Arch Linux

ratdude747

Member

From: Madison, IN

Registered: 2013-07-05

Posts: 42

Nvidia SLI + Dual Montors: Doable?

I've been trying to get my main rig's GPU setup working correctly, and I've hit an impass.

I'm running twin GeForce 250 GTS's on a Tyan S2895 Thunder K8WE. My montors are a pair of 1280x1024 Dell Ultrasharps hooked by DVI to the the primary card. The SLI setup works fine in Windows 7.

I've gotten SLI to work but try as I might, I can't get anything from the second monitor (instead I get a single scrolling LCD). I'm setup to use twinview since both LCD's are on the same card.

All packages are up to date (I'm using the 340 driver). I will note that the install is a tweaked copy from a laptop of mine (I've been running arch on my laptops for ages); I doubt that's the issue though.

My xorg.conf:

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 340.58  (buildmeister@swio-display-x86-rhel47-09)  Fri Oct 31 17:39:45 PDT 2014

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

Section "Files"
EndSection

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

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "DELL 1703FP"
    HorizSync       30.0 - 80.0
    VertRefresh     56.0 - 76.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTS 250"
    BusID          "PCI:2:0:0"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "nvidiaXineramaInfoOrder" "DFP-0"
    Option         "metamodes" "DVI-I-2: 1280x1024 +0+0"
    Option         "SLI" "AUTO"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Suggestions? Or is it really true that one cannot do SLI with twin monitors in linux?

ratdude747

Member

From: Madison, IN

Registered: 2013-07-05

Posts: 42

Re: Nvidia SLI + Dual Montors: Doable?

Nailed it.

The trick was using MOASAIC, not twinview.

See my Xorg.conf for what changed:

# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 340.58  (buildmeister@swio-display-x86-rhel47-09)  Fri Oct 31 17:40:05 PDT 2014

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 340.58  (buildmeister@swio-display-x86-rhel47-09)  Fri Oct 31 17:39:45 PDT 2014

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

Section "Files"
EndSection

Section "InputDevice"

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

Section "InputDevice"

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

Section "Monitor"

    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "DELL 1703FP"
    HorizSync       30.0 - 80.0
    VertRefresh     56.0 - 76.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTS 250"
    BusID "PCI:2:0:0"
EndSection


Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "nvidiaXineramaInfoOrder" "DFP-0"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "On"
    Option         "SLI" "AFR"
    Option         "MetaModes" "GPU-0.DFP-0: 1280x1024+0+0, GPU-0.DFP-1: 1280x1024+1280+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Buddlespit

Member

From: Chesapeake, Va.

Registered: 2014-02-07

Posts: 507

Re: Nvidia SLI + Dual Montors: Doable?

All 'BaseMosaic' does is tie monitors together across video cards. You aren't running SLI if you have dual display working. It was purposefully disabled by Nvidia for all but quadro cards. You'll be able to verify this if you run unigine benchmarks. You'll see that the second card is just idling.

I spent a month trying to get a pair of gtx-550ti's to sli with my dual monitors because i refused to believe that it couldn't be done. I ended up giving up and buying a gtx-770.

---

An old man, trying to stay sane

ratdude747

Member

From: Madison, IN

Registered: 2013-07-05

Posts: 42

Re: Nvidia SLI + Dual Montors: Doable?

Funny, as Nvidia control panel showed both cards as being part of the display.

I couldn't get any of the unigine benchmarks to build (using aura)... but I did notice a performance level increase and hotter temps on both GPUs when playing minecraft. like 34C idle and 44-45C during minecraft. GPU 0 does get a lot hotter (62C), but GPU1 is clearly not idling either.

ratdude747

Member

From: Madison, IN

Registered: 2013-07-05

Posts: 42

Re: Nvidia SLI + Dual Montors: Doable?

