I have a new nVidia GTX 560 based card and an older GTX 260 card. I have a single 2560x1600 monitor on the 560 (center of my desk) and two 2560x1600 monitors on the 260. (to the left and right of the main monitor) The 560 monitor is marked as the main display. This gives a single desktop of 7680 x 1600 using normal (2-D) desktop applications.
I see pictures of gamers running a single game across two or more monitors. How can I enable this? Right now I just use the center monitor. The works fine most of the time, but I'd like to try running games at the full 7680 x 1600 as a test.
EDIT: I am not running SLI due to the limit of only two monitors. From the SLI FAQ:
With GeForce R180 drivers (or later), standard SLI configurations for 2-way, 3-Way, and quad SLI support a maximum of two monitors. Additional monitors (up to 6 monitors total enabled) may be enabled by using either a motherboard GPU and/or a PhysX capable graphics card (GeForce 8 series or higher with at least 256MB of memory) that does not have the same GPU as those that are SLI enabled.
I'd be willing to get another GTX 560 and set up SLI, but it doesn't sound like this would help my desired setup of 2560 x 1600 (x3) - unless I'm misunderstanding the FAQ.