I would like to quickly ask if someone is familiar.

This Kubuntu installation has been running fine in the sense of KDE. I attached the disk to a new motherboard and the issues seem to have started then.

There are two issues:

- When my monitor goes off (and it sometimes does, unfortunately) upon "restart" KDE won't give me back the image. It stays black with a mouse pointer.

I know xrandr still works because I have seen a background script of mine change the resolution of the monitor while this black screen was active. But no matter what I do (and my knowledge is limited) I cannot get it to give me back anything visible. I have not experimented yet too much with a 2nd monitor, but I think it did not help.

- Starting KDE takes longer than usual. Instead of the instant desktop you get first a black screen and it can take up to a minute before plasmashell (I think) properly loads.

Sometimes the desktop stays black. Other times it gets the wallpaper. But it might not get the panel. It takes very long and I don't know why.

This time can very between 10 seconds and up to a minute or longer. I have once seen "kcmserver" take 100% for a while. Other times there seems to be no activity.

Now:
* I am using the same graphics card
* It is stuck in a fewer-lane x16 slot in this new motherboard
* The motherboard is Abit AX78
* It is a dual lane (dual slot) motherboard (2x graphics card position available)
* There are no visible errors to my mind in Xorg.log
* I would like to know where to find more errors
* The GFX is a GT 640 that is supported on my kernel just fine, using Nouveau
* There seem to be no X issues, it seems to be purely KDE
* I have replaced my home directory with an older backup (actually not older than last new year's eve)
* There should be no errors in the user profiles
* A new user exhibits the same problem
* I have also seen it happen on the Kubuntu 16.04 Live DVD
* I am running Kubuntu 16.04 with Edgers PPA atm. I was running this before on the old motherboard as well. The old motherboard was Via chipset. I have also had a different AMD chipset (actually multiple) and never had a problem. I have had 780G motherboard, 785G motherboard, this is now 760, both SB700 or SB600 SATA controller, I have never had these problems before and the graphics card and drivers are the same, system is the same.
* There is one new alien (but unused) PCI card in the system which is a HighPoint raid controller taking up the first x16 slot.

I have no clue why something could be taking so long. I also don't know what suddenly creates these blackouts after the monitor turns off.

I would be most interested in KDE logs or troubleshooting, but...

I am currently reinstalling all packages in my system. So my logs may be muddled. I will provide a clean Xorg.log later if you want, but everything seems normal to me, glxinfo is normal, dmesg is pretty much normal apart from the usual hickups, the only thing interesting in journalctl at this point is:

jan 07 18:25:49 xenpc pulseaudio[2298]: [pulseaudio] module-x11-publish.c: PulseAudio information vanished from X11!
jan 07 18:25:49 xenpc org.kde.kglobalaccel[2158]: The X11 connection broke (error 1). Did the X11 server die?

I am not sure when that happened. I would need to create some clean logs when first starting KDE, for instance.

To add to this I only seem to be able to reproduce the issue when my only connected "monitor" is a HDMI TV. When the DVI-I monitor is also attached, the problem (of the blackout) seems to be not reproducable.

After attaching it and then turning it off (power disconnect) I can also not reproduce it as if the graphics card detects the connection even when off, or it remembers that it had been connected before (or KDE does).

So: HDMI-1: problem.
HDMI-1 + DVI-I-1: no problem.

This is for the blackout.

If running 16.04, ensure to install the backports ppa. QT 5.5 and earlier versions of plasma have many dual monitor issues. Newer versions of plasma (5.8.5) , while not perfect, are much more stable and predictable.

Indeed I am running 5.5. Thanks for the tip.

Maybe I did not get this issue earlier because the monitor was always at least attached. Very weird.

So not exactly dual monitor; however I did fix some of that with my own xrandr script.

However it seems like a good thing to try.

I am currently unpacking 2GB of packages to ensure there is no filesystem inconsistency between packages and installed files.

It takes a while lol. I hope it won't conflict with Edgers PPA, but I guess not.