Sometimes the screen shows color banding. Nvidia-settings shows 24 bit color depth but the screen has banding instead of smooth gradients, on the desktop as well as in applications.
Killing Xserver with CTRL-ALT-BACKSPACE will bring the screen to normal (no more banding).
Killing Xserver again and the problem can come back randomly. Most of the times it’s fine but let’s say 1 times out of 50 it will have the color banding behavior.
Seeing this with driver 390.12 (not seeing with 346.35 which is the former driver that was used on this machine).
Not sures what causes it and if it is possible to prevent from happening ?
This kind of thing can happen if the cable or monitor is flaky. Can you please run nvidia-bug-report.sh in both the good and bad cases and attach them to your post?
I don’t know why 390.12 would be more sensitive to link training flakiness than 346 would be.
Some troubleshooting done:
On another machine, the problem is not randomly there but always present with 390.12 (384.98 also acts the same.) As soon as I downgrade to 346.35 the color banding is gone.
This machine is using an Avenview DisplayPort extender cable (model FO-DP-25-MM) and that seems to be part of the problem. (issue with the extender and some versions of the driver (384.98 and 390.12 are the 2 I tested that showed the problem)
To sum it up:
346.35 + Avenview Extender = No problems
390.12 + Avenview Extender = Color Banding (also seeing with 384.98)
390.12 + regular displayport cable = No problems
I’ll bring this up to Avenview for their consideration as well.
I’ll look into attaching the logs.
Thanks!
This system doesn’t have the Intel iGPU available as an option in the BIOS, and disabling the NVIDIA driver will simply switch to LLVMpipe software rendering. lscpi verifies that an Intel iGPU isn’t available:
I have noticed, however, that using the NVIDIA X Server Settings control panel, and switching dithering to Disabled, and then back to Enabled fixes things, but the process has to be repeated each time you reboot.