overclocking method to the latter upgraded PC.