Important note for Arma 2, it is a simulator more than a normal FPS game, 15 FPS is supposed to be playable (per their FAQ), and 30+ FPS is supposed to be good.
Also two great resources from the Arma 2 thread linked below:
- Can You Run It (just select game and it checks your machine's specs) : http://www.systemrequirementslab.com/cyri
- Free Demo Arma 2 download to test your system: http://www.arma2.com/demo/
Arma 2 System Requirements http://www.arma2.com/customer-support/support_en.html
Thread discussing Arma 2 System Requirements, has been around for years, so early part of thread is bit dated, but means most newer systems should work fine, http://forums.bistudio.com/showthread.php?72181-Will-my-PC-Run-this-What-CPU-GPU-to-get-What-settings-System-Specifications
Arma 2 testing of Hyperthreading impact, or lack, on performance http://forums.bistudio.com/showthread.php?80223-Arma-2-amp-Core-i7-Hyperthreading-Tested
Arma 3 System Requirement http://www.arma3.com/buy#requirements Note HD 4000 (the integrated graphics in Ultrabooks, Macbook Airs & similar) is listed at bottom of Minimum GPU but the CPU minimum of Intel dual core 2.4 GHz/Athlon Dual core 2.5 GHz rules out most if not all of those machines.
But the 13" Macbook Pro with Retina display would meet minimum requirements (running Win 7 in Bootcamp).
Thread on Arma 3 System Requirements, not as good as I would like, http://forums.bistudio.com/showthread.php?147391-Will-my-PC-run-this-What-CPU-GPU-to-get-What-settings-What-System-Specifications
Free Arma 3 Alpha invites see (Note they won't be available till 3/14/2013) http://forums.bistudio.com/showthread.php?147430-Looking-for-Arma-3-Free-Alpha-invites-Look-here!
Main forum for Bohemia Interactive http://forums.bistudio.com/forumdisplay.php?4-BI-MILITARY-GAMES-FORUMS