This is how the 590 should have been from the start. Nevertheless, mars II is the current king of dual gpu's. Its beats both 6990 and 590 by a big margin. Even the 580 sli is no match for this beast.
The 590 also beats the 6990 in most games thanks to improved drivers.
Source
The 590 also beats the 6990 in most games thanks to improved drivers.
Source