![]() So, the power delivery graph for a PWM fan looks something like this (called a square wave or pulse wave) – ![]() However, the voltage (12V) applied to a PWM fan won’t change regardless of fan speed when in this mode. Steady pulses of power are used to vary fan speeds in PWM mode, which means that the fan motor switches from the ON to OFF state and back to ON rapidly. This type of fan requires a 4-pin fan connector like the one shown below:Īs you can see in the PWM fan pin diagram above, the 4 th pin (blue) allows the motherboard to send a PWM signal to the fan, which controls its speed. Simply put, a PWM fan turns off and on very fast to run at lower speeds. PWM ( Pulse Width Modulation) fans allow motherboards to control fan speeds using rapid power pulses (on-off cycles). If you want to find out more about these mysterious terms, read on! What is PWM and How Does it Work? ![]() If your motherboard fan header only has 3 pins, pick DC regardless of whether you have a 4-pin PWM or 3-pin DC fan. On the other hand, if you have a 4-pin fan connector, select PWM mode. If you have a 3-pin fan connector, pick DC mode. Auto Fan Modes The Short Answer – DC or PWM Mode?īefore getting started on the explanation, I’ll condense it down for those who want a quick answer. ![]() DC mode fans and what modes to use for effective cooling and low noise levels. If you’ve ever gone rummaging through your BIOS, you might have stumbled across the terms PWM, DC, and Auto in the fan control section.
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