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#1 2018-06-07 15:52:21

sicklybeans
Member
Registered: 2018-03-14
Posts: 1

Can I use a single Xorg Screen with different graphics cards?

I have a laptop with an onboard Intel GPU and a discrete NVidia GPU. I often work with an external monitor connected.

Problem

The laptop is designed to use the intel card for outputing to the display. However, on linux it is currently only possible to display to an external monitor using the nvidia card. This means that to use my laptop with an external monitor, I have to use the nvidia card.

What I would like to happen

Run Xorg with a single "Screen". That "Screen" uses the Intel card for outputing to the native laptop display. It uses the Nvidia card for outputing to the external monitor.

What does happen

By playing with xorg configs, I've been able to do any of the following:
1. Run a single Xorg screen with the Nvidia card - this allows me to use both monitors. But it has drawbacks (below)
2. Run a single Xorg screen with the intel gpu - in which case nothing shows up on the external monitor because of the above mentioned issue.
3. Run two different Xorg Screen's on each display with different graphics cards. This is not ideal since it acts almost as if I were running two different OSes.

Drawbacks

The 1st solution is my default. But it has problems:
1. The intel GPU is essentially being wasted since it's not used
2. Increased power consumption by using the Nvidia graphics card all the time.
3. Some of the Nvidia graphics card's power is wasted in outputing to the display (which is really supposed to be done by the intel card). If I had to guess, I would say that this leads to decreased performance while gaming.
4. Random problems like xbacklight not working since it's not compatible with the Nvidia drivers
5. Even when I unplug the external monitor, I still am powering my native display with the Nvidia card


Does anyone have any recommendations about how I would go about solving this?

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#2 2018-06-07 21:05:58

teckk
Member
Registered: 2013-02-21
Posts: 278

Re: Can I use a single Xorg Screen with different graphics cards?

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#3 2018-06-11 07:32:51

Askannz
Member
Registered: 2016-10-22
Posts: 20

Re: Can I use a single Xorg Screen with different graphics cards?

I am on the same boat (optimus laptop, model is MSI GE63VR 7RE) I can use the HDMI output only when I run Xorg on the NVidia card.

I suspect the problem is that the HDMI port is hardwired to the NVidia card, while the built-in screen is hardwired to the integrated Intel GPU. When running Xorg on Intel, the integrated GPU cannot access the HDMI output because the NVidia card does not allow it. On the contrary, when running Xorg on NVidia, the NVidia GPU can access the built-in screen thanks to the PRIME technology (which is why the built-in screen appears as a PRIME display in nvidia-settings).

The wiki suggests a solution, here : https://wiki.archlinux.org/index.php/PR … erse_PRIME
but that seems to work only with the open-source driver "nouveau". For the proprietary driver there is a link to Nvidia page but I think the author of this wiki page has it confused : the linked page refers to accessing Intel display from NVidia, not the opposite.

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#4 2018-06-11 08:27:10

ngoonee
Forum Fellow
From: Between Thailand and Singapore
Registered: 2009-03-17
Posts: 7,122

Re: Can I use a single Xorg Screen with different graphics cards?

Search for intel-virtual-output, this will allow you to access the HDMI port monitor and reflect that to the intel card.


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