I recently bought ArmA 2 Combined Operations off Steam (auto-updated by Steam). To my disappointment the game doesn't run that well on my rig. According to FRAPS my FPS are mostly varying between 18 (in towns) and 23 (i.e. in heavily wooded areas) in Chernarus map. With view distance around 3000m there's no notable difference between playing with all graphical settings on "Very low" and "Very high" (except for the eyesore of course), same goes for resolution/3D resolution. If I lower view distance to 1000m I gain a few FPS and if I set it around 5000m I loose about the same amount. This leads me to believe that there's either something wrong with the game or with my system.
CPU: AMD Phenom X6 1035T (Hexacore at 2,6 GHz each)
GPU: XFX ATI Radeon HD6870 Black Edition 1GB DDR5 (Overclocked to 980/1150 at stock volt) with ATI Catlyst 11.1a Drivers (most recent)
RAM: 6GB (2x3) DDR3 at 666 Mhz (low speed but shouldn't matter while gaming)
PSU: Corsair 650W 80+
Motherboard: Acer... (= locked BIOS...)
Soundcard: RealTek onboard
HDD: 1TB 7200RPM
OS: Windows 7 Premium Home Edition 64-bit
Screen: Sony HDTV 40''
I've also added ACE 2 which didn't have any impact on FPS whatsoever. The past week I read most of the "optimization guides" out there and tried messing around with the .ini but to no avail. I've tried different parameters (both manually and through launchers) like -maxmem 2047 (which ArmA 2 doesn't even seem to care about), -winxp, -cpucount 2-6, -exthreads 1-7 etc. I'm also running the game, the launcher and Steam as an administrator. Neither has had any notable impact on the game.
VSync is off (forced by Catalyst Control Center), everything in CCC is set to performance, both CPU/GPU shows the right "clocks" in CPU-Z while running the game. CPU and GPU temperatures are within their usual limits.
I'm aware that my CPU isn't top of the line and that ArmA 2 doesn't take advantage of all six cores. May this is what's bottlenecking my performance in ArmA 2? Would upgrading to a AMD Phenom X6 1090T (Hexacore at 3.2 GHz) mean a massive performance boost?
Any help in resolving this frustrating matter is greatly appreciated!