Nvidia has revealed that it had to remove a feature from its Linux driver in order to make it match the Windows feature. A Linux user with way too many monitors has complained on the official Nvidia forums about the lack of proper multi-monitor support in the latest drivers.
I’m using Ubuntu 12.04 with 3 monitors hooked up to it using BaseMosaic. This worked fine. I was on NVIDIA drivers 310 using two GTX 560Ti graphics cards with a SLI connector.
A few days ago I tried hooking up a 4th monitor, configured the xorg.conf file, but still only 3 monitors popped up. Then I tried installing the v325 drivers after uninstalling all the ubuntu nvidia packages. This only worked for 2 monitors, because I couldn’t get BaseMosaic working anymore, even not from the NVIDIA GUI after enabling advanced options.After a little bit of research I found that v310 only supports up to 3 monitors in BaseMosaic, the same is valid for v325.
In v295, however, it is possible to use 4 monitors using BaseMosaic. Why did the BaseMosaic supoort get limited to only 3 monitors? Currently I downgraded my drivers to v295 to be able to use 4 monitor without enabling Xinerama (I like the 3d support).
Will it be able in future drivers to support more then 3 monitors again using BaseMosaic?
Another user, apparently working for Nvidia, gave a very troubling answer:
For feature parity between Windows and Linux we set BaseMosaic to 3 screens
This means that the company chose to remove a feature from the Linux version of the driver that was not available on Windows, instead of doing the other way around.
It remains to be seen if Nvidia will make some modifications in this particular direction with its next versions.