[Bug 3240] bbswitch-kmod

[RPM Fusion Bugzilla]

https://bugzilla.rpmfusion.org/show_bug.cgi?id=3240

Simone Caronni <negativo17 at gmail.com> changed:

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                 CC|                            |negativo17 at gmail.com

--- Comment #7 from Simone Caronni <negativo17 at gmail.com> 2014-05-19 15:44:30 CEST ---
Hello,

bbswitch does not save any power if you are using an Optimus enabled laptop
with the Nvidia driver.

I have an Optimus laptop that I use everyday at work. I've written a guide for
Fedora 19 to use and configure the dual card setup:

http://negativo17.org/complex-setup-with-nvidia-optimus-nouveau-prime-on-fedora-19-2/

The guide is pretty much the same for Fedora 20, only the config file for
offload rendering in Nvidia is slightly different.

The bbswitch module is needed only if:

- Optimus is enabled in your bios
- The system has loaded the Nvidia drivers (it disables vga_switcheroo)

But unfortunately, to use it, you have to shutdown X, move Nvidia libraries out
of the way, delete the X.org config file, echo the bbswitch proc file and
restart X. This is what the customized Nvidia settings panel in Ubuntu does.

Another negative effect, is that with Nvidia and Intel, none of the card is
powered down and output displays management with xrandr is all messed up. If
you power off the Nvidia chip, there is no way to use the additional outputs
without restarting X.

If you are using the out-of the box experience of Fedora/RHEL, vga_switcheroo
is enabled (Nouveau drivers) and if there is no output connected to the Nvidia
chip, it is shutdown automatically. Even running a simple "xrandr -q" powers up
and down the discrete chip. Also monitor layout is consistent and adjustable
with any xrandr tool.

Basically with Nouveau/Prime, the Nvidia chip is always off unless you call it
explicitly with the DRI_PRIME=1 variable or connect an output of the card.

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