Three options, of which uh-no has already posted one. Fans directly from a Molex will run a full speed always. Second option is to do that, but buy also a "fan speed controller" box you insert between Molex and fan - it allows you to reduce the fans' speed to some fixed setting. Third option might be to run TWO fans off one mobo pinout - but NO MORE than two - with some wiring adjustments. Assuming you have two 3-pin fans and one mobo pinout, modify the fans' wiring. Splice / solder / tape up the two fans' RED leads together, and the two BLACK lead together so that they both are powered from the one connector. Do NOT splice together the yellow leads - leave one disconnected and taped up. This will power both fans the same, and feed back to the mobo the speed of the one fan whose yellow lead is still connected. (The other fan's speed will never be known.) Most mobos appear able to power two fans in parallel like this, but three is questionable, especially for the start-up surge current.