BIOS does not detect fan speed

blake · Post by **blake** » Thu Jul 12, 2007 10:23 pm

I have an Asus P5N32-E motherboard and Noctua S12-1200 fan. The fan has a 3-pin connector. When plugged into the motherboard, the bios does not detect fan RPM, nor does SpeedFan? The only fan detected is th cpu fan.

The mobo manual states that the connector the noctua is plugged in (CHA_FAN) and OPT_FAN1-3 can be "q-fan" controlled, which i assume implies it can monitor/adjust fan speed?

blake · Post by **blake** » Thu Jul 12, 2007 11:23 pm

How strange.. After a few reboots the BIOS (and Asus probe II) detects the Noctua (chasssis) fan speed. But it is reading 1000RPM (not 1200)?? I am NOT using the ULNA, and the "duty cycle" is set to 100% in the BIOS?

blake · Post by **blake** » Thu Jul 12, 2007 11:43 pm

Yet another reply to myself!

Did some detective work on asus.com:

Q: My chassis fan seem to run slower when connected to CHA_Fan1 connector even when I set the fan to operate under Duty Cycle Mode.
Is this normal?

A:This is because CHA_FAN1 connector has been specially designed to force fan to operate at 30% lower RPM under full run, in order to reduce overall system noise. As this motherboard comes with 6 chassis fan connectors in total (CHA_FAN1 & OPT_FAN1~5), please connect your chassis fan to OPT_Fan1~5 if you desire to allow chassis fan to operate at 100% RPM under full run

However, connecting to another mobo header (OPT_FAN3) runs my fan at 1300RPM at 100% duty cycle (not 1200rpm). Must be supplying more than 12V?

McBanjo · Post by **McBanjo** » Fri Jul 13, 2007 1:36 am

My Noctuas run at 21093rpm according to Asus A8N-SLI Premium

Not sure if the fancontrollers on motherboard still sucks or it's something up with that fan

Das_Saunamies · Post by **Das_Saunamies** » Fri Jul 13, 2007 6:03 am

Same thing here blake. 1300 RPM when I close my Sonata II if at full blast from mobo or the fan controller(see sig). For me it's the pressure doing it, although I think the fans are configured to be able to run just over the 1200 RPM mark as a precaution of sorts.

The readings go erratic if I use the ULNA adapter or two consecutive adjustments(mobo+fan mate 2). It's just the way they are it seems.

cloneman · Post by **cloneman** » Fri Jul 13, 2007 7:26 am

As I've seen many boards are unable to give you fan speeds on very low RPMs. If your noctua is getting the full 12V it should be able to read it, but if your board is providing less than 12V (now common for quietness purposes) your noctua may be falling below the rpm the board is able to read.