I'm using SLI with 2 Evga GTX 660's, and it sometimes works, sometimes doesn't. When it doesn't work, I get shaky white text at the main menu, and tons of rendering issues when playing. When it does work, it is horribly optimized and gets shit performance. I'm comparing the performance to Arma II OA. With max settings in Arma 2 and a 3d resolution set to 100%, I get no less than 40 FPS. Same settings in DayZ, I get no more than 30 FPS, with occasional drops to 20 FPS. I get better performance in Arma 3 maxed out.