While Moore's Law will probably continue to hold for some years to come, another problem is starting to overshadow it: heat dissipation. Smaller transistors make it possible to run at higher clock frequencies, which requires higher using a higher voltage. Power consumed and heat dissipated is proportional to the square of the voltage, so going faster means having more heat to get rid of. At 3.6 GHz, the Pentium 4 consumes 115 watts of power. That means it gets about as hot as a 100-watt light bulb. Speeding up the clock makes the problem worse.

In November 2004, Intel canceled the 4-GHz Pentium 4 due to problems dissipating the heat. Large fans can help but the noise they make is not popular with users and water cooling, while used on large mainframes, is not an option for desktop machines (and even less so for notebook computers). As a consequence, the once-relentless march of the clock may be temporarily stymied, at least until Intel's engineers figure out how to get rid of all the heat generated in an efficient way. Instead, Intel's future plans call for putting two CPU's on a single chip, along with large to voltage and clock speed, two CPUs on a chip consumes far consequence, the gain offered by Moore's Law may be increasingly exploited in the future to include larger and larger on-chip caches, rather than higher and higher clock speeds (because memory does not consume much power).

(A.S.Tanenbaum, Structured Computer Organization, 5th Ed., 2006, p.41–42)

Segundo o texto, o processador Pentium 4 de 4GHz