Newb Fan Header Question - ASUS P8Z68V-LX

[teddyv]

Hi Folks,

I recently put together a new system using an Antec 300 case and an ASUS P8Z68V-LX motherboard. The last system I had was c.2005, an Epox AMD 64-3000 system using an Antec Sonata case where the case fans hooked up to the Molex connectors and had individual L/Med./Hi switches.

I worried a bit about the temps of the hard drives on the 300 so I bought a couple Corsair 3-pin 120 case fans to add to the front. Install was a breeze and I simply used the molex converter to hook them up to a handy molex connector but MAN is this thing loud now with both fans blowing at max speed. I re-read the manual and thought I might use Fan XPert to control the speeds as the case is pretty cool and the 100% max 100% of the time is a bit overkill. That said, the two CHA_FAN headers are 4-pin - so I had a few questions...

1. I know I can hook up the 3-pin to the 4-pin headers, but will the P8Z68V-LX be able to modulate the speed of the fans or will they still run at 100%? There seems to be some conflict whether the fan speed can currently be modulated, I guess by voltage, or whether it is just 100%

2. Can I use a splitter to run the two front fans from a single header? I read another thread that doing so would work fine as long as one of the two RPM fan leads to the splitter cable was snipped and taped to ensure correct RPM reading. Is this correct?

3. On the ASUS boards I read that there is a new version of Fan Xpert coming out that will be able to recognize and control 3-pin fans I guess into a 4-pin CHA_FAN header. Anyone heard of this?

Ideally I would like to buy a splitter and hook the two added 3-pin front case fans into a splitter, plug that into one of the 4-pin CHA_FAN headers, and have the ASUS fan program automatically control the speed depending on the temps inside the case. Can this be done or should I just toss the 3-pin fans and invest in 4-pin ones?

Thanks!

 

[mindless1]

1. I don't know about that board but some boards can vary speed on a 3 pin fan plugged into 4 pin header, but it can be a bit fiddly to get a good setting if trying to make the fan ramp up in RPM with temperature. Try it and see, there may be bios options. It's possible not all fan headers are bios controlled or controllable at all, you might need an extension cord to plug into a different header.

2. Yes you can run two from one header. In theory two very high powered fans could exceed the current capability of the header but I doubt the fans you bought use enough current to matter. Keep in mind that there may be a change in RPM doing this, depending on how the control is designed.

3. Do you have air conditioning? If so, your case front intake should be low enough in temperature that you don't gain much having varying fan speed based on temperature. Personally what I'd do is just solder in a power resistor to make it the speed you want without having to depend on where it's plugged in or what's controlling it, especially in the case of software, what if your system were to lock up in a 100% busy loop creating more heat but the software isn't responding to raise fan RPM?

About the power resistor, usually I use something about 68 ohm to 100 ohm. The lower current the fan is the higher ohm the resistor should be (somewhat counter-intuitive) so sometimes the value is as low as 33 ohm or as high as 150 ohm. >= 1W power rating.