Did you try a system reboot and then run Heaven again. I got strange behavior a couple times with Heaven if I alt tabbed out of it running full screen and then went back in , resumed full screen. Noticed my loading on dual gpu's was less and uneven. This is in a Nvidia SLI setup. I keep a OSD of the two gpu's and their load #'s in the corner of the screen. Anyways, by happen chance, it was about 10% less performance. I was definitely getting the benefit of both gpu's VS just 1, but it was 'off' Thats not something I would notice in gaming obviously, maybe in another timed/scored benchmark.