Eu mesmo não consigo testar, mas achei isso:
Requirements for high resolution display devices:
If the required resolution is 2560x1600 pixels (such as running on a 30” display), the following conditions must be met:
- The monitor and graphics card must be connected with a Dual-Link DVI cable.
- The graphics card must have a Dual-Link DVI port.
Note! If these requirements are not met, the maximum resolution will be limited to 1280 x 800.
Reference: http://support.amd.com/en-us/kb-articles/Pages/GPU-10-SupportedResolutionsUnavailableforMonitor.aspx