By chance, do you use two of these... side-by-side?


From: DJ Delorie <dj@delorie.com>
To: Community support for Fedora users <users@lists.fedoraproject.org>
Sent: Monday, April 29, 2013 12:40 PM
Subject: Re: 3840x2160 resolution?

$ xdpyinfo | grep dimensions
  dimensions:    6880x1600 pixels (1818x423 millimeters)

That's four monitors on an ATI Radeon HD 6870 card, with proprietary
drivers.

Note: my solution to the widescreen monitor problem is to rotate them,
making them tallscreen monitors instead.