Linux xorg.conf Help

Preface this message by admitting I’m relatively new to Linux, and I’m not a programmer. I know just enough from watching online tutorials and reading FAQ’s to be dangerous.

I have two GeForce GTX 1080 cards in SLI, and I’m using Linux Mint 21.1 Cinnamon. I’ve been doing quite a bit of research on how to enable SLI in the NVIDIA Settings in Linux, and I know I have to go into the xorg.conf file and add this line (Option “SLI” “mosaic”), but I’m not sure what section it is to be added to - the “Device” (video card) section, as one tutorial showed it going in the “Screen” section.

My xorg.conf file also only has one Section “Device” (video card) listing showing Device0 (GPU 0), and I would expect to see another listing of Device1 (GPU 1).

On the right side of the screen in the NVIDIA Settings panel when highlighting “X Screen 0” in the left column, it only shows one GPU - GPU 0. On the left column listings it does show both GPU 0 and GPU 1, but only GPU 0 has overclocking available to be adjusted. GPU 1 doesn’t even show the options.

I did add in the Section “Device” (GPU0) section of code (Option “Coolbits” “12”) which enables overclocking, but I’m wondering if there needs to be another Section “Device” for GPU1 to be added with (Option “Coolbits” “12”) to enable overclocking on the second video card as well.

After enabling SLI in the xorg.conf file, I ran the Heaven benchmark and NVIDIA Settings showed 100% utilization for GPU0, and 0% for GPU1. That is why I’m wondering if there needs to be a section of code added in for the second video card, both for overclocking and for SLI to actually be enabled.

Anybody have any ideas or experience with this? Thank you in advance.

# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 525.105.17

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"

Section "Files"

Section "InputDevice"

    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"

Section "InputDevice"

    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    Option         "DPMS"

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    Option         "Coolbits" "12"

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "SLI" "mosaic"
    SubSection     "Display"
        Depth       24

SLI in terms of implicit multi-gpu rendering doesn’t exist anymore, it was removed years ago. It was broken and useless, anyway.

Not the most helpful reply. Does anyone have anything constructive to add?

If SLI doesn’t exist and was removed, why is NVIDIA still referencing it in the Read-Me for the latest driver?

I was speaking of “SLI in terms of implicit multi-gpu rendering”
The manual speaks of SLI Mosaic, i.e. video walls with quadro type cards.
The driver changelog:

2020-09-17 version 455.23.04
    * Removed support for the SLI modes "SFR", "AFR", and "AA".  SLI Mosaic,
      Base Mosaic, GL_NV_gpu_multicast, and GLX_NV_multigpu_context are still

Once again, my ignorance got the best of me. I found some articles indicating you were correct - the type of SLI I was hoping to use is no longer supported. I didn’t know there were so many different kinds of SLI, and my reading of the notes in the current NVIDIA driver regarding SLI made it sound to me like SLI “mosaic” was what I was wanting to enable and use. Turns out that is not the case. :(

Last night I was doing some more research on this and the last Linux driver I could find that still had the SLI I’m hoping for is NVIDIA-Linux-x86_64-450.119.03. I downloaded it to try and install it and see what happens. After all, this PC I built is for tinkering and learning how to do stuff like SLI and overclocking RAM and CPU. It’s been quite a learning experience for a non-Techie like myself, but I sure have learned a LOT thanks to all you helpful people online. I’ll call this thread closed since now I know it’s a driver issue. Now - if I can just figure out how to downgrade the video driver to the one I downloaded. Thank you for your help.

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