I have a LG 29UM58 which runs at 2560*1080. My ATI FirePro V4900 only allows 1920*1080 on the ultrawide monitor. The ATI FirePro V4900 works fine with DELL 34 inch ultrawide with 3440*1440, but I don't understand why it cannot work with the 29 inch ultrawide with a lower resolution. I have tested the video card on two different computers, on both windows 7 and windows 10. I have tried the Custom Resolution Utility (CRU). I also tried the manual regedit method from here. None of those can make the 2560*1080 resolution on the LG monitor and it's always 1920*1080. I also tried to add custom resolution through AMD Control Center, but it says 2560*1080 is not compatible with the monitor.
The monitor works fine with other video cards. I just need to make it part of three-monitor solution through V4900.