JC2 benchmark results for GTX680:
1080p res, everything else max (such as 32xCSAA)
Tower: 70FPS
Desert: 85FPS
Your results are WEIRD. You got higher in the Desert slightly and much lower in the Tower. Maybe you should run those again? Either way, I'd expect even better than 95FPS at 1080p for the Desert benchmark.
*THESE results are on "HIGH" (whatever that means) but note the R9-290X is faster than the GTX770 (nearly identical to my card) by roughly 20% (quiet mode) or almost 40% (uber mode). At 1200p.
http://www.tweaktown.com/reviews/5857/amd-radeon-r9-290-4gb-reference-video-card-review/index9.html
So your TOWER benchmark at 1080p should be a minimum of 85FPS.
*I'm guessing some sort of GPU throttling however I'm unsure why. Maybe it's a driver issue.
Make sure:
1) All four CPU cores are there and running at full speed:
- Task manager (show all four graphs)
- Prime95 (run a stress test then look at TM to see if it roughly shows the CPU speed it should be.. or use CPU-Z)
2) GPU is not throttling... use any program (Afterburner?) that can monitor GPU usage and make sure it's not dropping a lot. If it's dropping from say 1100MHz down to 650MHz that's a big problem.