Take a look inside your computer, what do you see in there? If you're like most people you will see a tangled bunch of power and IDE cables blocking airflow from your front mounted case fan to your AGP slot and your processor. Usually the case fan covers the ISA and PCI slots. Major computer manufacturers hire special engineers just to make sure that air flows through your case to all your peripherals and components unrestricted but most of use homemakers are faced with limited success from standard case fans and processor fans because we don't want or know how to make space in the case for airflow. If you see the diagram below:
This is the picture of the standard case albeit a little ugly. Please note that this is a case without any additional cooling aside from the case fan and the processor fan. The clutter of wires and the AGP card add to the blockage of airflow coming from the case fan up to the higher regions of the case so there is a definite temperature increase from the bottom of the case toward the top. This means that because cool air cannot easily get past the bundle of wires and cards, the cool air will probably not be effective in cooling the processor of the computer. Now if you take a look at the top of the case. Since there is not much cool air from the case fan is reaching the top, it's pretty warm up there. That is thanks to the power supply, which usually generates a good amount of heat, the 5.25" drives which usually spin fast to cause more heat and of course the hard drive. The newer 7200RPM and 10,000RPM drives are notorious for giving off high amounts of heat. Now you have a lot of components that do nothing but give off heat and that heat is blocked from going anyplace because of the restriction of airflow. So the heat remains on the top areas of the case until it is pushed out through the back. Now you have hot areas in the case and the processor comes into play. Processors give off a LOT of heat. But they usually have fans attached to heatsinks. What good are these fans when all they're blowing into the processor is hot air. The airflow I just explained to you is why some computers fail.
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