i dunno man people have been over-blowing the difference between AMD heat output and Nvidia heat output for a long time now. from my experience 6970's put out more heat then a GTX 570 or 580 and run about 10 degrees hotter compared to the 570's and 580's as well. So im not surprised. also it is virtually impossible for the fan on the 590 to be louder then the 6990... it's larger and uses a much more efficient design and will move more air effectively.
people kept going on about how it was impossible for Nvidia to pull it off.... now look full dual 512 shadder parts on the market tomorrow and it's smaller and probably quieter then the 6990 to boot....
what it will come down to will be the OC potential or this card. it it can get to 730ish MHZ it will beat the 6990 by a good margin provided your not running 3x30 inch monitors....
Bookmarks