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Monster-Mod: Passive Convection CPU Water-Cooling (Part 2 of 4)

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The budget for the water-cooled PC is tight and so is the deadline. Cyrus Peikari scrambles to find the pieces he needs to complete this Monster-Mod.
Editor's Note: This is Part 2 of a 4-Part series. Be sure to read Part 1, Part 3, and Part 4.
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With time running out before our publication deadline, the pressure was on to build a monstrous CPU water-cooler. But we also had a tight budget for the project. And with commercial water-cooling kits running into the hundreds of dollars, we would have to improvise a homemade kit.

What Is a Water Block?

The most expensive part of the water-cooled system is the water block. A water block is distantly analogous to the lungs of your human cooling system. This is where the heat is transferred away from the CPU. A good water block will have a copper base, rather than aluminum, in order to transfer heat much faster.

The copper base of a water block is tightly clamped against the CPU; thermal paste is sandwiched in between to ensure a good contact. Above the copper base are fittings where the water flows in and out. A typical water block has one inlet and one outlet. Cool water is pumped in, warmed, and washed out. To improve the exchange of heat, some water blocks have "mazes" or patterns cut into the copper like deep grooves. This creates local turbulence and increased surface area of the copper-water interface. Figure 1 shows a typical water block.

Figure 1Figure 1 A typical water block. This model from Asetek has clear Lucite on top of the copper, which allows you to see the water flowing through the maze.

A good water block will cost about $50 new; used will be slightly cheaper. I suggest buying a new one from a reputable company. The water block is where your water interfaces with the powered CPU and motherboard. Any leak here is going to be a total disaster, and could cost you a couple of thousand dollars in damage on a high-end system.

You can find the part on eBay; just do a search by vendor name. Reputable water block vendors include Danger Den, Koolance, Asetek, and PolarFlo. A key consideration when buying is to get a block that supports your CPU type. In our case, we need a block that supports Socket 478 (for our Pentium 4 CPU). We are also looking for half-inch fittings; smaller diameter will limit water flux.

In addition, ease of installation is important. We opted for the very basic Asetek water block shown in Figure 1. While this brand can be pricey, we found this unit for $50 on eBay. It's not my favorite hose connector configuration, but it's easy to install on our motherboard, as we'll see later.

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