Step 3 – Do I need a 3-pin fan or a 4-pin (PWM) fan?
Most if not all motherboard these days have a 4-pin CPU fan header on the motherboard. This is so you can set the temperature/speed ratio of the CPU cooler in the BIOS or through supplied utility software that comes with most motherboards. For instance if the your maximum CPU temperature is 70 °C, you could say in the BIOS that the CPU fan can run on its lowest speed until it hits 65 °C and then turn up the speed to say medium or high when it gets too hot. With his method, you do tend to notice the fan revving up and down so you do need to play about a bit with those temperature/speed ratio’s until you get the balance right. Also, the amount of control you have over the fan speed may range from not much to quite a lot. Generally the more expensive the motherboard, the more control you have. On a good board, you can have the fan speed typically anywhere between 40% and 100% of full speed. On a cheaper board you may only get the option of slow, medium or fast! Many people still prefer 3-
