The reason a fan rated at 750rpm runs at 600rpm on LNA is because 750rpm is running open air while 600rpm is running with grill, filter, and/or whatever else is restricting airflow.
Brand of motherboard has little to do with what kind of control the fan headers have. It's the model of motherboard that makes the difference. Many low and mid-range boards have few PWM fan headers while new top tier boards often have many.
There is no reason to not use variable voltage control on case fans any more than there is a reason they should only be PWM controlled. Is there a reason to not use variable speed control on CPU and GPU cooler fans? We did it for many years with no problems. Last time I looked NH-D14 still comes with variable voltage fans.
There is no logic in not use temp to rpm control on case fans. The logic of varying cooler fan speed based on heat is just as applicable to case fans as it is to cooler fans. Sense all CPU fan headers and GPU fan headers that I know of vary the fan speed based on heat.
Originally Posted by baii
Iirc, Asus header can control both type of fan since hasewell refresh, where asrock adapt that on skylake. The main advantage of voltage fan is probably the use of "legacy" fan like the gentle typhoon or s flex. Some pwm fan cannot stop spinning completely, where all proper voltage fan on voltage header can do(may require speed fan what not), making it semi passive. So if you run 24/7, it can slow down dust accumulation.
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Putting it bluntly, you are making a lot of statements that are not true.
There are "legacy" fans like Gentle Typhoon now available with PWM control.
While most PWM fans will not stop, it is not because they are PWM, but because their PWM control (internal) and or external) is not programmed to stop them. I think newer GPUs that turn off their fans below a certain temp are using PWM fans.
Few variable control motherboard headers and no fans I know of are designed to stop running at low voltage.
Variable voltage fans need the power off when they stop. It's not a good idea to just lower the voltage until they stop. While we can often get away with stalling fans at too low a voltage, it can cause damage.
Originally Posted by Loladinas
As I've already posted before in some of the threads PWM isn't the end all be all. With the fans I use, on the motherboard I use them, voltage control gives me both, a wider RPM range (~250-2400 vs. ~600-2400) and quieter operation. PWM clicks at low speeds, but I believe that's a quirk of my motherboard.
It is not a PWM versus variable voltage.
It is all what combination of components works best.
What controller is used (motherboard or independent).
Some are much better at PWM, some are much better at variable voltage, and some are not good at either.