Quadro NVS 450 on Linux

Hello gentlemen,

I have used Quadro NVS 450 (two gpu, 4 displayport) in a triple-monitor set-up for a while but had to upgrade to Ubuntu 15.04 Vivid x64 because security updates ceasing next month.

What is the recommended configuration/Window system/display manager/desktop environment to get as much acceleration as possible on Linux with 2-GPU, 3-display?

I had been limping along with xorg.conf composite 1, Xinerama 1 then using a monitor layout from nvidia-settings which worked with about 80% acceleration features for KDE lightdm X.

Unfortunetaly, the upgrade was the end of graphics acceleration. I am back to Metacity of five years ago with absolutely no acceleration, everything else goes back to greeter screen. I think gnome has tried to not support this metacity for years.

I upgraded to 340.76 of 150127 but it still crashes.
The new windowing system wayland does not support nVidia binary drivers.
The nouveau driver’s developers claims it to work for this card, but it doesn’t and never did.
so only X.
sddm and lightdm at least start, gdm is black screen.

Desktop environments:
So the good news is that Metacity works but windows are dragging their feet: redraw takes seconds.
KDE gets to about 90% then everything goes black but you can start unframed windows using Alt-F2. Ctrl-Alt-Del logs out.
GNOME (shell) displays a black screen for a while, the goes back to login.
Ubuntu (Mir) works kind of but suddenly all windows have black content panes.
Compiz doesn’t work but they intentionally do not support multi-GPU.
failsafe doesn’t work at all :)

The funny thing is that there is no real log output. KDE in fact does provide a cryptic stack trace, different apps each time, the others just start shutdown without providing a reason.
here’s an example: https://bugs.kde.org/show_bug.cgi?id=349409

Helpy help?

This problem appears to be caused by QT http://www.qt.io/ package qt5-default at present not working for environments without randr prior to version 5.5. https://bugs.kde.org/show_bug.cgi?id=343844

QT 5.5 was released as a beta on 5/15/2015 http://blog.qt.io/blog/2015/05/15/qt-5-5-beta-released/

It is unsure how nVidia will support Quadro NVS 450 in a Linux world moving to Wayland. In 2009, this was the only fan-less triple digital display solution. For a single card slot with DisplayPort price didn’t matter. However, only the nVidia binary driver supports this twin-G98-gpu card. Only nVidia can keep it working.