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Is there a way to select a primary graphics other than onboard graphics? I have two different dedicated graphics cards in my machine, one GT640 and a GTX970. I am trying to set up the machine to set up Linux Mint to use the GT640 and later I will enable GPU passthrough to a KVM Windows VM for the GTX970. However currently I can only get the system to boot on the GTX970 not the other graphics card, and the graphics drivers are not working with the other graphics card anyway.

Things I have tried:

  • Installing Mint then connecting to the GTX970, however it always starts trying to use the new card instantly.
  • I also get a blank output on the GTX970 even with nomodeset enabled. However ideally I don't want the Linux Mint host to touch the GTX970 anyway other than for KVM to pass it to Windows.

Does anyone have any ideas how to proceed?

Ouki
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Lightning77
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    have you tried swapping the cards into each other's PCI-e slots? it may be that the system is booting on the 970 because it is detecting it first (due to it being in a lower numbered pci slot). worth testing, anyway. – cas Apr 14 '16 at 06:00
  • I haven't tried that yet but I will, I just more less placed the bigger card in a slot where I felt it would get more airflow – Lightning77 Apr 14 '16 at 06:02
  • Unfortunately I wasn't able to put the card in another slot because of the way the SATA connectors are positioned, the card would block the connectors, I did make progress though by booting my old card first long enough to install nvidia drivers for Linux, and then putting the GTX970 back in. – Lightning77 Apr 16 '16 at 00:02
  • does it boot now with both cards and the proprietary nvidia drivers rather than nouveau? – cas Apr 16 '16 at 00:09
  • It is booting with the correct drivers, and both card are detected but I only get output from the gtx970 – Lightning77 Apr 18 '16 at 05:10
  • Have you tried adding a `BusID "bus-id"` option (where "bus-id" is the pci bus id of your GT640 from, e.g., `lspci`) to the Devices section in your `/etc/X11/xorg.conf`? Given your unusual situation (two video cards, but you only want to use one in linux itself) you can't get away with not having an `xorg.conf` file and relying on the default/detected settings. You need to tell X explicitly what to do and which card to use. See `man xorg.conf`. And you'll also have to read the docs for the `nvidia` proprietary driver. – cas Apr 18 '16 at 07:34
  • FYI, these may help: https://wiki.debian.org/VGAPassthrough and https://forums.linuxmint.com/viewtopic.php?t=212692 and https://www.pugetsystems.com/labs/articles/Multiheaded-NVIDIA-Gaming-using-Ubuntu-14-04-KVM-585/ – cas Apr 18 '16 at 07:39
  • Thank You, Its working now, i3 is using the gt640, if i go to a tty shell it still comes up on the GTX970 but the system shows the card as unused, hopefully it wont interfere as long as I don't open a tty. – Lightning77 Apr 22 '16 at 22:01

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