Intel's Pentium 4 burst onto the world stage. It boasted a completely new microarchitecture - Intel's first for five years - called NetBurst. Intel made grand claims for the design, based around Hyper Pipelined Technology.
But NetBurst-based Pentium 4 CPUs were actually slower, clock for clock, than the Pentium IIIs they replaced. The idea was that NetBurst would compensate for this poor performance at low clock speeds by supporting stratospheric frequencies.
Intel claimed an eventual target clock speed of 10GHz was possible as the design matured.
Alas, it wasn't to be. As clock speeds increased, the company was unable to keep on top of power consumption, which rose proportionally. By the time the last Pentium 4 CPUs with 3.8GHz clock speeds came onto the market, they were consuming up to 130W of power.
That created a huge heat problem and led to horribly noisy PCs, with fans running at full speed almost permanently. Intel simply couldn't manage to design a model with a clock speed higher than 3.8GHz - the power consumption was too great.
It was forced to abandon NetBurst, and in 2006 - after a frantic 18-month about-face behind the scenes - it revealed the Core microarchitecture.
This threw away the ideas behind NetBurst, owing its design principles to the low-power Pentium M architecture. The deep pipelines, high clock speeds and huge power consumption of NetBurst were consigned to history.