cpu fan won't throttle

[deagz]

I recently just built a system with an Asus Sabertooth X58 and a Noctua NH-D14. The motherboard supports fan speed throttling and has 4 pin fan headers. My case fans are 3-pin and seem to throttle up and down, but I'm not sure to which sensor they are reacting to.

The problem is the cpu fans are also 3-pin and are always running at full speed. It appears that the cpu fan header does not change voltage, but only the PWM signal. I don't understand why they wouldn't support DC voltage throttleing on the CPU but allow it for case fans.

Any ideas on how to throttle my cpu fans?

 

[Triggaaar]

I've had the same problem with my Asus P6X58D-E. It has a 4-pin CPU connection, 1 4-pin Chassis connection, and 2 3-pin Chassis connections. All 3 Chassis connections (3 & 4-pin) are able to throttle 3 pin fans, but the CPU connection is not. I've moved my CPU fan to one of the Chassis fan connections and tested with Prime95. Running Prime95 my CPU temp rose while my system temp (according to Asus PC Probe II) stayed roughly where it was, and my CPU fan speed (attached to a Chassis connection) increased in line with the CPU temp.

This is not ideal, I don't think I'll ever get my CPU fan at max speed this way, but it's the best I can do at the moment, and I'm just going to use faster fans than I would otherwise need, in order to give me some leeway. The only alternative I have is using PWM fans, which is not what I want.

Silly Asus.

 

[WildW]

Depending on your motherboard, you may find an option in the BIOS settings to control the CPU fan by PWM or by voltage. . . at least, I've seen this option on at least one motherboard before.