I have SLI enabled (in the Nvidia control panel the SLI rendering setting is set to force alternate frame rendering 2. In the Configure SLI, Surround, PhyX menu, in the SLI configuration submenu I have Maximize 3D performance checked and in the PhysX settings submenu I have it auto select), however when I look at the SLI indicator the bar is small so it doesn't seem to help much. I also play in windowed mode using a resolution of 1800 x 1000.