As a fun experiment I have been struggling for a while now trying to use a box with 3 x NVS 510 videocards to drive a 3x3 videowall using Debian 10 Buster and ideally xrandr 1.5 (instead of the old Xinerama way).
I feel like I just need a solid foodhold, but here is where I am so far:
To simplify everything I’ve done, I’ll delete xorg.conf and run the following command:
nvidia-xconfig --sli=Mosaic --metamodes="GPU-0.DP-0: 1920x1080+0+0, GPU-0.DP-1: 1920x1080+1920+0, GPU-0.DP-2: 1920x1080+3840+0, GPU-0.DP-3: 1920x1080+0+1080, GPU-1.DP-0: 1920x1080+1920+1080, GPU-1.DP-1: 1920x1080+3840+1080, GPU-1.DP-2: 1920x1080+0+2160, GPU-1.DP-3: 1920x1080+1920+2160, GPU-2.DP-0: 1920x1080+3840+2160"
This is straight out of Chapter 30 of the README for this driver (460.73.01 from Buster-backports).
Central problem is that the Xorg log seems to totally disregard SLI and put me in BaseMosaic mode, which doesn’t work either. The pertinent section from the X log is here:
[ 720.009] (**) NVIDIA(0): Depth 24, (--) framebuffer bpp 32
[ 720.009] (==) NVIDIA(0): RGB weight 888
[ 720.009] (==) NVIDIA(0): Default visual is TrueColor
[ 720.009] (==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0)
[ 720.009] (**) NVIDIA(0): Option "SLI" "Mosaic"
[ 720.009] (**) NVIDIA(0): NVIDIA SLI Mosaic mode selected.
[ 720.009] (**) NVIDIA(0): Option "MetaModes" "GPU-0.DP-0: 1920x1080+0+0, GPU-0.DP-1: 1920x1080+1920+0, GPU-0.DP-2: 1920x1080+3840+0, GPU-0.DP-3: 1920x1080$
[ 720.009] (**) NVIDIA(0): Enabling 2D acceleration
[ 720.009] (II) Loading sub module "glxserver_nvidia"
[ 720.009] (II) LoadModule: "glxserver_nvidia"
[ 720.010] (II) Loading /usr/lib/xorg/modules/extensions/libglxserver_nvidia.so
[ 720.015] (II) Module glxserver_nvidia: vendor="NVIDIA Corporation"
[ 720.015] compiled for 1.6.99.901, module version = 1.0.0
[ 720.015] Module class: X.Org Server Extension
[ 720.015] (II) NVIDIA GLX Module 460.73.01 Thu Apr 1 21:35:16 UTC 2021
[ 720.015] (II) NVIDIA: The X server does not support PRIME Render Offload.
[ 720.016] (WW) NVIDIA(GPU-0): The "BaseMosaic" X configuration option should be used for
[ 720.016] (WW) NVIDIA(GPU-0): this configuration instead of the "SLI" "Mosaic" option.
[ 720.016] (WW) NVIDIA(GPU-0): The "BaseMosaic" option will be assumed. Please see
[ 720.016] (WW) NVIDIA(GPU-0): Chapter 30: Configuring SLI and Multi-GPU Mosaic and
[ 720.016] (WW) NVIDIA(GPU-0): Appendix B: X Config Options for more information.
[ 720.017] (II) NVIDIA(GPU-0): NVIDIA SLI enabled.
[ 720.017] (EE) NVIDIA(GPU-0): Failed to select a display subsystem.
[ 720.017] (EE) NVIDIA(GPU-0): Only one GPU will be used for this X screen.
[ 720.017] (EE) NVIDIA(GPU-0): The NVIDIA graphics device PCI:2:0:0 is part of an active SLI
[ 720.017] (EE) NVIDIA(GPU-0): configuration and is currently unavailable for single GPU
[ 720.017] (EE) NVIDIA(GPU-0): rendering. Please see Chapter 30: Configuring SLI and
[ 720.017] (EE) NVIDIA(GPU-0): Multi-GPU Mosaic in the README for troubleshooting
[ 720.017] (EE) NVIDIA(GPU-0): information.
[ 720.017] (EE) *** Aborting ***
[ 720.017] (EE) NVIDIA(0): Failing initialization of X screen
[ 720.017] (II) UnloadModule: "nvidia"
[ 720.017] (II) UnloadSubModule: "glxserver_nvidia"
[ 720.017] (II) Unloading glxserver_nvidia
[ 720.017] (II) UnloadSubModule: "wfb"
[ 720.017] (II) UnloadSubModule: "fb"
[ 720.017] (**) NVIDIA(G0): Depth 24, (--) framebuffer bpp 32
[ 720.017] (==) NVIDIA(G0): RGB weight 888
[ 720.018] (==) NVIDIA(G0): Default visual is TrueColor
[ 720.018] (==) NVIDIA(G0): Using gamma correction (1.0, 1.0, 1.0)
[ 720.018] (**) NVIDIA(G0): Option "SLI" "Mosaic"
[ 720.018] (**) NVIDIA(G0): NVIDIA SLI Mosaic mode selected.
[ 720.018] (WW) NVIDIA(G0): SLI is available only on screen 0. Disabling SLI.
[ 720.018] (EE) NVIDIA(G0): Only one X screen is supported when SLI is enabled. Disabling
[ 720.018] (EE) NVIDIA(G0): this screen.
[ 720.018] (EE) NVIDIA(G0): Failing initialization of X screen
[ 720.018] (II) NVIDIA(G1): (GPU-2) already has an X screen assigned; skipping this GPU
[ 720.018] (II) NVIDIA(G1): screen
[ 720.018] (EE) NVIDIA(G1): Failing initialization of X screen
[ 720.018] (II) UnloadModule: "nvidia"
[ 720.018] (II) UnloadSubModule: "wfb"
[ 720.018] (II) UnloadSubModule: "fb"
[ 720.018] (II) UnloadModule: "nvidia"
[ 720.018] (II) UnloadSubModule: "wfb"
[ 720.018] (II) UnloadSubModule: "fb"
[ 720.018] (EE) Screen(s) found, but none have a usable configuration.
[ 720.018] (EE)
Fatal server error:
[ 720.018] (EE) no screens found(EE)
[ 720.018] (EE)
Please consult the The X.Org Foundation support
at http://wiki.x.org
for help.
[ 720.018] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[ 720.018] (EE)
[ 720.019] (EE) Server terminated with error (1). Closing log file.
I cannot figure out why it’s refusing to support the SLI mode explicitly recommended in Nvidia’s documentation. Can anyone point me to something I’m missing?