external screen no longer support native resolution

[Barry Scott]

On Tue 21 Jul 2015 14:32:08 Frederic Muller wrote:
> Hi!
> 
> I just upgraded to F22 and my external monitor (a Koios 24" 1920x1200)
> no longer works in its native resolution. I can only get 1280 x 768 to
> display.
> 
> Everything was working well before. My video chip is the Intel HD
> Graphics 5500 (Broadwell GT2) (the laptop is a X1 Carbon 3rd generation).
> 
> GNOME display settings does offer the native resolution but it just
> doesn't work (I get an screen switched off).
> 
> How would you troubleshooting this?

Look in dmesg for errors. If you see problems with EDID it can
be a cable fault, try another cable.

Use xrandr --verbose to see what Xorg makes of the screen.
You should have EDID and the 1920x1080 mode should be listed.

Barry