I've always wanted to run dual video cards with linux. However, every time I try it I get really frustrated (because I don't really know what I'm doing with regards to X) and give up.

I wish it were as easy as windows, where you just click on a few dialogs and things come up magically. I struggled with this so mightily I could just really say #%@#$#@$ and be happy with dualhead on a single card. Fiddling with /etc/X11/xorg.conf and trying to start X and trying over and over again. I had to go back to the internet many times to look for more ideas to try... This is so 1980s with manual configuration files and very little feedback as to what's going wrong. And I like to think that I'm fairly techno savvy.

Knoppix works awesomely with a single video card with dual heads. ARandR is marvelous and "just works." However, things get tricky when you want to run multiple video cards.

So I've got two cards: a geforce 7300 pci-e card with 2 heads and a geforce mx420 pci card with vga.

Knoppix actually detects both perfectly and brings up a text display on both cards. The hard part is configuring the /etc/X11/xorg.conf file.

Here's what "works for me":

lspci

1:00.0 VGA compatible controller: NVIDIA Corporation G72 [GeForce 7300 LE] (rev a1)
03:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5754 Gigabit Ethernet PCI Express (rev 02)
04:02.0 VGA compatible controller: NVIDIA Corporation NV17 [GeForce4 MX 420] (rev a3)

card0 is the geforce 7300LE
card1 is the geforce mx420

so I need to know the actual outputs of each card, and you can see the pci BusID address by looking at /sys/class/drm

knoppix@Microknoppix:~$ ls -l /sys/class/drm
total 0
lrwxrwxrwx 1 root root 0 Nov 23 22:29 card0 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card0
lrwxrwxrwx 1 root root 0 Nov 24 05:26 card0-DVI-I-1 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card0/card0-DVI-I-1
lrwxrwxrwx 1 root root 0 Nov 24 05:26 card0-TV-1 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card0/card0-TV-1
lrwxrwxrwx 1 root root 0 Nov 24 05:26 card0-VGA-1 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card0/card0-VGA-1
lrwxrwxrwx 1 root root 0 Nov 24 05:26 card1 -> ../../devices/pci0000:00/0000:00:1e.0/0000:04:02.0/drm/card1
lrwxrwxrwx 1 root root 0 Nov 24 05:26 card1-TV-2 -> ../../devices/pci0000:00/0000:00:1e.0/0000:04:02.0/drm/card1/card1-TV-2
lrwxrwxrwx 1 root root 0 Nov 24 05:26 card1-VGA-2 -> ../../devices/pci0000:00/0000:00:1e.0/0000:04:02.0/drm/card1/card1-VGA-2

and

knoppix@Microknoppix:~$ cat /sys/class/drm/*/status
disconnected
disconnected
connected
connected
connected

so it's VGA-1 on card0, VGA-2 and TV-2 on card1 are connected


and excerpts from my xorg.conf from /etc/X11/xorg.conf

# /etc/X11/xorg.conf

Section "ServerLayout"
Identifier "XFree86 Configured"
Screen 0 "Screen0" 0 0
Screen 1 "Screen1" RightOf "Screen0"

Option "Xinerama" "true"
Option "Clone" "off"
Option "AIGLX" "true"

EndSection

Section "Monitor"
Identifier "Monitor0"
ModelName "Generic Monitor"
EndSection

Section "Monitor"
Identifier "Monitor1"
ModelName "Generic Monitor"
EndSection

Section "Device"
Identifier "Card1"
Driver "nouveau"
VendorName "All"
BoardName "All"
BusID "PCI:4:2:0"
Option "ZaphodHeads" "VGA-2"
EndSection

Section "Device"
Identifier "Card0"
Driver "nouveau"
VendorName "All"
BoardName "All"
BusID "PCI:1:0:0"
Option "ZaphodHeads" "VGA-1"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Card1"
Monitor "Monitor0"
EndSection

Section "Screen"
Identifier "Screen1"
Device "Card0"
Monitor "Monitor1"
EndSection

I got another monitor and wanted to hook it up to card 0, so I added a few things:


Section "ServerLayout"
Identifier "X.org Configured"
Option "Xinerama" "on"
Option "Clone" "off"
Screen 0 "Screen0" 0 0
Screen 1 "Screen1" RightOf "Screen0"
Screen 2 "Screen2" RightOf "Screen1" #added screen 2 here

InputDevice "Mouse0" "CorePointer"
InputDevice "Keyboard0" "CoreKeyboard"
Option "AllowEmptyInput" "off"
EndSection

Section "Monitor"
Identifier "Monitor2"
VendorName "Monitor Vendor"
ModelName "Monitor Model"
EndSection

Section "Device"
Option "ZaphodHeads" "VGA-1"
Identifier "Card0"
Driver "nouveau"
BusID "PCI:1:0:0"
Screen 0
EndSection

