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what causes switch to discrete GPU with nouveau + optimus?

asked 2015-11-21 15:49:31 -0500

allencmcbride gravatar image

I just switched to Fedora 23 from Ubuntu. On Ubuntu, I was using an NVIDIA driver, but I gather that on Fedora it's safer to stick with nouveau. But I'd like to understand it better. Before, to switch between integrated and discrete graphics, I'd use nvidia-settings. But how does it work with nouveau? I've read that nouveau, unlike nvidia's drivers, supports Optimus, and I do seem to have Optimus. So I guess it's switching automatically? But based on what? Or do I need to control switching manually (perhaps by learning about DRI and xrandr)?

Dell 7737, 17"
NVIDIA GeForce GT 750M
Fedora 23

possibly helpful output:

# cat /sys/kernel/debug/vgaswitcharoo/switch
0:IGD:+:Pwr:0000:00:02.0
1:DIS: :DynOff:0000:04:00.0

% inxi -Gxx
Graphics:  Card-1: Intel Haswell-ULT Integrated Graphics Controller bus-ID: 00:02.0 chip-ID: 8086:0a16
           Card-2: NVIDIA GK107M [GeForce GT 750M] bus-ID: 04:00.0 chip-ID: 10de:0fe4
           Display Server: Fedora X.org 118 drivers: nouveau,intel (unloaded: fbdev,vesa)
           Resolution: 1920x1080@60.01hz
           GLX Renderer: Mesa DRI Intel Haswell Mobile
           GLX Version: 3.0 Mesa 11.0.4 (git-ec14e6f) Direct Rendering: Yes
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answered 2015-11-22 15:07:59 -0500

HoboPrimate gravatar image

I don't believe it's automatically switching, and Optimus does work with nvidia drivers. I also have dual graphics, and followed these instructions to install bumblebee, which gives Optimus support in Fedora. Afterwards, to run an application with nvidia graphics, do:

optimus application
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Thanks! I've read a bit about bumblebee, although I've heard mixed things about its stability. I may give it a try, although for now I'm mostly interested in learning about switching with nouveau. Thanks for letting me know that it doesn't switch automatically to your knowledge.

allencmcbride gravatar imageallencmcbride ( 2015-11-23 13:15:52 -0500 )edit

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Asked: 2015-11-21 15:49:31 -0500

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Last updated: Nov 22 '15