Arch Linux

Rena

Member

From: Ontario

Registered: 2015-05-08

Posts: 13

Website

X fails to detect monitor supported resolutions

I have 3 monitors connected to a Radeon HD 7750, using the radeon driver:

• Left: NEC MultiSync 90GX², 1280x1024, connected via DisplayPort-to-VGA adaptor

• Middle: Samsung SyncMaster BX2335, 1920x1080, connected via DVI

• Right: LG Flatron Wide, 1680x1050, connected via HDMI

On every reboot (warm or cold), X fails to detect the NEC monitor's supported resolutions. xrandr will only set it to 1024x768 or less, and it shows "no signal". However if I disconnect the VGA cable, plug it into another monitor (which is broken, but still powers on), and run xrandr again, it lists up to 1280x1024. If I then set the correct modes and layouts, then return the VGA cable to the NEC monitor, it works just fine. Turning the display off via xset doesn't cause any issue either. So on every reboot I have to move the cable to a spare monitor, set up xrandr, then move the cable back.

How can I save this working configuration and force X to apply it on boot even though the monitor for some reason claims to not support it?

I didn't have this issue with Ubuntu, but my setup was a bit different there, so possibly it just didn't manifest.

Here is the Xorg.0.log and journalctl -k from the most recent boot. The get-edid output is also interesting (and contains some control characters which pastebin removed).

WorMzy

Forum Moderator

From: Scotland

Registered: 2010-06-16

Posts: 11,894

Website

Re: X fails to detect monitor supported resolutions

Hi Rena, welcome to Arch. This topic doesn't really fit into the Multimedia and Games category, so I'm going to move it to Newbie Corner where it's more likely to get attention.

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Lone_Wolf

Forum Moderator

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 11,958

Re: X fails to detect monitor supported resolutions

according to the user manual, the NEC multisync 90GX2 has a DVI-D connector.
Maybe you could connect it directly and then get the correct edid ?

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Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

(A works at time B)  && (time C > time B ) ≠  (A works at time C)

Rena

Member

From: Ontario

Registered: 2015-05-08

Posts: 13

Website

Re: X fails to detect monitor supported resolutions

That's an interesting idea, but I'm not sure how it'd work. The GPU has only one DVI port and the middle monitor connects via DVI only (Samsung >.>). So if I used DVI for the NEC monitor, I'd have to get some sort of adapter for the Samsung...

Last edited by Rena (2015-05-13 18:08:14)

Lone_Wolf

Forum Moderator

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 11,958

Re: X fails to detect monitor supported resolutions

The NEC on DVI would be only temporarily to get it's real edid-data .
Once you got that in a file, you can use a special kernel parameter at boot to force use of  the real edid-data for the NEC monitor.

https://wiki.archlinux.org/index.php/Ke … s_and_EDID describes how it could be done.
Note that configuring this is tricky.

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Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

(A works at time B)  && (time C > time B ) ≠  (A works at time C)