Before
1990s, the power density was below 10 W/cm2, but when
Pentium® family processor was introduced in 1990 s, the
power density increases exponentially. It is projected that the
processor can be as hot as rocket nozzle when approaching
the end of this decade if the current scaling trend is still
continued without taking any prudence measures to tackle
this power-thermal problem. As a result, Intel® canceled its
4 GHz Pentium®4 in 2001 due to heat dissipation problem.
Consequently, they announced dual core processors.