Set up two monitors in Linux?

Question

linux

Help a Linux newbie. Installed openSUSE 12.2 (x86_64) KDE: 4.8.
Hardware:
nVidia GeForce 7300 GS video card, DVI and DVI outputs.
Monitors Samsung SyncMaster 940N, one connected via DVI, the second one via an adapter to DSUB.
You need a resolution of 1280x1024 on both monitors, an extended desktop (not a clone)
In "System Settings" - "Display" - "Resolution and Orientation" there are two monitors, but for some reason one has a maximum resolution of 1280x1024, and the second one has 1024x768, although they themselves monitors are exactly the same.
tried with xrandr:

linux-4b34:/home/tomasina # xrandr
Screen 0: minimum 8 x 8, current 2560 x 1024, maximum 4096 x 4096
VGA-0 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768       60.0*+
   800x600        72.2     60.3     56.2  
   640x480        59.9  
   512x384       120.0  
   400x300       144.4    120.6    112.7  
   320x240       120.1  
DVI-I-0 connected 1280x1024+1024+0 (normal left inverted right x axis y axis) 376mm x 301mm
   1280x1024      60.0*+   75.0  
   1280x960       60.0  
   1152x864       75.0  
   1024x768       75.0     70.1     60.0  
   800x600        75.0     72.2     60.3     56.2  
   640x480        75.0     72.8     59.9  
TV-0 disconnected (normal left inverted right x axis y axis)

linux-4b34:/home/tomasina # xrandr --newmode "1280x1024_60"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync

linux-4b34:/home/tomasina # xrandr --newmode "1280x1024_60.0"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync

linux-4b34:/home/tomasina # xrandr --addmode VGA-0 "1280x1024_60"
X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  154 (RANDR)
  Minor opcode of failed request:  18 (RRAddOutputMode)
  Serial number of failed request:  31
  Current serial number in output stream:  32

Where is the mistake?
I read this wiki.archlinux.org/index.php/Xrandr#Adding_undetec... and the like, I did not find a solution.
I went the other way - I made changes to /etc/X11/xorg.conf.d/50-screen.conf (as far as I could figure it out):

Section "Device"
  Identifier "nvidia"  
  Driver         "nvidia"
  VendorName     "NVIDIA Corporation"
  BoardName      "GeForce 7300 GS"
  Option "VGA-0" "Monitor0"
  Option "DVI-I-0" "Monitor1"
EndSection

Section "Monitor"
  Identifier "Monitor0"
  Option     "PreferredMode" "1280x1024"
EndSection

Section "Monitor"
  Identifier "Monitor1"
  Option     "PreferredMode" "1280x1024"
  Option     "RightOf"   "Monitor0"
EndSection

Section "Screen"
  Identifier "Screen0"
  Device "nvidia"
  Monitor "Monitor0"
  DefaultDepth  24
  SubSection "Display"
    Virtual 2560 1024
  EndSubSection
EndSection

After the reboot, there is no effect, visually nothing has changed, no new permissions have been added.

Answer 1

I changed the cable, everything worked from the first kick. This is how you live in the age of digital technology, and sometimes you dance with a tambourine not where the dog rummaged.

Answer 2

It needs to be configured via nvidia utility.

Answer 3

the problem is that through the adapter it is impossible to read the EDID of the monitor and, accordingly, understand its parameters,
something like
Option "CustomEDID" "DVI-I-0: /etc/X11/edid.bin"
will help correct the situation
, well, it’s clear that edid is first needed save to a file (like this can be done through nvidia-settings)