DisplayPort settings of the LCD display may limit resolution

The DisplayPort settings of the LCD display may need to be configured to achieve maximum resolution using a DisplayPort connection.

DisplayPort connected display doesn't show Optimal Resolution.

Your Dell 4k or 2k Ultra HD display may report that the maximum resolution offered for the display is less than 3840 x 2160. The highest resolution obtainable may show as WQXGA 2560 x 1600 pixels.

This can occur when the display is correctly connected using a DisplayPort cable without adapters.

Configure DisplayPort 1.2 in the display configuration.

To ensure display resolution higher than 2560 x 1600 pixels, configure DisplayPort input to DisplayPort 1.2 in the On-Screen Display (OSD) settings of the LCD display. For information on changing the OSD settings for you Dell LCD display, reference the display manual at the following location: Dell Support / Manuals.