I’m trying to make a setup with in total 7 monitors (one monitor gets mirrored with the sixth monitor) run on my machine with Ubuntu 20.04 on it. I am using two GTX980TI (Windforce) with an SLI cable and already tied a few different scenarios (all configured by nvidia-xconfig). Its using standard X11 with GDM on it.
Since this is a dual boot, the same hardware setup is running without any problems on Windows 10 with SLI activated in 6 and 7 monitor mode (seventh monitor is not always connected).
From hardware perspective, both cards having all three displayport in use. The second card powering the upper row of monitors powering the seventh monitor (attached by HDMI) that will get mirrored with one of the displayport connected monitors.
Card 0 - main: -> DP0, DP1, DP2 Card 1 - secondary: -> DP0, DP1, DP2, HDMI0
So far, I tried some different possibilities, starting with a second screen configuration next to the main screen configuration, which does not really work great on GDM at all. But at least all screens get initialized with an unused X screen session.
Otherwise I tried using Xinerama, with came out as disaster with everything I tied. It was not working at all and always ended in an black screen with mouse pointer on it.
With use of Base Mosaic (tried with driver 470, 495, 460, 450, 390) I was finally able to use more than 3 monitors with one X screen, but it was only able to let me activate 5 monitors with the error:
• MetaMode 1 of Screen 0 has more than 5 active display devices.
I did not tried this with the seventh monitor attached, but the sixth monitor will already automatically be turned off at this point.
As extra from all that I also tried when downgrading the driver to use legacy SLI/MultiGPU modes as described in docs, but that came out to only work with one monitor at all and not really well.
Since I already wasted a lot of time with this topic, I wonder if there is some limitation that wont let me pass on this.
Is there some way to make it work with Base Mosaic on this specific hardware?