Ran Unigine Heaven direct from the binary... GPU 0 got up to 67-68C, while GPU 1 Got to 61-62C. So no, GPU1 is NOT idling... so does that mean that SLI is in indeed working?

ratdude747

Member

From: Madison, IN

Registered: 2013-07-05

Posts: 42

Re: Nvidia SLI + Dual Montors: Doable?

That's where the temps leveled out after a minute or two of benchmarking.

Buddlespit

Member

From: Chesapeake, Va.

Registered: 2014-02-07

Posts: 507

Re: Nvidia SLI + Dual Montors: Doable?

You can check your Xorg.0.log and look for this:

(**) NVIDIA(0): Option "SLI" "on"
(**) NVIDIA(0): NVIDIA SLI enabled; using auto-selected rendering method.

That should let you know that it's working.

edit: Also, the Unigen benchmark should show both of your gpu's on the right side and you should be able to see if they match freqs.

Last edited by Buddlespit (2014-11-28 03:02:39)

---

An old man, trying to stay sane

ratdude747

Member

From: Madison, IN

Registered: 2013-07-05

Posts: 42

Re: Nvidia SLI + Dual Montors: Doable?

Unigen only showed the one GPU, not the second... but in journalctl (since I'm on GDM) I did find:

(**) NVIDIA(0): Option "SLI" "AFR"
(**) NVIDIA(0): NVIDIA SLI alternate frame rendering selected.

(since I had SLI not set to auto).

Base mosaic was also shown to have been setup successfully.

Buddlespit

Member

From: Chesapeake, Va.

Registered: 2014-02-07

Posts: 507

Re: Nvidia SLI + Dual Montors: Doable?

Ok, now copy your xorg.conf to xorg.conf.bak, disable a monitor in nvidia-settings and save to xorg.conf, reboot and check again. I honestly don't think you have sli running, just enabled.

---

An old man, trying to stay sane

ratdude747

Member

From: Madison, IN

Registered: 2013-07-05

Posts: 42

Re: Nvidia SLI + Dual Montors: Doable?

No change when disabled in xorg.conf. Nvidia settings had no effect (as it only removed the metamode, not the mosaic option). It also disabled SLI, which I also had to re-enable.

Short of trying it with just one card, IDK how one would tell. It was playing STK well if that means much... Given that my favorite keyboard isn't playing well, I may just go back to Windows 7 only on this rig (loaded with a bunch of FOSS software at least) and leave arch for my other rig (single 9800GT PE 1GB) and my laptops.

Physicist1616

Member

Registered: 2015-02-16

Posts: 37

Re: Nvidia SLI + Dual Montors: Doable?

I'm trying to do similar things, but slightly different.  My Windows 7 setup is 2 GTX 550 Ti's, cables coming from only one card to two different monitors (one HDMI TV across the room) that just mirror each other.  As far as I can tell, the SLI is completely functional in this setup.

On Arch, I want to do the exact same thing.  I know that the Xorg.conf plays a critical role here, but am still learning about the whole thing.

* What other config files come into play? 
* Does nvidia-settings only provide a gui for proper syntaxing into that one .conf?
* What file does my xfce4-display-settings change, and if it's Xorg.conf, does it play nicely with nvidia-settings?
* When I had LXDE, I noticed this amazing thing where it was piping audio through the video card to my HDMI TV.  How do I control this and make it happen now that I am running xfce4 (or any other display setup)?

I have made my intended setup work, but only temporarily, it had several manual steps each time I started X (and I can't figure out how do to it again now that I've switched to xfce4).  Rebooting made it go away anyway, so even though it worked, it was wrong.  Last time I wrote to xorg.conf, I lost the ability to display to both monitors at the same time period, and nvidia-settings changes aren't applying, I think because of some heavy-handed workings by xfce-display-settings. 

It's hard to know what settings menus are mutually exclusive, which do exactly the same things, and which provide unique features.  Any tips on that? 

I built up my Arch install faster than I could learn some of these things; I have half a mind to reinstall and see if I can learn more about the whole display 'stack'.