I am running a Lenovo W541 with 4.9.4-1-default. I have done very little with
this system. This happens from a normal install. If I unplug the power cord
everything will freeze. I can not switch to a tty. CTRL-ALT-Backspace will not
work. Everything locks up.

I can boot on battery and I get to the login screen. At the login screen I can
switch ttys. As soon as I log into anything even Ice WM the system locks up. I
can't switch to a TTY, can't restart X, nothing works. If I boot with acpi=off
my keyboard and mouse do not work, so I can not test if that fixes it.

Let me know what logs I should post. I'll edit this if I find anything if
interest. 

lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation 4th Gen Core Processor
Integrated Graphics Controller (rev 06)
01:00.0 VGA compatible controller: NVIDIA Corporation GK107GLM [Quadro K1100M]
(rev a1)