To start another X-session, you can modify the file /etc/X11/xdm/Xservers
put this line
:1 local /usr/X11R6/bin/X :1
below
:0 local /usr/X11R6/bin/X :0


then in the file /etc/X11/xdm/xdm-config, make a copy of the settings for display 0 for display 1
DisplayManager._1.authorize: true
DisplayManager._1.setup: /etc/x11/xdm/Xsetup_0
DisplayManager._1.startup: /etc/x11/xdm/GiveConsole
DisplayManager._1.reset: /etc/x11/xdm/TakeConsole

instead of
#startx
use
#startx --:1
to start the X-session


:P