PWM stands for pulse width modulation. PWM fans and/or pumps are found in some CPU coolers and use an integrated circuit to control the speed of a fan or pump and, therefore, how much cooling it’s providing to the CPU. PWM fans and pumps can alter their speed and airflow based on the CPU’s temperature.
To use this feature, you’ll need a motherboard with a PWM header and the appropriate software. Most mainstream motherboards have at least one 4-pin PWM header, and high-end motherboards usually have to four to six. Note, older fans may use 3-pin connectors.
PWM works like a switch, turning on and off while controlling the level of power delivered to the fan or pump. PWM fans works in correlation with the motor, receiving full power or zero power.
Credit: EKWBPWM is also used in servo motors, voltage regulation, telecommunications and audio equipment.
This article is part of the Tom's Hardware Glossary.