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SD: external screen broken for anyone else or just me?
damarrin 29 Aug
A while ago I was playing the SD on my TV and everything was fine. Res was limited to 1280x720 (as per the setting Valve introduced a while back) and as long as I remembered to switch refresh from 40 to 60 I had no problems with anything.

I just got the JSAUX dock so naturally I wanted to try that again and I’m getting a serious headache from it all.

I tried stable, beta and preview, it’s the same on all of them.

In gamemode, as soon as I connect the hdmi cable, image on the internal screen disappears and nothing appears on the TV. That’s it, I haven’t got any further than that.

It’s a little better in desktop mode. The selection box that appears works and I can turn on the external screen, but the resolutions come up all messed up. The internal screen switches to 600x800 (vertical on the screen) and I have to configure everything manually so it becomes useable.

I once disabled the internal screen in desktop mode and the next time I connected the dock I got no image on either screen and had to delete .local/share/kscreen to get back to a useable config.

In other words, it’s all a huge mess. Plus, the setting in gamemode options to limit resolution on external screens seems to have disappeared. Anyone can try if an external screen works for you? Thanks.
This topic has an answer marked - jump to answer.
NoiramSang 30 Aug
My personal experience is the following.

I have a Steam Deck, I use the USB 3.0 dock from JSAUX, and I most commonly (not exclusively) use an HDMI-to-USB adapter to have it be seen as a webcam, to use my Chromebook as a second monitor.

I use an external display (using HDMI) in three ways: Gaming Mode, Desktop Mode, and SUSE.

1. Gaming Mode hates two monitors enabled at once. It will display only on the external monitor, with the Steam Deck screen going black. From what I have read, this is the expected behavior. Removing the HDMI cord results in the Steam Deck's screen displaying again.

2. In Desktop mode, it works as expected. Video and audio reach the second screen, and it can be adjusted in all the ways you would expect: resolution, orientation, etc.

3. In SUSE, which I boot from an external SSD using USB, I learned to never boot with an external monitor connected. It only displays on the external monitor, and will not go back until restart (log off?). This can also happen if I hibernate the computer. Other than that, it is basically the same in SUSE as in SteamOS Desktop Mode.

I have not done extensive testing, but that is my current experience without making any notable changes to settings, files, etc.

Last edited by NoiramSang on 30 August 2022 at 3:17 am UTC
damarrin 31 Aug
Thanks for the answer, it looks like my config must have got messed up somehow, maybe a write to Valve support is in order.
damarrin 7 Sep
I fixed it (sort of).

Before, the SD would display at a low resolution on the TV (1280x720 iirc, there was a setting there which is now gone) and it worked fine. Now, it insists on 4K with no apparent way to change the resolution and that was too much for it/the HDMI cable/the TV.

I had to limit HDMI bandwidth in the TV's settings (switch from Mode 2 to Mode 1 for the HDMI input) and now the image displays correctly.
wojtek88 8 Sep
Welcome back, it's been a while since I wrote something here. In 2018 I've received Switch from my wife and I've abandoned Linux gaming, but now, for 4 months already I am back, as Steam Deck arrived to my home :)

I don't know @damarrin if it matters to you, but I use on daily basis LG UltraFine 27UN880-B Ergo 4K HDR for work, and I connect my Steam Deck to it via usb-c without an issue.

In gaming mode performance of the UI is bad and games do not see other available resolution than the one from SD, however in desktop mode everything works fine, I've been playing some Pillars of Eternity 2 and Sekiro this way.
damarrin 8 Sep
Yeah, gaming mode UI is pretty bad in 4K.

As for game res, you can set it in the game's options in Steam (cog on the right).
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