Maximum resolution is not dictated by the Graphics card. It is dicttated by the maximum resolution that is supported by you monitor. When windows initializes the diplay system, one of the things it does is query the Monitor to find out what display resolutions it supports. Then it automatically chooses the best resolution for that display (usually the Monitors native resolution). While the graphics card may support higher resolutions, if windows does not get information that the Monitor can display at those higher resolutions, windows does not list the higher resolutions as available because they are, in fact, not available.