Originally Posted by McMogg
The HD7970 runs hotter than the GTX680
Taking the PCS 7970 (reference) and the nVidia GTX680 (reference) out of that graph, it's clear the GTX680 runs a bit cooler, meaning the chance that the 7990 will be two 7970s at the same clock is lower - as the heat output would be too much.
Also, the GTX680 is faster than the 7970, seems as the 690 performs like 2x680, it's rational to assume it will beat the 7990.
but, if you had more money than sense, I'd try them both and resell the loser.
Those temperature results only show how effective the reference cooler is at disappating heat. That doesn't show the actual heat output. Both cards are roughly within 25w of each other. Meaning they both output roughly the same amount of heat. So 7990 will more than likely perform roughly equivilant to 2x 7970's in crossfire.
With the above in mind, we can assume that 7990 and 690 will more than likely trade blows back and forth, just like the 680 and 7970 do. They're VERY equivilant cards this round.
As such, there really is no for sure winner yet, since the 7990 isn't released yet. My guess is that they'll perform nearly identical to each other. So it comes down to the resolution one is planning to run. If you're running more than 2560x1600 resolution (in other words Eyefinity or Surround), I'd wait for the 7990 as the 2GB vRAM of the 690 will choke. If you're at a single screen resolution....well I see no reason why you'd even THINK about going for quad GPU's. So in other words, I'd grab the 7990's regardless.