Originally Posted by mpaganini
I've been running two X-servers on the same graphics adapter (same display, different virtual terminals: Alt-F7/F8) on Debian/Ubuntu for years.
Please note that this is a different topic: this thread is about running two
X-servesr concurrently where the first X-Server should use the first output
of a video card while the second X-Server should use the second output
of the video card. The two X-Server could be configured to take their
input from a separate set of mice and keyboards so that two people
could work at the same time using the same PC. This would be called
a "Multiseat" setup, but as of today this only works with "Xephyr", where
you start one "physical" X-Server with two screens and then run an
instance of Xephyr on top of each X-Screen. Unfortunately, 3D support
in Xephyr is experimental and performance is lagging behind the physical
X-Server. I guess XGL would also work (where 3D performance is acceptable),
but XGL is deprecate.
Now what you are asking for is running two X-Servers concurrently, but
only one of the two X-Servers "owns" (both outputs of) the video card at
a time and where you can switch between the two X-Server with
ALT+CTRL+F7/F8. Means, you can not see the output of both X-Servers
at the same time. To my knowledge, this feature has never been officially
supported by nvidia but worked flawlessly for many years - at least for me it
still works with 185.18.14 on a GTX260. Can you please post an
nvidia-bug-report.log? (I'd recommend to open a new thread) Maybe
your setup just needs some fine tuning.