17.10 not detecting correct monitor refresh rate at 2560x1440

Asked by Txn on 2017-12-02

When using Ubuntu 17.10 (GNOME) with my Dell U2715H monitor, it does not detect the monitor's native refresh rate of 60Hz when set to its native resolution. GPU is an AMD Radeon RX480.

At its native resolution of 2560x1440, the only refresh rates that are available to choose from are 59.95Hz and 59.96Hz, both of which will cause the monitor to display an error message reading "The current input timing is not supported by the monitor display. Please change your input timing to 2560x1440, 60Hz".

The only way to make it work with 17.10 is to attach another different monitor to the system and set the U2715H's resolution to a lower one (e.g. 1920x1080), where 60Hz is correctly detected as the monitor's native refresh rate.

Oddly enough, this problem does not occur whilst using the live ISO image and can only be reproduced where 17.10 is installed to disk.

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Ubuntu Edit question
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Last query:
2017-12-05
Last reply:

Sounds like an EDID issue and the screen not reporting its abilities properly. I'm not sure how to work around it myself. You could try and make an xorg.conf file but I'm not sure if this is honoured by the new display server in Ubuntu.

Do other people have the same issue in forums online? Have you contacted Dell for support?

Txn (yearofthelinuxdesk) said : #2

I've not been able to find anything for this model in particular, but I have observed that people have reported this issue for other models. Regardless, I was not able to find any working solutions that were applicable to Wayland. Worth mentioning is that KDE Neon, which is using Xorg, seems to play along just fine.

I'll try and contact Dell for comment but I don't anticipate that this is something within their control.

Txn (yearofthelinuxdesk) said : #3

Not heard back from Dell on this yet but that aside, who should I be filing a bug report with?

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