(TL;DR See the last paragraph for how to get the Dell U2713HM working on the HDMI output of the Acer V3-571G at 2560×1440 @ 50Hz.)
The Dell Ultrasharp U2713HM is a 27″ IPS panel with a resolution of 2560×1440. I recently acquired this monitor and wanted to connect it to my Linux-only Acer V3-571G i7 laptop, which only a VGA (D-SUB; max resolution 2048×1536) and an HDMI 1.4 output.
HDMI 1.4 does support 2560×1440, but the HDMI 1.3 input on the Dell U2713HM does not. (The HDMI 1.4 input on the more expensive Dell U2713H does.) This means that we have to use either the DVI or DisplayPort inputs.
For 2560×1440 at 60Hz refresh rate, normal single-link DVI is not sufficient. One either needs dual-link DVI, which I don’t have, or one can use a cheap HDMI to DVI connector and tweak the timings of normal single-link DVI to supply 2560×1440 at a frequency that is as close as possible to 60Hz, but still fits within the available bandwidth.
Part of this tweaking is making use of reduced blanking, an optimization that can be done on LCD panels where there’s no electron beam (as is the case in CRTs) that needs time to be repositioned. In short, we can squeeze out more resolution and refresh from the same bandwidth.
NotebookCheck has a wealth of information on tweaking these timings. Unfortunately, the configuration they supply for 2560×1440 at 55Hz only caused flickering on my setup.
Fortunately, Linus Torvalds (just some guy who seems to know quite a bit about Linux documented on Google+ his adventures getting such a monitor going under Linux, albeit with a 30Hz refresh rate. Fortunately, a commenter named Tim Small posted the timings he had generated with a hacked version of cvt!
Based on his timings, I could get my monitor going stably at 2560×1440 at 50Hz. Enter the following in a terminal:
xrandr --newmode "2560x1440_50.00_rb" 200.25 2560 2608 2640 2720 1440 1443 1448 1474 +HSync -Vsync xrandr --addmode HDMI1 "2560x1440_50.00_rb"
When you enter after the second line, the monitor should switch to the 2560×1440 mode. After having done this, 2560×1440 appears as a selectable mode in the Ubuntu Displays app.