Intel HD 4000 for OS X + unsupported Ati R9 290 for Windows?

[Cinner]

I currently use my integrated Intel HD 4000 graphics for OS X, but would like to install an Ati 290 for gaming under Windows. The 290 is not supported, and I have read some reports that this means its fans will run at 100% all the time and it will probably be running at full power usage as well? Is this the case in Mavericks also? I mean I know it is still unsupported but can the card at least power down to an acceptable state?

 

[Cinner]

I bought a Sapphire R9 290 Tri-X and the fans don't spin at 100% in Mountain Lion or Mavericks. They do spin a little harder than when the card is idle under Windows, thus making slightly more noise and presumably using more power.