There were a few people that wanted to know what would happen if both cards were compared clock for clock.
It's recently been done, with both cards running at 1058Mhz which is the average GPU boost speed for the GTX.
Overall it seems the GTX 680 is better at 1080 resolutions, yet both cards seem very close at 1600.
http://hexus.net/tech/reviews/graphics/37209-geforce-gtx-680-vs-radeon-hd-7970-clocks/
Note the GTX680 was banched using 300.99 drivers instead of the latest though.
It's recently been done, with both cards running at 1058Mhz which is the average GPU boost speed for the GTX.
Overall it seems the GTX 680 is better at 1080 resolutions, yet both cards seem very close at 1600.
http://hexus.net/tech/reviews/graphics/37209-geforce-gtx-680-vs-radeon-hd-7970-clocks/
Note the GTX680 was banched using 300.99 drivers instead of the latest though.




