[Question] Fans with speed control

The motherboard itself controls the fans.  Asus uses it's own Q-fan technology while others call it a different name.  You could try SpeedFan.
http://www.almico.com/speedfan.php

It's a utility that reports fan speeds, temps, voltages, etc. It also can control the fan speeds directly on some motherboards (handy chart is available to check for your motherboard).

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The mobo only does this if the model supports this functionality.
I wouldn't take this for granted in every case; especially cheaper models will either have this implemented improperly or lack it completely.

In any case, your fans will need at least three wires (some models have four) for this to work, otherwise, the current RPM cannot be reported to the mobo.
It may still control the speed, however, then you do not get any readout on the RPMs and hence cannot set a minimum or maximum value which means the mobo could either switch off a fan completely (bad idea in some cases) or make them spin too fast (could become quite noisy).

In my experience, it is best to use the BIOS for such setups and only rely on a software solution if not possible through the first.
Software readouts can be off quite a lot (esp. reporting CPU/GPU temp) and consequently use improper RPM "tweaks".

Another possibility is to use temp-controlled fans, that is fans which have their own temp sensor on-board and can adjust their RPMs by themselves.
These do not require the mobo to adjust the fan voltage or use PWM to throttle the RPMs - in fact it is not recommended to use them while the BIOS fan control is activated as it may work against each other (mobo throttling using PWM, fan trying to adjust by increasing the drawn power) with the result that the RPMs stay the same.
It could even cause damage to the mobo in rare cases, I guess (if the fan is pulling more power from the fan connector than allowed).

Settle for one method first, then buy the HW accordingly!

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