I didn't know about the SLI breakage, my bad. Just did a clean install and I can confirm that it's working as it should:
$ xrandr --listproviders Providers: number : 2 Provider 0: id: 0x65 cap: 0x9, Source Output, Sink Offload crtcs: 3 outputs: 3 associated providers: 1 name:modesetting Provider 1: id: 0x3f cap: 0x4, Source Offload crtcs: 0 outputs: 0 associated providers: 1 name:nouveau # cat /sys/kernel/debug/vgaswitcheroo/switch 0:IGD:+:Pwr:0000:00:02.0 1:DIS: :Off:0000:01:00.0 -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to nvidia-prime in Ubuntu. https://bugs.launchpad.net/bugs/1765363 Title: prime-select intel is not powering off the nvidia card Status in nvidia-prime package in Ubuntu: Confirmed Bug description: Right now, it seems that prime-select intel makes sure the nvidia driver is not loaded, as nvidia-settings reports. But my power consumption is > 20W. cat /proc/acpi/bbswitch reports the card is still on. If bbswitch and powertop are reliable, then the nvidia card is still powered. This is a thinkpad w520 in Optimus mode. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: nvidia-prime 0.8.7 ProcVersionSignature: Ubuntu 4.15.0-15.16-generic 4.15.15 Uname: Linux 4.15.0-15-generic x86_64 ApportVersion: 2.20.9-0ubuntu5 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Thu Apr 19 19:56:21 2018 Dependencies: EcryptfsInUse: Yes InstallationDate: Installed on 2017-12-14 (125 days ago) InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20171018) PackageArchitecture: all SourcePackage: nvidia-prime UpgradeStatus: Upgraded to bionic on 2018-03-09 (41 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/nvidia-prime/+bug/1765363/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp

