Can't find a 1680*1050 résolution

Hello

After a power failure when we started  the 2 DeltaV Workstation xp  (Dell R5400 with ATI fireGL 3750 graphic adapter)  the screen resolution was lost.

 After trying the following steps: 

  • Using all available resolution 
  • uninstalling and installing graphical diver 
  • Replacing one of the FireGL 3750 driver with a FireGL 3600 and installing it's driver 

The best thing we have got is a full screen display with gray border (1770*1000) as shone bellow.

 

 

We did not find the best resolution for a 16/10 ratio even if we tried changing with the driver program

.

I will be thankful if anyone can guide me to go through this problem