3 pin fan to 4 pin mobo connector

[Lord-Ilpolazzo]

Hi,

My motherboard, a Gigabyte GA-EP43-DS3L has a spare 4 pin fan connector which I would like to use to connect a small (80mm) fan with a standard 3 pin connector. The pinout for the mobo 4 pin connector is:

#1 2 3 4
Gnd, Speed Control, Sense, 5v

Versus the usual 3 pin fan connector:

#1 2 3
Gnd, 12v, Sense

So by connecting a 3 pin fan to a 4 pin fan connector i'm driving the fan off the speed control signal. I tried this out for a while and it did work, although the fan controller kept it at a relatively low speed, between 1100rpm and 1500rpm when the pc was put under a bit of load.

My question is, is this a safe thing to do? Am I at risk of damaging the fan controller circuitry on the mobo. I could not find any information as to what current the speed control signal could supply hence my concern. I am unsure as to wether this is simply a low level control signal intended for use by circuitry on the fan itself to control the speed indirectly, or a signal with enough drive to run a fan directly.

 

[grieve]

Is this what you need?
http://www.newegg.com/Product/Product.aspx?Item=N82E16812267003

 

[shortstuff_mt]

I've been running a 3-pin fan off of a 4-pin header for over 2 years without any problems. I think you're fine.

 

[EXT64]

Yep, they're backward compatible. The BIOS detects which is connected and compensates, or at least it does on my board.