"The Auras LPT-700 is an Intel-only socket 775 heatsink designed for quiet cooling. The LPT-700 is equipped with a 92mm PWM fan that scales in speed from 700-2100RPM with compatible motherboards, and at its fastest speed is moderately audible. Pulse Width Modulation (PWM) compatible fans are noted by their 4-pin power connectors, and what PWM does is enable the BIOS to directly control fan speed. Versatility is the key to any good heatsink, and the PWM approach ensures you computer can keep itself cool when under load, yet decrease fan noise when it isn't."