minority (10%) of functions used spend majority of their time (60%) waiting for RAM. So in the end it is 60% from 10% which is only 6%. Give or take. The problem is more complex, but basically modern CPUs are not limited by the processing power, because it is extremely easy to just add extra adder or multiplicator to the CPU. What is limiting is waiting for data from RAM/caches, because memory just cannot keep up with 4GHz+ CPUs.