You can change the screen resolution temporarily as a test to determine if the monitor supports the specified resolution.
Do not change screen resolution while the window system is running. Changing screen resolution while the window system is running may put the screen display in an unusable state.
Use the afbconfig command as follows:
afbconfig -res video-mode try
See Table 7-2 for the list of video-mode options (see the "Video Mode Format" and "Symbolic Name" columns in the table). You will have five seconds to confirm the video mode by typing y.
This changes the resolution to 960 x 680 at 112 Hz stereo the next time Xsun is run.