Asus Z97-A PWM & Corsair Obsidian 750D

[Nuluvius]

Given wanting to use the stock fans that come with the Corsair Obsidian 750D with Asus Z97 - A motherboard fan headers. Will these respect PWM?

I am aware that the headers on these latest motherboards are not PWM despite having four pins. They seem to use voltage to control RPM instead.

For that matter, will these headers be able to do a good job at controlling other PWM fans? I know Asus likes to tout its FanXpert software a great deal...

 

[BleedingEdgeTek]

PWM isn't necessary, but no, the fans that come with the 750D are 3-pin.

 

[Nuluvius]

PWM isn't necessary, but no, the fans that come with the 750D are 3-pin.

Thanks, just to clarify are you saying that the stock fans cannot be ramped up/down using Z97 4 pin board (any board manufacturer) headers?

 

[BleedingEdgeTek]

No, they can be adjusted, just not through PWM. They can be adjusted via voltage control.

 

[Nuluvius]

No, they can be adjusted, just not through PWM. They can be adjusted via voltage control.

Yeah that's what I had suspected. Do we know how well this functions?

 

[BleedingEdgeTek]

It works just fine for me. Really the only difference is the minimum starting speed, which is around 25% usually for PWM and about 35-40% for voltage regulated, depending on fan. But as long as you get good fans which aren't loud to begin with, there won't be any noise difference. I use voltage-regulation to control my 3 intakes and 1 exhaust. Being all Noctuas, I leave them at 75% (not audible from more than 6") and only have them increase when my GPU temp gets above 50c, which only happens in gaming.

Voltage control isn't as precise as PWM, but for case fans, it really doesn't matter in the end.

 

[Nuluvius]

This is causing me some concern you see :/

http://forum.corsair.com/v3/showthread.php?p=710824

I'm guessing that they certainly won't start up from a cold boot as the temps would not be high enough to warrant a 35-40% ramp up. Only after some time operating would temps get high enough to signal an increase thus starting the fans.

 

[BleedingEdgeTek]

The 'not starting up' is most likely Fan Expert trying to start them at too low of a voltage. My MSI board does the same thing with my Noctuas. You can change this in the BIOS for them to start at about 40% instead of 25% or whatever.

 

[Nuluvius]

The 'not starting up' is most likely Fan Expert trying to start them at too low of a voltage. My MSI board does the same thing with my Noctuas. You can change this in the BIOS for them to start at about 40% instead of 25% or whatever.

Yeah exactly that, it's a configuration issue at the end of the day. Rectified as you say, by setting the base tolerance to just enough to kick the fan off.

 

[BleedingEdgeTek]

Yeah lol I was just about ready to RMA all 3 Noctuas I had up front, then realized 'wait, there is NO way I got 3 bad Noctuas at the same time' lol Then remembered with voltage control, most fans need around 40%, and MSI had it set to 25%.

 

[Nuluvius]

I don't think there's nearly enough documentation on modern fan control methodology to be honest. Certainly the advertising glosses over the fact that MB headers are actually voltage regulated. There's only two true PWM signal headers on the boards; the main CPU fan header and the CPU OPT header.

Indeed one could well plug in a splitter and daisy chain the PWM signal around their case. However doing so only gives you PWM in the context of the CPU and NOT the individual temperature sensors located around the board. So in that respect it ends up being pointless and even detrimental for case fans; imagine the scenario where the GPU or the chip set gets hot ahead of the CPU.