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James Li avatar Ubuntu

PC no longer identifying 3 other monitors. Thoughts?

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James Li

Ubuntu 20.04, Sceptre 24" monitors (2) (they have HDMI inputs), ViewSonic VG2439m-LED 24" monitors (2) (they have display port monitors), HDMI to mini DP cables (2), DP and mini DP cables (2), and Nvidia NVS 510 graphics card (mini DP outputs, worked with all 4 monitors before).

A bit of context: A few days ago, I connected the 4 above monitors to my graphics card. For about a week, it ran fine.

Today, I noticed that only my main monitor (connected to output 1 of the graphics card) turned on. The other monitors, which were all plugged it, didn't even respond (i.e. they didn't even get a "no signal" error, which they used to when there was an error).

I started by restarting my PC, unplugging the cables between the monitor and the graphics card, and turning it back on. However, the issue remained.

I should also note that previously the other 3 monitors will light up when the PC turns on, however they didn't anymore.

I tried plugging in the cable that ran from output 1 (and connected to the good monitor previously) and plugged it into other graphics outputs, which didn't work either.

At no point did the machine detect the three other monitors.

I also tried swapping out the cables for other cables I had, but this didn't work.

However, when I switched out the SSD with an SSD that had Windows flashed to it, all four monitors just worked fine as soon as I started it up. I switched the Ubuntu SSD back in and it still had the same problem.

Any advice?

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Brian

Something changed in the Ubuntu OS or the BIOS setup. A driver update, multi-monitor was turned off in the BIOS setup, an upgrade messed with a config file, new driver version defaults to single monitor configuration, proprietary nVidia driver kick out by nouveau open-source nVidia driver.

Try nvidia-settings, Look at the monitors (or screens) section. Try reinstalling the correct nVidia driver apt install nvidia-driver nvidia-kernel-dkms --reinstall.

Follow the onscreen instructions. If that doesn't work, I'll eat my shorts!

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James Li avatar
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James Li
Haha I was watching the Simpson's when I read this! I'll give it a shot and let you know if I have any trouble
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Nate T avatar
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Nate T
Yup! That is exactly what I was going to suggest. I struggled running a 4 monitor setup with a nvidia gpu for months, and then I found out about the `nvidia-settings` package and it was fixed in 5 minutes. @JamesLi you may be able to get them back temporarily with `xrandr --auto` but as soon as the machine coes to sleep, reboots, or the display server is otherwise reloaded, you have a 50/50 chance that the configuration will be lost. That is why the settings app is needed
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Nate T avatar
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Nate T
Additionally, if it does not work and you are using the noueve driver, switch to the newest proprietary driver. At the moment, the newest is available with `sudo apt install xserver-xorg-video-nvidia-470`. Then use `modprobe` to switch. Not sure if it works with noueve drivers. I am thinking I had to switch to get it to work.
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James Li avatar
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James Li
Worked great, thanks!
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