Fan speed control how-to, 2-pin vs.3-pin vs. 4-pin [Solved] - fans - Components
2-pin and 3-pin fans can only be speed controlled by varying the voltage to the fan. 4-pin PWM fans are speed controlled by a special PWM control wire (the 4th pin) that tells circuitry in the fan how fast to turn. 2 and 3 pin takes a fan controller to ch...