Fan speed + LNA + PWM

Dogway · 26 Nov 2013 at 18:45

LNA cable necessary for PWM fans?

Hello, I would like to know if using the LNA cable of the noctua makes sense if I can either way cap top speed via "thermal radar" software. Also it will be plugged into a CHA_FAN header which I have read isn't really PWM, is that true?

I also want to ask if do you recommend intake being at max all the time. I have a Prodigy M with the 230mm fan at bottom as intake (3 pin) and I would think it's better to modulate it via thermal radar as well and a thermal graph, but I have been advised to leave it at top speed...

Thank you

Dogway · 27 Nov 2013 at 17:44

Maybe I should reformulate my question.
If I can control fans via software (via temp graphs, cap max speed, etc), why would I need PWM fans or LNA cables?

abbotsmike · 27 Nov 2013 at 18:08

If you are wanting to use the software control, then you don't need the adapter cables. They are generally just a resistor, lowering the voltage to the fan.

PWM fans depend on the fan header. If the software controls the fan speed via pwm, then you need PWM fans.

Dogway · 27 Nov 2013 at 18:17

I see, that would mean that 3pin fans can't be self regulated by any means?

If I were to only cap max speed on a fan, which of both ways would be preferred, using the LNA cable or via software? I would think using the cable is a bit more of an elegant way, but don't know.

Tealc · 27 Nov 2013 at 18:34

Not all motherboards or headers can regulate the speed of 3 pin fans. LNA is a quick and easy way to drop the speed of a fan to perhaps more tolerable levels.

You can use LNA as well as PWM control (assuming 4 pin fan and a 4 pin LNA) to lower the top end speed the fan can reach at maximum duty cycle.

Regarding fan speed. It makes more sense to have less airflow when you pc is idle and more when it is busy and getting hot, that's where motherboard voltage and PWM control come in, although some fan controllers have rudimentary temperature control based on stock on thermistors.

Dogway · 27 Nov 2013 at 18:54

So everything comes down to the motherboard? mine is an Asus Gryphon, I think it uses the software thermal radar (I still havent finished building the rig). I think it's a fine board so I would bet it can regulate 3 pin fans, I hope.

I have also a noctua with 4 pin LNA cable, I like "fixing" things in hardware first, it makes more sense, you put a resistor and that's it, but it might not matter, I ask. Then I can set up a profile in BIOS or via software on top I guess.

The problem with the Gryphon is that on the guidebook it talks about installing some "thermistor sensors", but this kind of board should come with internal sensors bundled, right?

ubersonic · 27 Nov 2013 at 22:12

If you have a decent ASUS board just use the Qfan software (can be setup in BIOS or in O/S via ASUS Ai suite) to control 3pin fans via the chassis headers.

foster grant · 28 Nov 2013 at 09:45

Cant you just use a Fan Controller ? I wouldn't use that ASUS AI Suite

Dogway · 28 Nov 2013 at 10:45

Yes, I don't like using intrusive bloated software in background either but it seems to be a necessary evil.
By Fan Controller you mean a rehobus? I really don't want to bother with fans once set, I just need them to run according to load/temps. Also my 5.25" bay is occupied with a burner. I found yesterday this nice page explaining everything very detailed about Asus boards and their fan management. It says that in Windows the software overrides the BIOS settings, but till then (Windows loads) management is under BIOS.

I'm still left with the question of what role a LNA cable plays in this scenario where everything is controlled by software.

abbotsmike · 29 Nov 2013 at 03:37

AI Suite is quite lightweight, certainly doesn't cause any slowdown here, and IMO, works pretty well. You also don't have to install the whole suite. I've only got fanxpert installed!