I have spent several hours fiddling with different xorg.conf configurations without getting a different image on my monitors.
My setup uses an on-board Radeon chipset HD4200. This provides both DVI and VGA sockets. I have monitors connected to both.
Because I am using the proprietary AMD driver, device 0 appears as "aticonfig-Device[0]-0"
I made the following changes to my vanilla xorg.conf:
In Section "ServerFlags" I added the line:
Option "Xinerama" "true"
In Section "Monitor" (for monitor1) I added the line:
Option "RightOf" "aticonfig-Monitor[0]-0"
I identified that BusID should be 1.5.0 and 1.5.1 respectively.
The device0 section already had BusID "PCI:1:5:0".
In Section "Device" for the second one I added
BusID "PCI:1:5:1"
In one of Sections "Screen" Under subsection "Display"
I added:
Modes "1280x1024"
Virtual 2560 1024
Xinerama appears to be installed in one or more several library file.
None of these things made any difference. So what have I either done wrong or
not yet done? (Apologies for my abruptness.)