Dual monitor configuration with radeon driver (radeon 9800 (pro))

[Erik Sundin <lassiethebrave@gmail.com>]

I'm trying to configure two monitors to work with a radeon 9800 (pro) card
using the radeon driver (mostly because fglrx no longer supports this
card...)
Starting up kdm or gdm with no xorg.conf leaves the screen connected to
DVI-0 blank and it remains so after login.
Using grandr doesn't do anything, I get this error:
"""
  The program 'grandr' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
  (Details: serial 46 error_code 8 request_code 149 minor_code 21)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
"""
When trying to change layout or anything.
xrandr reports the following:
"""
 Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 1366 x 1366
VGA-0 connected 1024x768+0+0 (normal left inverted right x axis y axis)
410mm x 230mm
   1366x768       59.8 +
   1280x720       75.0     60.0
   1152x720       60.0
   1024x768       75.0*    60.0
   1024x576       60.0
   832x624        74.6
   800x600        75.0     60.3
   640x480        75.0     59.9
   720x400        70.1
DVI-0 connected 1024x768+0+0 (normal left inverted right x axis y axis)
338mm x 270mm
   1280x1024      60.0 +   75.0     60.0
   1152x864       75.0
   1024x768       75.0*    60.0
   832x624        74.6
   800x600        75.0     60.3
   640x480        75.0     59.9
   720x400        70.1
S-video disconnected (normal left inverted right x axis y axis)
"""
The monitor at VGA-0 is supposed to be run at 1366x768 so i use "xrandr
--output VGA-0 --mode "1366x768"" to make it so;
Imagine my surprise when setting this resolution puts a cloned image
on the DVI-0 output!
so I figure "this might just work" and try "xrandr --output VGA-0
--pos 0x0 --output DVI-0 --right-of VGA-0"
and of course I get:
"""
  xrandr: screen cannot be larger than 1366x1366 (desired size 2390x768)
"""
I'm not getting why the screen is limited to 1366x1366 but I'm certain
there is a good reason and I'm definately not getting how I should
proceed with this...

Is there some way to change the "maximum screen size"? or maybe add
another screen? (I never did get the monitor-screen-desktop-display
thingy in Xorg right, sorry)
that is: Screen 0 on VGA-0 and Screen 1 on DVI-0.
pherhaps I should read man pages...

I've also tried with some xorg.conf files found on different sites,
these all lead to X not starting at all. if there is interest I could
provide these and the logs they generated...

//Erik Sundin