Build The Ultimate Custom PC (2005)

Chapter 14 — Fitting the Basic Parts 239

FIGURE 14-21: Heatsink and cooler fan assembly.

Applying Thermal Grease

Many of the heatsink assemblies supplied with CPUs already have a small patch of thermal grease stuck onto the bottom on the heatsink (see Figure 14-22). This means that you don’t have to worry. All you have to do is fit the heatsink over the CPU, and you are ready to go. There’s no need to mess about with any additional thermal grease.

Never add additional thermal grease on the top of any thermal grease already stuck to the heatsink. If you want to use different grease, you will have to remove the existing grease first by carefully scraping it off with the plastic spreader.

Don’t be too harsh. You don’t want to damage the smooth surface of the heatsink.

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FIGURE 14-22: Ready-applied thermal grease.

Another vital component in the CPU cooling system is the thermal grease that creates a conduit for the heat to pass from the CPU to the heatsink. Air is a very good thermal insulator, and if you were to fit a heatsink onto a CPU without thermal grease, the thin layer of air trapped between the two would act as an insulator and trap heat at the CPU, causing a dangerous temperature build-up that would damage the CPU. Thermal grease eliminates this and provides an excellent medium for heat to move from the CPU to the heatsink.

Thermal grease comes supplied in little tubes (see Figure 14-23). All you need to do is apply a little grease to the base of the heatsink and spread this into the thin layer using a piece of cardboard. Generally, a plastic spreader is supplied to do this job. You only want a thin layer (paper thin, no more), but it does need to be free from air bubbles, which can cause pockets of heat to build up.

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FIGURE 14-23: Thermal grease.

One question many people ask is how much of an area of the bottom of the heatsink they need to cover with thermal grease. You certainly don’t want to go covering the whole thing — this is both wasteful and messy. You only need to apply thermal grease to the areas of the heatsink that are going to be in contact with the CPU.

Along with the plastic spreader, many thermal grease tubes will come with paper templates for a variety of CPUs that help you get the grease on in the right spot. You apply the template to the base of the cooler, add the thermal grease, and spread it. This way, not only do you get it in precisely the right spot, but you also get a paper thin layer onto the cooler, which is precisely what you are looking for.

Never smear thermal grease on with your fingertips or touch the grease with your fingers. Not only is it nasty stuff, but no matter how clean your hands are it will be contaminated with oils. Also, you’ll get far too much on the cooler! If you happen to touch the grease accidentally, wipe it off with a clean cloth and start again.

Fitting the CPU Cooler/Fan Assembly

The CPU heatsink and cooler assembly fit over the top of the CPU and clip either to the surround of the ZIF socket or to a plastic frame fitted to the motherboard (see Figure 14-24).

Different coolers fit onto the board in different ways, and the best way to guarantee that you get this step right is to read the instructions. What follows is general guidance on fitting the cooler to the CPU. For specifics, consult the documentation that accompanied your cooler.

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FIGURE 14-24: Heatsink clips.

Spring-Loaded Cooler Assemblies

Coolers are generally fitted over the CPU by means of a spring-loaded assembly that holds the cooler tight over the CPU (see Figure 14-25). This tight fit is essential in order to create a proper fit that will allow the heat to pass from the CPU to the heatsink so that it can be safely dissipated.

Use the following steps to fit your cooler over the CPU:

1.The trick with these coolers is that you have to fit one side first (generally the side without a thumb catch on it), as shown in Figure 14-26. To do this, you might have to angle the heatsink in such a way that it allows you better access to the clips.

2.And of course, you have to fit the next side (see Figure 14-27). The heatsink that we have for our AMD processor needs to be pressed into place with a straight-edged screwdriver. You fit this into the slot on the plastic thumb catch and press downward and outward slowly but carefully.

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FIGURE 14-25: Spring-loaded catches.

FIGURE 14-26: Fitting the catches on one side.

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FIGURE 14-27: Fitting the second catch using a straight-edged screwdriver.

3.Press gently and smoothly but firmly and the catches will come together and fit.

4.Sometimes there’s a locking mechanism to tighten up the spring and keep it in place, while other times there isn’t. This depends on the cooler assembly you have. If necessary, tighten your locking mechanism.

Be careful when fitting the heatsink. Sometimes, quite a bit of pressure is needed to get the spring clips into place, and you need to take special care not to damage the motherboard or knock off any components.

Connecting the Fan to the Motherboard

Finally, that fan on the cooler needs power. The fan draws its power and supplies information on how fast it turns via a thin 3-wire cable (4-pin for LGA 775 CPU coolers) that connects to

Chapter 14 — Fitting the Basic Parts 245

the motherboard via a 3-pin connector head. Spotting this on the motherboard can be tricky, but there are only normally two connectors like it — the CPU fan connector and a case fan connector.

To tell the difference, you need to look closely at the writing on the motherboard to spot the right connector. (See Figure 14-28.) Fit the CPU cooler fan to the header marked “CPU Fan” or something similar, or take a look through the instructions that accompany your board.

FIGURE 14-28: Markings on the board for the CPU fan header.

Generally, your instructions will have diagrams of the board showing all the connectors. This makes the right header much easier to find and is much better than squinting at microscopic text!

The connector and header are both keyed, so there’s no chance of fitting them the wrong way. See Figure 14-29.

With that done, the fitting of the CPU and cooler is done and it’s time to move on to the next item on the list — wiring the board.

You might want to take a small break at this point, get a cup of coffee, and find that flashlight we mentioned earlier!

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FIGURE 14-29: CPU cooler fan header and connector.

Wiring the Motherboard

Your motherboard should now be sitting in the midst of a lot of wiring. There are two sources of these wires:

Case wiring

PSU wiring

A flashlight is definitely going to come in handy for this stage of the build!

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Case Wiring

Wiring up the case to the motherboard can be tricky, not because it’s in any way difficult but because it can be tricky to match the right connector to the right header on the motherboard.

The positions of all the headers, along with the connectors from the case, all vary, so the information here should be considered generic. The best way to find out what goes where is to consult the manual that came with your motherboard. This will show you where all the connector headers are.

Most of the connector headers and connectors themselves aren’t keyed, and there is a chance of fitting them incorrectly. Despite this, there is little or no risk of damage. If you connect something the wrong way (say, a hard disk drive LED light or the power LED), then the LED simply won’t work. After the testing phase, all you have to do is reverse the connector, and it will then work!

Connectors that may need fitting include:

Power switch

Power LED

HDD LED

Reset button

Case speaker

Case fan

USB/FireWire connectors

Audio connectors

Figures 14-30 and 14-31 show the case wiring before and after being fitted.

PSU Wiring

With the case wiring out of the way, you’re now ready to connect the PSU to the motherboard. This is a simple job because you have only two connectors:

The 20-pin (or 24-pin) motherboard power connector.

The 4-pin auxiliary power connector, which supplies extra power to the motherboard to cater for modern AMD and Intel CPUs.

Both of these connectors are keyed, and there’s no risk of plugging a connector into the wrong socket.

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FIGURE 14-30: Case wiring.

FIGURE 14-31: Case wiring fitted.