| <<< Which Parts |
| Getting Started |
| Motherboards |
| CPUs |
| RAM Memory |
| Power Supply |
| Video Card |
| Drive Jumpers |
| Drive Install |
| PCI Expansions |
| Boot Up |
| Peripherals |
| Choosing and Installing Software >>> |
| Optimizing and Overclocking your PC >>> |
The CPU (Central Processing Unit)
If the motherboard is the spine of the computer, then the cpu is the brain. As the name implies, the cpu is where all the computations take place. Therefore it is important to consider relative speed (how many computations the processor can make simultaneously).
As installation of the different makes of CPU can differ between brands, it is generally safer to refer to the manufacturer's instructions that are provided with the CPU. If you are going to use a thermal paste with your CPU follow the directions that came with it for specific details on how to apply it.
The two things that go wrong the most often and most expensively (minimum of a killed CPU, sometimes more -- think cascade!) in building one's own computer are both related to the CPU and the CPU cooler:
- Switching the computer on "just to see if it works" before adding any CPU cooling unit. Without cooling, CPUs heat up at extreme rates (a CPU heats up anywhere between ten times and a thousand times as fast as a cooking area on your stove!) By the time you will get the first display on the screen, your CPU will already be severely overheating and might be damaged beyond repair.
- Mounting the CPU cooler improperly. Read the instructions that came with your CPU and cooler very carefully and ensure you are using all components in the correct order and correct place.
Make sure you get a cooler that is compatible with the CPU you have. Most brands come with multiple mounting brackets that will suit all different chipsets, but it's best to check for compatibility just in case.
If using thermal paste, apply it only to the CPU die (the square piece of silicon in the middle of the CPU) and do so sparingly -- most modern CPUs take no more than a grain of rice sized dab of thermal paste. Some people do like to wipe some onto the heatsink's surface and then wipe it smoothly off so that bits of it may get into tiny holes for better heat transfer. See Arctic Silver Instructions for more info on how to apply and remove thermal paste / grease. (It was written to be specifically for Arctic Silver paste, but the same techniques can be applied to other brands of thermal paste.)
If using a thermal pad supplied with your cooler, make sure you remove any protective tape just before installing and do not get it dirty - and do not combine thermal pads with thermal paste, it's either one or the other - NEVER BOTH. Then, check that you install the cooler in the right orientation and that you set it flat on the CPU die without exerting undue pressure on any edges or corners - the latter can make small pieces of the die break off, killing the CPU.
One option you may consider, before installing the heatsink, is to "lap" the heatsink, which means to smooth out the bottom surface. To do this, start by sanding in smooth circular motions with a coarse grain sandpaper to smooth out the worst of the uneveness, then, as it starts to get smoother, switch to a finer grained sandpaper (the numbers go up as the sandpaper is finer, so something such as 60 is coarse while 220 will be very fine.) If you get it right, it should have a surface which feels completely smooth to the touch where you can almost see a reflection in it. Some companies producing heatsinks lap the surface themselves and this will be unnecessary, but, it is very rare. A lapped heatsink is far more effective due to having better contact with the chip.
Tighten the cooler using only the specified holding devices - if you did everything right, they will fit. If they don't fit, check your setup - most likely something is wrong. After mounting the cooler, connect any power cables for the fan that is attached onto the cooler. Then, if everything is seated tightly and firmly, you can safely run your first test, making sure the CPU fan does run (you have a few seconds of safety margin here, but if the fan is not running, switch off the system quickly, and then check your cabling.)
As an aside to the instructions above, it has been my personal experience that fitting the CPU and heat sink is best done on a supportive surface (a telephone directory on a table in my case) prior to installation, to avoid excessive flexing of the motherboard.
