Intel's Penryn family of 45 nm processors is making waves, but still hasn't had much desktop market penetration, because the firm has so far only released the expensive "Extreme" QX9650 model. Compare Prices on Core 2 Extreme QX9650 As enthusiasts look forward to upcoming lower-cost versions that will give them the best "bang for the buck", a few extreme overclockers have already pushed these beyond 6 GHz using equally extreme below-ambient coolers.

As indicated in our Penryn premiere, major improvements over earlier Core 2 models include a die shrink for higher yields, and a new dielectric for reduced leakage current. The combination of these production features could eventually translate into lower pricing and lower power consumption with reduced heat. Any time we see a die shrink we expect higher clock speeds will soon follow, and the cool-running Yorkfield four-core version was capable of reaching 4 GHz on air cooling.

Lower heat is a step in the right direction when insane clock speeds are the objective, but Intel's efforts have focused instead on reducing the system's "carbon footprint" and operational cost while increasing longevity of related components. These seem like lofty goals, but we really wanted to how far we could push the performance envelope using common parts that most enthusiasts can afford.

Is More Cooling Really Needed?

While these new processors might run "cool" on nothing more than a heat sink and fan, extreme cooling has always been the "trick" to reaching the highest overclocked speeds. High overclocks require relatively large voltage increases for greater signal strength, which can overwhelm the inherent efficiency of any integrated circuit design. Excess voltage creates heat, heat causes instability, and adding even more voltage to overcome that instability only further increases heat until the component reaches its breaking point. The only way to break this never-ending loop of voltage and heat is to increase cooling capacity.

Extreme overclockers have used wild cooling methods - including dry ice and even liquid nitrogen - but none of these is practical for daily use. The next step towards "daily use" practicality has come from cascade-type phase change (refrigeration) units, where the primary cooler is itself cooled by a second cooler, but these are expensive, complicated, and require skills beyond those of most builders.

Thus, the majority of enthusiasts won't use anything more elaborate than a large water cooler. We've gotten such good results from Swiftech's Apogee GT water block, MCP-655b pump, and three 120mm radiators, that the kit is now mounted into one of our test benches.

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