For some strange reason my box’s Xorg stopped working after a clean install and installation of the handy NVidia packages from Livna. The box would boot but when it was time to enable X it just flickered 10-20 times and a console login appeared. With some luck the problem was easy to fix, I just needed to add a line to /etc/X11/xorg.conf under the “Device” section:
BusIDÂ “PCI:1:0:0”
While at it I decided to check if I remembered correctly that NVidia had added SLI support to it’s Linux drivers. It turns out it did and it works great 
If you want to enable SLI the NVidia Display Settings application will be useless. You need to run:
/usr/sbin/nvidia-xconfig –sli=on
Or, if you are planning on editing xorg.conf then just add this line under the “Screen” section:
Option        “SLI” “on”
After a Xorg restart the NVidia Display Settings should display the 2 GPUs under the “X Screen 0” (before it would should just 1 althouth it would display thermal data for all GPUs). It looks like it also adds a “Enable SLI HUD” under the OpenGL Settings but I couldn’t really see the effect yet 😛
PS: Looks like this boot problem is a NVidia Driver problem without ETA to be solved (info from NVidia forums).
