Dell P2723D 27" 1440p Monitor - Manual (Page 61)

Operating your monitor │ 61
Rotate counterclockwise
NOTE: To use the Display Rotation function (Landscape versus
Portrait view) with your Dell computer, you require an updated
graphics driver that is not included with this monitor. To download the
graphics driver, go to
www.dell.com/support and see the Download
section for Video Drivers for latest driver updates.
NOTE: When in the Portrait View Mode, you may experience
performance degradation in graphic-intensive applications (3D Gaming
and etc.).