Low-speed or high-speed GTs?
Neither can be controlled out of the box but you could attach a fan connector to them instead of the molex connector. Or make a fan connector that plugs in to the motherboard header and then goes to a molex connector to which you hook up the fans. Don't connect too many fans on 1 header though (you should check your motherboard manual to see the max Amperage it can deliver. Fans use more Amperage at start-up)
Your motherboard should have an option to regulate the fans via voltage that way, or you could attach them to a fan controller.
If you have the high-speed GT (AP-29, 30 or 31) then read on. I would strongly advise against hooking them up to the motherboard because they pull too much power.
So if you have the high-speeds then there's something else you can do which is actually a better solution IMHO.
PWM mod: http://www.overclock.net/t/1045524/gentle-typhoon-pwm-mod
This will basically make your fans PWM fans. It's easy to do and works flawlessly. I currently run 3 this way. Keep the power lines on the molex to not stress your motherboard.
A few notes:
I don't know if there's a limit on how may times you can split a PWM signal but I currently have it split 4 times (3 Scyhte GTs and 1 MCP35X) and no problems whatsoever.
When connecting them to a single PWM header on the motherboard only allow 1 RPM signal to return to the motherboard otherwise you'll see insane fan speeds ^^ ( motherboard just adds them up).Edited by Bloitz - 2/26/12 at 2:41am