Ok I noticed when playing DayZ especially when in big city's or on maps like lingor island my fps would dip quite a bit and not because I didn't have enough GPU power most of the time my gpu is sitting around 50 percent and the highest I ever saw was 80 and I still noticed I couldn't keep solid 60 fps an sometimes it would get as low as the 30s. Anyway long story short I went into driver settings and changed the pre rendered frames from use game defaults and set it to 1 and Arma II runs a HELL of a lot smoother now and it tripled my friends fps who uses a Phenom II x6 with a 570. So....I would def give it a shot and see how ya make out. This made a huge difference on a i7 3770k so if your using an even slower CPU you will notice much improvement. edit: ah **** I thought I posted this in the drivers section.......
keep your native or what ever resolution but turn down the 3d resolution in video setting and set to high performace mode in nvida settings