[SOLVED] Radeon RX580. How to get equivalent of 'Xinerama' multi-monitor screen resolution as Geforce GTX 1050Ti

I upgraded from Geforce GTX 1050Ti to Radeon RX580. Basic reason was to get better performance from X-Plane 11 in Steam.

I also upgraded CPU from Ryzen 5 to Ryzen 7.

I then did a complete reinstall of Manjaro KDE.

I am happy with the performance of the Radeon RX580. However, one feature of the GTX 1050Ti that was enormously satisfying was the 'Xinerama' setting that allowed me to combine my three monitors into one large monitor. It took much research to get Xinerama to work. There seems to be very scanty/confusing documentation about getting Xinerama to work.

What did work was changing this line in the '90-mhwd.conf' file (if I remember the name of the file correctly):
Option "Xinerama" "0"
to
Option "Xinerama" "1"

I then would restart 'sddm' with this command:
$ sudo systemctl restart sddm

After this restart, my 3 monitors acted as one large monitor.

Flying X-Plane 11 in Steam was marvelous with 3 monitors. But the graphic performance was sub-optimal even with the GPU and CPU overclocked.

I want to be able to achieve the same result with the RX580 of combining all three monitors into one large monitor.

I have searched for days, but have found no clear, or even closely-related answer.

Any ideas?

Thanks!

I had KDE spanning two monitors from a radeon R3 without screwing with any configurations. I just used the KDE display options. Try pressing meta+P to bring up the paging widget. You should be able to get it into spanning mode from that. If the monitors are the wrong way round, you'll need to set which is primary and re-arrange them using system settings>displays.

Thanks for the suggestion.

However, I am not able to find any setting using Meta-P that creates one large monitor from three monitors.

Each monitor has a display resolution of 1920x1080.

Using Xinerama with my Geforce GTX 1050Ti , I was able to create one combined monitor with a resolution of 5,760x1080 (1,920 x 3 = 5,760).

Pressing Meta-P shows these options:
1 - Switch to external screen
2 - Switch to laptop screen
3 - Unify outputs
4 - Extend to left
5 - Extend to right
6 - Leave unchanged

Selecting options 3, 4 or 5 still only gives a maximum resolution of 1920x1080 for each of those three options.

I cannot find any way to get a resolution of 5,760x1080.

Still looking for ideas :slight_smile:

Thanks for the suggestion!

Did you try the System Settings I also mentioned? You can drag and drop displays in that dialogue. I reckon you will be hacking xorg configurations again though, but it might be worth asking on the AMD and KDE forums too if you haven't already.

Yes, I did. Sorry I didn't mention that sooner.

I can only get a maximum resolution of 1920x1080 for each monitor individually using System Settings.

As with using Meta-P, Displays--System Settings Module offers a 'Unify Outputs' option, which I would have assumed does what I want. But I have never seen any change in my monitor output when I click on it.

I have been using KDE for probably 13 or more years, on different distros, and have always just used 'Displays--System Settings Module' to set my display options. I have only had good graphics cards and multi-monitor setups for the past 2 or 3 years, so it has never been a big issue before.

Thanks again for your suggestions!

I'm using a Geforce GTX 960 at the moment, otherwise I'd have a play around with it too as I could potentially hook up 3 panels, 2x 1024x1280 via DVI and a 2560x1440 panel I use for gaming on my other system via HDMI if I could find the long cord in the tangled up mess someone left them in :unamused: (The joys of parenthood, my Son won't get away with it and will be sorting it out. Any breakage he will have to pay for)

The AMD equivalent of Xinerama is called Eyefinity but I don't know if that feature is in the amdgpu driver or not.

Probably an xyproblem.
It might help (you) if you explain why you want this resolution, since it sounds technically a special case. What do you need it for? How do you use this in your workflow?

this :slight_smile:

This is the special use. I would normally expect this "monitors combined to one" be taken care by the application (Steam) though.

Because it's an old method. But don't you have your old Xorg conf file that was used in the old setup? Then you would only need to adjust the new gpu settings.
And have you started from Archwiki? There is a very clear example with great comments.
Anyway post info and read the Xinerama article.

inxi -SMGxxxaz
xrandr
mhwd -li
for Xconf in $(ls /etc/X11/xorg.conf.d/*.conf); do echo -e "\n" $Xconf ; cat $Xconf ; done
for Xlog in $(ls /var/log/Xorg.?.log); do echo -e "\n" $Xlog ; cat $Xlog ; done

BTW, setting a unified monitor seems it should make your DM screen be spread into three monitors. Or how was it in your previous setup?

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As far as I can find out, this is true for Steam under Windows, but not for Steam under Linux.

Multi-monitor support (getting 5,760x1080 resolution) is a feature built into Windows, at least with the GTX 1050Ti. I did a short dual-boot with Windows, and multi-monitor support 'just works'.

X-Plane 11 (in Steam) has a feature designed for using 3 monitors. You can toggle a setting where the left monitor simulates the view from the left window of the plane, and the right monitor simulates the view from the right window of the plane. BUT, that feature only works in Windows.

When I finally uncovered how to use Xinerama in Manjaro, I could achieve the same result of stretching X-Plane 11 (and XRebirth, etc) across all 3 monitors without the complexity and frustration of installing Windows on this machine.

I have to solve Windows problems in my day job and my own IT business. I will only run Windows in VMware on my own computers. I just don't have the time or patience anymore to deal with Windows headaches :slight_smile:

Since I got this solved with the GTX 1050Ti, I hold out hope for a solution with the RX580.

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you could try playing the game in windowed mode & just resize it to cover all monitors

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Thank You!

I had tried to find how to enable windowed mode is Steam last night by looking through Steam's settings, but I couldn't find the option. I am NOT a gamer. I basically play only one game: X-Plane 11 :slight_smile:

Your comment led me to search the Steam forums this morning, and I finally found some forum posts that explain where the Windowed Mode setting is accessible inside X-Plane 11.

Works now!

Thank you. Such a simple solution after all!

Hopefully this thread helps someone in the future.

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no worries. steam basically only installs & keeps your games updated for you, any options will usually have to be changed in the games themselves

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