Hi!
I just purchased both ArmA2 and OA via Steam, and I'm happy to inform you that OA runs w/ >35fps @ all settings maxed out except for res, which's [1920x1080, 133%-3d].
ArmA2 on the other hand runs w/ 16<fps<25 @ practically ANY settings (changing them makes very little difference). First I couldn't get the second GPU to work at all in ArmA2, until I removed the ATI/AMD CCC. Now they run ~60%, unless I max out the distance, which causes them to run w/ <50% each. The drivers are Catalyst 10.10, tried the 10.4, no significant change.
Any ideas on how to fix it? Oh btw, the -winxp parameter doesn't really help.
The rig:
Win7 x64
i7 950 (stock clocks, lol)
XFX HD5970 Black Edition
3x2GB DDR3 Corsair Dominator RAM
random WD SATA HDD for the OS - on that note, maybe I should upgrade