Arch Linux

UnwillingFirehose

Member

From: UK

Registered: 2014-12-09

Posts: 17

Running four screens off two nvidia cards

Hi,

I have four monitors plugged into two cards, running xmonad.

The cards are:

03:00.0 VGA compatible controller: NVIDIA Corporation NV43 [Quadro NVS 440] (rev a2)
04:00.0 VGA compatible controller: NVIDIA Corporation NV43 [Quadro NVS 440] (rev a2)

With no xorg.conf at all, and the nvidia driver installed, both screens on the first card are active, and are two independent screens - i.e. there's no Xinerama, so I can change what's displayed on one monitor without changing what's displayed on the other. I'd like to extend that capability to all four screens.

The "edited highlights" of xrandr -q are:

Screen 0: minimum 8 x 8, current 3840 x 1080, maximum 4096 x 4096
DVI-I-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 510mm x 290mm
   1920x1080     60.00*+
   1680x1050     59.95 
DVI-I-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 510mm x 290mm
   1920x1080     60.00*+
   1680x1050     59.95 
DVI-I-2 disconnected (normal left inverted right x axis y axis)
DVI-I-3 disconnected (normal left inverted right x axis y axis)

I'm unable to make DVI-I-2 and DVI-I-3 "connect" using xrandr, so I've resorted to nvidia-settings and xorg.conf.

With nvidia-settings I've tried setting up each monitor as its own X-Screen, or running the monitors as two pairs using TwinView - in both cases all four screens are in use, but xmonad is only present on the primary screen, and xrandr only shows the primary screen in it's output as well... *but* I can move the mouse across all four screens, it changes to the X servers default X cursor when on any screen except the primary screen. So they're active in some way, but the X server isn't using them for reasons I've been unable to ascertain.

I've tried the nouveau driver, but it's very CPU/memory intensive for things like watching YouTube videos, and I could only get the same result as above - one screen "active" with the other three just displaying the mouse. This includes using ZaphodHeads, as per http://nouveau.freedesktop.org/wiki/Mul … orDesktop/ - but using the correct designations of "DVI-I-0" rather than "DVI-0".

I've been through more iterations of xorg.conf than I care to remember... so I need to "connect" DVI-I-2 and DVI-I-3 in some way in the setup without using xorg.conf, or figure out the magic xorg.conf option that means xrandr and xmonad can use all four screens, not just the first one.

I've been through all the multihead pages on the Wiki, as well as many online, screen detection is working - and they're all pretty new monitors so EDID and so on is all good.

I think I understand how this is meant to work - it feels like I'm missing something. There's some magic option or command that means "make xmonad start on all 4 screens" or "make xrandr 'see' all 4 screens".

Happy to supply output from xrandr or contents of Xorg.0.log in relation to specific configurations if that helps.

UnwillingFirehose

Member

From: UK

Registered: 2014-12-09

Posts: 17

Re: Running four screens off two nvidia cards

I can make all four screens work an intended if I enable Xinerama, but of course this is the old way of doing things, RandR isn't supported when I'm running Xinerama, and the old way doesn't give me the flexibility that xrandr does.

Any suggestions, or do I just want the Moon on a stick?

Lone_Wolf

Administrator

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 15,552

Re: Running four screens off two nvidia cards

A SLI Mosaic setup may be what you need, since you got 2 quadro cards of exact same type.
(with non-quadro cards, max amount of screens is 3, with different cards you can't use SLI ).

Arch Nvidia page has some info about it, nvidia readme gives more details.

---

Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

clean chroot building not flexible enough ?
Try clean chroot manager by graysky

UnwillingFirehose

Member

From: UK

Registered: 2014-12-09

Posts: 17

Re: Running four screens off two nvidia cards

I eventually gave up on this when the new 304 driver stopped giving me two screens, let alone four.

So I swapped out that card ( I was mistaken, it was one card with two GPUs ) for a Quadro 450 NVS so I can at least use the 340 driver... but I can't get that working on more than one screen either   I suspect that's something to do with the Displayport adapters I'm using though... there might be another post on here shortly....