Liquid cooling takes advantage of the key features that a larger radiator offers compared to local sinks, with the added benefit that the radiator can often be mounted in a cooler air stream.
That explains why a large radiator sits at the front of most automobiles, but in the case of overclocking, complexity and inconvenience have limited the number of liquid-cooling applications in PCs. Most liquid cooling systems focus on the CPU, since adding other components to the loop makes servicing a nightmare. In particular, removing a liquid cooling system from graphics cards requires extreme caution and plenty of extra time to drain the system, which must then be refilled and re-purged (to remove air from the water lines) before it can be used again. This could easily turn five minutes of diagnostic work into a one-hour ordeal--and that's if you know what you're doing.
But liquid cooling’s inconveniences can be more easily justified in situations where air cooling simply isn’t adequate. We’ve run into this exact problem when overclocking multi-card graphics configurations, and our December $2,500 3-Way SLI PC was the most noteworthy example. Packing three double-slot cards together limited airflow to the intake fans of the top two cards, so that cooling was barely adequate to keep up with the configuration’s stock speed. Don't even think about overclocking in that situation.
For overclockers, the opportunity to seek significant performance gains makes liquid cooling’s troubles worthwhile, and several companies are ready to fulfill those needs. Options include buying an air-cooled card and adding an expensive liquid-cooling “water block” or purchasing a card with the water block pre-attached, such as the GeForce GTX 285 Infinity Edition from Zotac.
Liquid-cooled graphics cards typically cost around $50 less than the sum of their parts (high-end water block plus a high-spec card), so the smart money for anyone looking to water cool is to buy these parts pre-assembled. Zotac adds one more reason to purchase its product by pre-overclocking its GPU and RAM to extra-high speeds, selling the card with a warranty that home overclockers typically must sacrifice. That also means that each GTX 285 Infinity Edition is hand-selected for its ability to support the rated speeds, while the purchaser of a reference-clocked card must rely on the luck of the draw to reach similar or greater speeds.
Overclockers aren’t the only market for liquid-cooled electronics, as similar methods have been used to address airflow constraints in densely packed servers. And let’s not forget home-theater and audio-studio applications where liquid cooling allows enormous passive radiators to suffice in situations that would have otherwise called for noisy high-speed fans. All of these markets share a common goal of increased cooling capacity at reduced use of local space and these are things that even non-overclocking performance enthusiasts can appreciate.