Hello,
I’ve spent a lot of time trying to get SLI enabled with two GeForce GTX 980 cards (Gigabyte GV-N980WF3OC-4GD) to render six monitors and just could not do it. One thing I’ve found has led me to question if the kernel has support for it those cards.
Per the documentation at Chapter 25. Configuring SLI and Multi-GPU FrameRendering
Verify that each GPU is connected to a bus connected to the Root Bridge (note that the GPUs in the above example are on buses 0a and 81):
% /sbin/lspci -t
good:
-+-[0000:80]-+-00.0
| +-01.0
| \-0e.0-[0000:81]----00.0
...
\-[0000:00]-+-00.0
+-01.0
+-01.1
+-0e.0-[0000:0a]----00.0
bad:
-+-[0000:81]---00.0
...
\-[0000:00]-+-00.0
+-01.0
+-01.1
+-0e.0-[0000:0a]----00.0
Note that in the first example, bus 81 is connected to Root Bridge 80, but that in the second example there is no Root Bridge 80 and bus 81 is incorrectly connected at the base of the device tree. In the bad case, the only solution is to upgrade your kernel to one that properly detects your PCI bus layout.
lspci -t for me shows:
-+-[0000:ff]-+-0b.0
| +-0b.1
| +-0b.2
| +-0c.0
| +-0c.1
| +-0c.2
| +-0c.3
| +-0c.4
| +-0c.5
| +-0f.0
| +-0f.1
| +-0f.4
| +-0f.5
| +-0f.6
| +-10.0
| +-10.1
| +-10.5
| +-10.6
| +-10.7
| +-12.0
| +-12.1
| +-13.0
| +-13.1
| +-13.2
| +-13.3
| +-13.4
| +-13.5
| +-13.6
| +-13.7
| +-14.0
| +-14.1
| +-14.2
| +-14.3
| +-14.6
| +-14.7
| +-15.0
| +-15.1
| +-15.2
| +-15.3
| +-16.0
| +-16.6
| +-16.7
| +-17.0
| +-17.4
| +-17.5
| +-17.6
| +-17.7
| +-1e.0
| +-1e.1
| +-1e.2
| +-1e.3
| +-1e.4
| +-1f.0
| \-1f.2
\-[0000:00]-+-00.0
+-01.0-[01]--
+-01.1-[02]----00.0
+-02.0-[03]--+-00.0
| \-00.1
+-03.0-[04]--+-00.0
| \-00.1
+-05.0
+-05.1
+-05.2
+-05.4
+-11.0
+-11.4
+-14.0
+-16.0
+-19.0
+-1a.0
+-1b.0
+-1d.0
+-1f.0
+-1f.2
\-1f.3
Which much more resembles the bad. Can anyone provide any insight?
Some additional info:
- Distro: Fedora 23
- Motherboard: ASRock X99 Extreme4 ATX LGA2011-3 Motherboard
xorg.conf:
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
Option "Xinerama" "0"
EndSection
Section "Files"
FontPath "/usr/share/fonts/default/Type1"
EndSection
Section "InputDevice"
# generated from default
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/input/mice"
Option "Emulate3Buttons" "no"
Option "ZAxisMapping" "4 5"
EndSection
Section "InputDevice"
# generated from default
Identifier "Keyboard0"
Driver "keyboard"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor0"
VendorName "Unknown"
ModelName "HP 27sv"
HorizSync 30.0 - 80.0
VertRefresh 50.0 - 60.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce GTX 980"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "Stereo" "0"
Option "nvidiaXineramaInfoOrder" "DFP-7"
Option "MultiGPU" "On"
Option "SLI" "Mosaic"
Option "MetaModes" "GPU-0.DFP-3: nvidia-auto-select +3840+1080, GPU-0.DFP-5: nvidia-auto-select +0+1080, GPU-0.DFP-7: nvidia-auto-select +1920+1080, GPU-1.DFP-0: nvidia-auto-select +0+0 {rotation=invert}, GPU-1.DFP-1: nvidia-auto-select +1920+0 {rotation=invert}, GPU-1.DFP-4: nvidia-auto-select +3840+0 {rotation=invert}"
SubSection "Display"
Depth 24
EndSubSection
EndSection