Side note: The 'RPM Speed Signal' pin (rotations per minute) in the picture is telling the motherboard at which speed the fan is spinning, it is not controlling the fan.

With a PWM-controlled fan, the board powers it with a steady 12V, and the fan speed is controlled through the fourth pin via a PWM signal. With a DC-controlled fan, the fan speed is regulated by the board powering it with lower or higher voltages (say, between 3V and 12V) instead of steady 12V. A 4-pin plug means it's PWM (pulse width modulation) controlled. It may say N/A either because nothing is connected to it, or it may say N/A because said header cannot be altered.A three-pin plug means the fan is DC (= direct current) voltage-controlled. That 'Power fan speed' in the bios may be for that connecter. With the PWR_FAN headers, the speeds of the fan connected, cannot be controlled by the motherboard nor can it be altered in the BIOS. These headers were originally for PSUs but pretty much any fan can be connected to one. It's not a no-name brand, dodgy PSU or Rosewill either, so I wouldn't figure it to break after only a couple months.Ĭase (if it matters): Rosewill Galaxy 01-A Some motherboards have a header labled PWR_FAN. I think the fan is working fine and that the speed reader just melted or something, but I want to make sure. The only thing that seems strange is that the boot time is a bit longer than usual, but I assume that's just the HDD having problems, because again, this is probably the hottest it's felt yet, me having built in in the winter. All the temps are still >40 C, where I'd figure them to be in this heat. When the PC boots, it seems slightly quieter in my opinion as well, I don't know if I'm just paranoid about it or what, but I think it's fine, since it's very hot where I am, and the computer isn't instantly catching on fire like I'd figure it would do if the fan broke. it says 'Power fan speed: N/A' in the BIOS.

Bios fan speed