I have a laptop with a GeForce GT 650M. I recently installed Kubuntu 20.04 and have nvidia-prime installed.
I can select PRIME Profiles in nvidia-settings and I have "NVIDIA (Performance)", "NVIDIA On-Demand", and Intel (Power Saving Mode)".
When I select Intel, I suspect my NVIDIA card is still active because the laptop seems warmer than it should be and battery life is pretty bad.
In Kubuntu 18.04 I was able to use bbswitch to turn off the NVIDIA card. However, that doesn't work now. I get an error when I try modprobe.
$ sudo modprobe bbswitch modprobe: ERROR: could not insert 'bbswitch': No such device
And indeed, dmesg shows:
[12360.793484] bbswitch: version 0.8 [12360.793498] bbswitch: Found integrated VGA device 0000:00:02.0: \_SB_.PCI0.GFX0 [12360.793509] bbswitch: No discrete VGA device found
And from lspci:
$ lspci | grep VGA 00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)
It only shows the Intel card here.
So it looks like my GPU simply does not exist.
However, if I change the PRIME profile to any of the NVIDIA ones, lspci does show the NVIDIA GPU and glxinfo and friends show the NVIDIA card being used. So it does work!
So my question is, does Kubuntu 20.04 do something to drop the GPU from the PCI bus to power it down (and failing to power it down)?
Ultimately, I would like to power it down completely (there is no option in the BIOS). I have tried to go the bbswitch way, but if there are other ways, that would work too.