Controling cpu fan speed

[error8]

Ok, so just changed my amd mobo and cpu and installed my old Thermalright Ultra 90 heatsink with two 92mm fans, in push-pull configuration.

My problem is that these fans are connected to my Msi P35 mobo, through the 3 pin connector, where the mobo has a 4 pin cpu connection. So the result of this is that both fans are running at full speed ( 2500 rpm ) no matter if the smart fan is enabled in bios, creating the loudest noise I've ever heard.

Does anyone know how to enable smartfan somehow? I'm keeping the fans connected through my PSU molex now and this spins them slow enough so I can hear my self thinking, but I want my old Asus M2n-E up and down fan speed style, according to temperature.🙁

 

[Zepper]

You should find the settings for any available CPU fan control in your BIOS settings (and in the monitor utility provided with the mobo). There should be at least some level of control thru the first three pins of the 4-pin CPU fan connector (those are just the same as any fan connector you just have the extra PWM control pin. you can get a 3-pin Y cable out there so you can have both fans connected to the CPU fan header on the mobo, but you will have to remove one fan's yellow (or whatever color its fan speed wire is) from its three pin connector and tape it back (or you could cut away the yellow wire from one side of the Y on the adapter) as you can have only one speed sensor wire connected to one header at a time. I hope that helps. What are those fans anyway, and why would one want 2500 rpm fans for CPU duty anyhoo?

.bh.

 

[error8]

Well both fans are connected as you say. The black and red cables from the second fan are soldered to black and red of the first fan, yellow cable of the second is not connected. The thing is that I can't control their speed at all through the cpu 4 pin connector, not in bios not with the utility. They just run at full blast.
The stock intel cooler worked normally with the 4 pin connection, running faster or slower, depending on the temperature.

I don't know what type of fans are, since nothing is written on their boxes and having 2500rpm wasn't a noisy deal since they ran very rarely at full speed on my old Asus.

 

[Operandi]

4 pin PWM fans are not the same as your average 3 pin fan. When your motherboard controls a (4 pin) PWM fan the 4th wire (PWM) is the signal wire that tells the fan what speed it should operate at per your BIOS or software settings. The PWM control IC is actually built into the fan itself not on the motherboard which is why your 3 pin fans are running at full speed.

Having said that some boards still have the hardware onboard to control 3 pin fans but its really more of an option than a standard feature. It should be documented in your motherboard manual if your board has that feature and like Zepper mentioned there will be a BIOS option to enable control over 3 pin fans vs. PWM fans if your board supports it.