Hitting The Wall: Thermal Dissipation Prevents Higher Clock Speeds

Hand in hand with increasing performance has come increasing power requirements between 1993 and today. With a maximum TDP of 130 W now, Intel is a lot more power hungry than its competitor AMD. Up until 1999, both companies followed the same technological path, but after that, their paths diverged. Today, AMD clearly leads Intel both where performance and energy efficiency is concerned.

The astute observer will notice that the clock speed race between the rivalling companies has practically come to a standstill. AMD and Intel now try to disguise this fact by using a cryptic product naming system that hides a processor's actual clock speed. In an overclocking test performed two years ago, our lab in Munich already succeeded in pushing a Pentium 4 to 4 GHz with conventional air-cooling methods. In a world-record attempt (our 5 GHz project), we even achieved 5.25 GHz! Yet regular users are still not seeing these speeds today.

The biggest problem that the chipmakers face now is that heat dissipation increases with rising frequencies. So far, neither company has been able to find a satisfactory solution. Instead, they have taken advantage of the advances in miniaturization of the processors themselves, and begun incorporating two processor cores on one die. This technique helps spread the heat more evenly across the processors' surface, while also ensuring higher performance than their single-core counterparts even at lower clock speeds.

For now, however, the 4 GHz barrier seems to remain an insurmountable obstacle - at least while trying to retain justifiable heat dissipation levels. After all, a thermal dissipation loss of 130 watts requires an expensive and extravagant cooling system that isn't easily realized in the mass market. As a result, the Pentium 4 670 remains the processor with the highest frequency on the Intel side. The problem is not as pronounced (yet?) with AMD CPUs, since their clock speeds - and consequently thermal dissipation loss - are quite a bit lower.

Again, we'd like to present a prime example illustrating this development over the past 12 years. While the original Pentium 60 produced in 1993 only sported a tiny passive cooler, today's models require active solutions the size of an infant's head, and often sound more like vacuum cleaners than computer components. If this trend continues, will we eventually see coolers the size of car radiators?

A picture worth more than a thousand words. In the front is a Pentium Overdrive from 1993, complete with its cooler. The looming presence behind it is "only" the standard Pentium 4 cooler from 2005. Will the future bring us even larger coolers?