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Asus M5A97 R2.0 PWM Chassis Fan control??

post #1 of 8
Thread Starter 
I posted this in air cooling but I thought I'd spread around the knowledge pool a little thinking not everyone visits every forum...

I've an Asus M5A97 R2.0 motherboard which has three 4 pin chassis headers and one 4 pin cpu cooler header. These headers are clearly PWM/RPM/12v/ground as shown in the owners manual. I purchased four Xigmatek XAF-F1255 120mm 4-pin pwm fans for CPU cooler and Chassis front panel and rear exhaust. I also got two Xigmatek XAF-1454 140mm 4-pin pwm fans for chassis bottom inlet and top exhaust. I used two Rosewill RCW-FPS-401 3-way pwm splitters. I wired the three 120mm chassis fans on fan header 1, the 120mm cpu fan on cpu fan header, and the 140mm chassis fans on fan header 2. The splitters are hooked up correctly - one fan is plugged into the "cpu fan" lead with 4 pins. The 2 wire pwm and rpm feedback lead is plugged into the mobo, and naturally the molex connector is attached to PSU molex. with this arrangement the fans on the splitters run at 100% no matter what. If I use one of the splitters with the CPU header, all fans on that splitter are speed controlled as they should be. I checked bios and FanXpert to try to find a way to select voltage control or pwm control but could not. I even downloaded SpeedFan to try it. When I plug the fans directly to the mobo chassis fan headers, the speed is controlled but I'm not sure if it's varied voltage or pwm. While looking into it last night I also found out that the Asus minimum speed on chassis fans on manual mode in the bios is 60% which seems to be a standard or some sort, which is really not low enough at all. For now I have the CPU and two front fans on the CPU header via one of the splitters and the rear fan on header 1, top fan on header 2 and the bottom fan is on the splitter via header 3 but it's on at 100%.. I'd just plug it directly but the cable is too short.

So, I guess I have a couple of options... A, get this issue resolved and have it run the way I originally intended, B, simply purchase an extension or make one out of the splitter to get the bottom chassis fan on the header and have the fronts cpu speed based and the others chassis speed based, or gang them all on the cpu speed signal to make use of the lower 20% setting. I will say this is a huge improvement over the stock 3 fans... motherboard temps down by about 10c, cpu down almost 10c while playing bf3 (my "under load") and GPU is down almost 10c while playing as well.

Anyone have any ideas or suggestions?
post #2 of 8
I'm guessing you have the 3 way splitter that connects to Molex for power, i have a couple of these, and they just don't work, even though they have a 4 pin connector to get PWM from the board, they always run at 100%. I have the M5A97 R2.0 as well, but i'm having issues with the #1 chassis fan header running at 100% and the others being speed controlled just fine, have you seen anything like this?
post #3 of 8
Thread Starter 
The speed control works fine with the splitters when used with the CPU fan header. Just not the chassis fan headers. No idea why your no. 1 isn't modulating.
post #4 of 8
Very strange, i'm on my 3rd one, so it's probably not just a board defect, the ASUS customer service person i talked to seemed to think it was just the bios, i'd say even stranger that you're getting that splitter to work on one but not the other, It's a great board at the price so i really hope this all gets figured out.
post #5 of 8
I also have the Asus M5A97 R2.0 board, and I'm trying to use SpeedFan version 4.49 (the latest) to control fan speeds. I've also tried 'Fan Xpert" to no avail. I'm using the latest BIOS (1903).

The only fan header I can control with any OS software is CHA_FAN2. For this to work, I have to disable the "Quiet n Cool" features in the BIOS, but leave the individual fan speeds monitored. At that point, upon boot, all fans run at 100%. Once I boot in to Windows 7 and start Speedfan, I can adjust CHA_FAN2, but not CPU_FAN, CHA_FAN1, or CHA_FAN3.

I also find that in the BIOS and in Windows 7, the motherboard can misreport RPMs, where the reported RPM will jump from 2000 RPM to 54000 RPM and back in less than a second, over and over again. One the misreporting starts, the only fix is to power off the system completely.

If QNC is enabled, the fans are quieter, but not near as quiet as they could be while still properly cooling the system.

The 4 fans (3 with 3-pin female connectors, the GPU fan with a 2-pin female connector) are behaving as such:
- GPU fan: doesn't report RPM, but responds to Speedfan controls.
- CPU fan: reports RPM, but doesn't respond to Speedfan controls.
- 2 120mm case fans: report RPM, but don't respond to Speedfan controls.

All the headers look the same (having 4 pin male connectors). Speedfan could control the CPU and case fans when each was connected to the CHA_FAN2 header. Connected to any other fan header, it could not.

My experience with another PC (all fans having 3 pins), is that all fans are controllable with Speedfan, and connected to sensors named Pwm1, Pwm2, etc. I'm learning that Pwm fans have 4 pins, and maybe this ASUS board's headers can ONLY control Pwm fans. However, I don't understand why CHA_FAN2 would be able to control the speed of any 3-prong fan plugged in to it, while the other 3 fan headers can't, being CPU_FAN, CHA_FAN1, CHA_FAN3.
Edited by KentuckyThrash - 8/26/13 at 3:24am
post #6 of 8
I ordered 2 Pwm fans, an 80mm and a 120mm. I guess I'll find out if the other fans being non-Pwm is the problem. If so, I can control the new 80mm with CPU_FAN, the new 120mm with CHA_FAN1, and a 3-prong 120mm with CHA_FAN2.
post #7 of 8
It seems that while the motherboard has 4 pin connections for the case fans and says it supports PWM fans, it treats them as 3 pin fans. That's why the lower limit is 60%, to insure enough voltage to start a non-PWM fan up. (60% of 12 volts is 7.2 volts).

As 60% at a minimum is way too high, I went with the following solution:

First, for the case fan connectors, I used "silent" fans that at 60% are basically silent. Secondly, I got a 4 PWM fan splitter which I plugged my 2 CPU fans as well as 2 other PWM fans into and plugged them all into the CPU port on the motherboard.

This way, I have silent fans drawing air in and out of the case, but have 4 fans that are tied to the temp of my CPU and go all the way down to about 20% speed which is near silent.

This was a near necessity as I have two 120mm case fans that each do 100CFM and at full speed are not exactly quiet. At 20% they make little noise. But, if things get heated up, they can really kick in.

Also, the advantage of doing this is that I can use the stock ASUS BIOS to control the speed of all the fans.

It's too bad that while the motherboard says it supports 4 pin PWM fans it doesn't really work well. But, I understand why. Most case fans are 3 pins and they need to insure there's enough voltage for them to spin up. Really, they should correct this by allowing a PWM/voltage switch in BIOS per fan port. But, it was only a $90 motherboard and there's an inexpensive fix for it.

Tim
post #8 of 8
I have the same board and the #1 chassis fan header runs at 100 percent all the time. So, that was actually handy because I have a Corsair H60 liquid cooler and I hooked the pump up to that header.
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