In recent years, we have seen an abrupt halt in the traditional increase in CPU frequency, where new processors have the same frequency but an increasing number of cores. The reason for this abrupt change is that we have reached the limit to the power density chips can withstand using current cooling techniques. As a synthetic example, doubling the frequency of the 3.2 GHz Intel Core i7 would roughly yield a thermal design power (TDP) of a kilowatt! The reason is simple: the power consumption is directly proportional to the cube of the frequency . Both Intel and AMD now use this proportionality to their advantage by designing multi-core CPUs: two cores running at 85% of the frequency can oer 170% of the performance of a single core, yet both solutions consume roughly the same amount of power.