Have my new 21.5" iMac attached to an external monitor via hdmi. The external monitors resolution is 1920x1200 but the only display options for it in os x are 1080p and 1080i which obviously have a vertical resolution of 1080. According to AMD's site the gpu supports a maximum resolution of 1920x1200 through hdmi. Also, I am not mirroring the displays. This monitor's native resolution was supported on my first generation macbook pro--this is getting very frustrating, does anyone know what the problem could be? Does anyone have a similar setup that works?