I have Ubuntu 12.04 installed on my Lenovo ThinkPad T420S.
In BIOS I have an option to select graphical card: integrated intel card or NVS 4200M (or NVIDIA Optimus which is out of scope now).
When I select integrated intel card in BIOS everything works fine. When I select nvidia system freezes after grub screen. Sometimes I get weird "ATA revalidation failed". Magic button (Alt+Fn+SysRQ+E/I/S/U/B) doesn't work.
What I have tried:
- Installing recent nvidia-current from x-swat ppa.
- Purging nvidia-current and nvidia-common
- Updating T420s BIOS version.
- Updating kernel to 3.4.7.
- Booting old kernel 3.2.0-18.
I don't think this is hardware issue since Windows works fine.