I have seen in forums and manuals that you have to add
Option "Coolbits" "value"
to xorg.conf or similar files.
I have been able to get this working for the first GPU, the one rendering the display. I have not been able to get overclocking options in nvidia-settings for the second GPU, not rendering any display.
I have tried things like
Section "Device" Identifier "Videocard0" Driver "nvidia" BusID "PCI:2:00:0" Option "Coolbits" "12" EndSection Section "Device" Identifier "Videocard1" Driver "nvidia" BusID "PCI:3:00:0" Option "Coolbits" "12" EndSection
in the various files: xorg.conf, 99-nvidia.conf, nvidia-xorg.conf. Everything I have tried has led to black screens, no overclocking capability or overclocking capability on the first GPU only.
Is it possible to unlock overclocking for both GPUs, if so how?
I have not found this question asked anywhere. I am running 346.59 drivers on Fedora 21.