3 pin fan on 4 pin motherboard

KaaN10

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Jun 25, 2013
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If I plug a 3 pin fan in to CHA_FAN1 which is 4 pin will it work the same as CHA_FAN2 and CHA_FAN3, as in can I control the speeds via bios?
 

Cerb

Elite Member
Aug 26, 2000
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Maybe. It will function, but control depends on your motherboard, and they basically never document it. If you have a fan that can be used, try it. The worst case will be that it runs at 12V always, so cooling will not be compromised. If you're already using the other two channels, just swap one of them, and see if you still get speed control.

As an example, I have an older Gigabyte, and 3-pin are not controllable via BIOS settings, but software control for them works fine. Most fans don't use that much power, so unless running a high-RPM fan, you can typically split motherboard headers just fine, too, if the 4-pin is not controllable as a 3-pin (IE, two fans on one header).
 

Cerb

Elite Member
Aug 26, 2000
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Will it work? Yes. Can you control it? No. It's PWM, that's all.
Do you know his motherboard model? Have you tested it? It varies, but some allow 4-pin PWM, 3-pin (power-based) PWM and voltage, on every port. Some make 3-pin read-only. Some make 4-pin only controllable via pin 4 PWM signal. Some allow 3-pin control only on the CPU header. Etc.. Since documentation is universally poor about it, and it's not a focus of reviews, the easiest way is to install Speedfan (for monitoring, if the BIOS will control it fine), change to using that fan port, and see what can be done. If the 3-pin-only ports are controllable, the OP has some options, but it would be nice if the 4-pin could be [power] PWM controlled, as well.