Section "Device"
Option "ZaphodHeads" "DVI-I-1"
Identifier "Card0-DVI"
Driver "nouveau"
BusID "PCI:1:0:0"
Screen 1
EndSection

Section "Screen"
Identifier "Screen2"
Device "Card0-DVI"
Monitor "Monitor1"
EndSection


note that if you set the wrong screen number (like Screen 1 instead of Screen 0) in the Section "Device" the configuration will not work and you will get a message like this in /var/log/Xorg.0.log

Xorg Screen 1 deleted because of no matching config

This is an easy fix, just swap the screen numbers until it works. So I tried Screen 0 for Section "Device" Identifier Card0-DVI", and it didn't work so I went with Screen 1 which did. Note that this Screen number in the Section "Device" refers to the screens "internally numbered" for each head on a given card, and does not have anything to do with the Section "Screen". That was something I found a bit confusing.


You can omit the Screen number in the Section "Device" but it will only display a clone of the other head on the card.

a few tips and tricks:

boot with "knoppix 2" and then use

X -configure (to have Xorg try to generate an autoconfiguration, it puts a heck of a lot of crud into the file, but it does show you some ideas and structure. I think it made 7 different devices and screens, duplicating the card 3 or 4 times for different drivers)

X -config <filename> (to have Xorg use a different file location than /etc/X11/xorg.conf)

X -retro (to test your xorg.conf with a checkerboard background and the retro X pointer because when you launch X, the background is black and there's no mouse pointer)

and also the CTRL+ALT+BACKSPACE keystroke to kill the X server.

less /var/log/Xorg.0.log to see any error messages
less /var/log/Xorg.0.log | grep EE (to see any error events)

So I'd do a bunch of edits with "emacs /etc/X11/xorg.conf", then save the changes, and then launch "X -retro" to test them out. I'd exit the X server with CTRL+ALT+BACKSPACE. Once I'd get a setup that would work, I'd save it and reboot knoppix normally. (and I removed the line at the top of xorg.conf that tells knoppix to autogenerate this file on reboot.) Also note that I'm using knoppix with a "persistent" imagefile so /etc/X11/xorg.conf persists through reboots.

You can also do the editing within X-windows if you're brave, just emacs /etc/X11/xorg.conf from a terminal window, then CTRL+ALT+BACKSPACE which will kill and relaunch the X session, reading in your new xorg.conf.

My full xorg.conf:

Section "ServerLayout"
Identifier "X.org Configured"
Option "Xinerama" "on"
Option "Clone" "off"
Screen 0 "Screen0" 0 0
Screen 1 "Screen1" RightOf "Screen0"
Screen 2 "Screen2" RightOf "Screen1"

InputDevice "Mouse0" "CorePointer"
InputDevice "Keyboard0" "CoreKeyboard"
Option "AllowEmptyInput" "off"
EndSection

Section "Files"
ModulePath "/usr/lib/xorg/modules"
FontPath "/usr/share/fonts/X11/misc"
FontPath "/usr/share/fonts/X11/cyrillic"
FontPath "/usr/share/fonts/X11/100dpi/:unscaled"
FontPath "/usr/share/fonts/X11/75dpi/:unscaled"
FontPath "/usr/share/fonts/X11/Type1"
FontPath "/usr/share/fonts/X11/100dpi"
FontPath "/usr/share/fonts/X11/75dpi"
FontPath "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType"
FontPath "built-ins"
EndSection

Section "Module"
Load "dbe"
Load "dri"
Load "dri2"
Load "extmod"
Load "glx"
Load "record"
EndSection

Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
EndSection

Section "InputDevice"
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/input/mice"
Option "ZAxisMapping" "4 5 6 7"
EndSection

Section "Monitor"
Identifier "Monitor0"
VendorName "Monitor Vendor"
ModelName "Monitor Model"
EndSection

Section "Monitor"
Identifier "Monitor1"
VendorName "Monitor Vendor"
ModelName "Monitor Model"
EndSection
Section "Monitor"
Identifier "Monitor2"
VendorName "Monitor Vendor"
ModelName "Monitor Model"
EndSection

Section "Device"
Option "ZaphodHeads" "VGA-1"
Identifier "Card0"
Driver "nouveau"
BusID "PCI:1:0:0"
Screen 0
EndSection

Section "Device"
Option "ZaphodHeads" "DVI-I-1"
Identifier "Card0-DVI"
Driver "nouveau"
BusID "PCI:1:0:0"
Screen 1
EndSection

Section "Device"
Option "ZaphodHeads" "VGA-2"
Identifier "Card1"
Driver "nouveau"
BusID "PCI:4:2:0"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Card1"
Monitor "Monitor0"
EndSection

Section "Screen"
Identifier "Screen1"
Device "Card0"
Monitor "Monitor1"
EndSection

Section "Screen"
Identifier "Screen2"
Device "Card0-DVI"
Monitor "Monitor1"
EndSection


Section "DRI"
Mode 0666
EndSection