Lenovo ThinkPad T520
Installation worked without further setting adjustments.
The BIOS option Display->Graphics Device can be switched to these settings:
Use this with the xf86-video-intel driver. The nvidia card will be turned off, which means that the system will consume less power and you will not have to worry about installing the nvidia drivers.
The integrated graphics is fast enough to run some older games. It is a good option if you do not use demanding 3D applications
A major disadvantage of this mode is that the DisplayPort will not work, because it is hardwired to the Nvidia card.
This will give you good consistent 3D performance in all applications, without having to worry about the complexities of bumblebee. It is also a good option if you want an easy way to connect and use a DisplayPort monitor.
You will not get the power-savings of running from the intel-gfx and turning the discrete nvidia card off. Another disadvantage is that you cannot use this mode to run tripple-head with 2 external Monitors on VGA and DP. This is a hardware limitation, the discrete-nvidia and integrated-intel card can both only drive at most 2 different screens each.
If you choose this option, set "OS Detection for NVIDIA Optimus" BIOS Option to Disabled.
See the Bumblebee page for details on how to use both cards with linux.
Screen freezes before login prompt when using discrete graphics
I had this problem when using the BIOS-Option Discrete Graphics together with nvidia driver. The nouveau driver got autoloaded on system boot and prevented the proprietary nvidia kernel module from being loaded. When i removed the nouveau Driver, the system got confused with the graphics-mode setting on startup. To solve this follow these instructions:
GRUB2#Disable_framebuffer (if you are using GRUB2)