Issue with 2x980TI and 6 monitors

I have just added a second 980TI to a system. I have 6 monitors connected to the 2 cards. Primary GPU has 2x Dell U2412Ms connected. All 3 are connected via Display Port on the cards to DVI-I on the monitors. On the second card I have 2 ViewSonics VX2349Ws connected the same way and an NEC LCD2070WNX that is connected via DVI-I.

Now for the fun: no matter how I attempt to configure the system, I can not get it to span all 6 monitors. Base Mosiac works with 3 (the original configuration that I had setup) but Base Mosiac only supports a MAX of 3. I am looking to have all 6 on the same x server with the ability to full screen an application on any single monitor.

I have constructed multiple xorgs including 1 that has 6 defined monitors and devices with Xinerama enabled but X will either come up incorrectlyl or Cinnamon will not start.

Resolutions on the monitors
Dells- 1920x1200 (bottom in line)
Viewsonics & NEC 1680x1050 (top in line).

Looking for any hint to start with.

Matthew

See this:
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

Only applies to Quadros, sorry.

Don’t know if a PRIME output setup would work. Either one 980 with nvidia driver + intel iGPU or both 980 with nouveau driver.