Startech 120x25mm computer case fan with pwm ndash pulse width modulation connector the fan12025pwm 120mm pwm case fan adds an efficient air cooling solution to computer cases or other enclosures to help ensure optimal performance from internal components with pulse width modulation pwm technology the fan speed can be dynamically controlled by the motherboard so the fan runs at a speed that suits the operating conditions lowering power consumption and fan noise when the system is idle