I have the same problem with the nvidia 1080 card.
i have ubuntu 16.04 with nvidia 375.20
Section “Device”
Identifier “nvidia”
Driver “nvidia”
BusID “PCI:1@0:0:0”
Option “ConstrainCursor” “off”
Option “RegistryDwords” “PowerMizerEnable=0x1; PerfLevelSrc=0x2222; PowerMizerLevel=0x3; PowerMizerDefault=0x3; PowerMizerDefaultAC=0x3”
Option “NoLogo” “1”
Option “Coolbits” “1”
EndSection
But it looks like it doesnt recognize the settings. Nothing works.
edit: downgrade to 367 everything works fine :)