[Nouveau] multiple cards and monitors with xrandr and opengl

[Sampsa Riikonen]

Dear Devs,

We have achieved a desktop of up to six monitors, with openGL running
succesfully on the desktop, with the following setup/features:

* Ubuntu 16+
* Xrandr
* Noveau driver
* Two gtx750 graphic cards

Each (identical) graphic card has 2xHDMI + 2xDVI connectors, which we
connect to the monitor array.

So far it works with six monitors, but we'd like to achieve eight. 
However, throwing in more monitors, results in monitors starting to drop
out (black screen).  However, xrandr sees them correctly.

The nv$dia proprietary driver is not an option - they have artificially
restricted the amount of monitors in the "base mosaic" feature (ref.
https://www.phoronix.com/forums/forum/linux-graphics-x-org-drivers/x-org-drm/46705-linux-multi-head-success-with-8-monitors-in-1-x-screen-without-xinerama
).

What might cause the monitors to drop out?  I can provide some logs
later next week (which file should I look at?)

Could using nv$dia's proprietary firmware in noveau help?

Regards,

Sampsa

P.S. This seems to be a bit outdated.. ?

https://nouveau.freedesktop.org/wiki/MultiMonitorDesktop/

.. it implies that xinerama must be used to combine screens from two
different graphics cards into a single screen which implies that opengl
should not work, right?