I bought a XFX Double D FX-787A-CDFC Radeon HD 7870 and set it up using the HDMI, DVI and Mini DisplayPort (using an Apple mDP-to-VGA adapter). I hooked it up, installed the drivers and rebooted. The image came up on the third monitor in a weird resolution. Why did this happen and how can I fix it? I am using Windows 7 Ultimate and the system is completely updated.
Side note: When I disconnect the Mini DisplayPort adapter it works fine, however for my work I need 3-4 monitors.
Best Answer
I'm not sure if this will help, but the Eyefinity how-to page indicates that your first two monitors can connect with any display output (HDMI and DVI, in this case), and your third monitor must be connected via the DisplayPort.
Now, you say that the third monitor (presumably the one hooked up via the mini displayport to vga connector) came up in a weird resolution. You don't mention what resolution this is, though. Apple limits the maximum resolution to 1920 x 1200. I'm guessing that's at 60Hz, too. If you are trying to go higher than 1920 x 1200 at 60 Hz, or higher than 1600 x 1200 at 85Hz, you may want to lower the resolution or refresh rate.