I was able to workaround this problem by switching from Xinerama to MergedFB. See randeon(4x) for details. This actually seems to be superior to Xinerama. I had to disable DRI for stability though. Attached is my xorg.conf as a reference.
-- Eric Dorland <[EMAIL PROTECTED]> ICQ: #61138586, Jabber: [EMAIL PROTECTED] 1024D/16D970C6 097C 4861 9934 27A0 8E1C 2B0A 61E9 8ECF 16D9 70C6 -----BEGIN GEEK CODE BLOCK----- Version: 3.12 GCS d- s++: a-- C+++ UL+++ P++ L++ E++ W++ N+ o K- w+ O? M++ V-- PS+ PE Y+ PGP++ t++ 5++ X+ R tv++ b+++ DI+ D+ G e h! r- y+ ------END GEEK CODE BLOCK------
# XF86Config-4 (XFree86 server configuration file) generated by dexconf, the
# Debian X Configuration tool, using values from the debconf database.
#
# Edit this file with caution, and see the XF86Config-4 manual page.
# (Type "man XF86Config-4" at the shell prompt.)
#
# If you want your changes to this file preserved by dexconf, only make changes
# before the "### BEGIN DEBCONF SECTION" line above, and/or after the
# "### END DEBCONF SECTION" line below.
#
# To change things within the debconf section, run the command:
# dpkg-reconfigure xserver-xfree86
# as root. Also see "How do I add custom sections to a dexconf-generated
# XF86Config or XF86Config-4 file?" in /usr/share/doc/xfree86-common/FAQ.gz.
Section "Files"
FontPath "unix/:7100" # local font server
# if the local font server has problems, we can fall back on these
FontPath "/var/lib/defoma/x-ttcidfont-conf.d/dirs/CID"
FontPath "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType"
FontPath "/usr/lib/X11/fonts/Type1"
FontPath "/usr/lib/X11/fonts/CID"
FontPath "/usr/lib/X11/fonts/Speedo"
FontPath "/usr/lib/X11/fonts/misc"
FontPath "/usr/lib/X11/fonts/cyrillic"
FontPath "/usr/lib/X11/fonts/100dpi"
FontPath "/usr/lib/X11/fonts/75dpi"
EndSection
Section "Module"
Load "GLcore"
Load "bitmap"
Load "dbe"
Load "ddc"
# Load "dri"
Load "extmod"
Load "freetype"
Load "glx"
Load "int10"
Load "record"
Load "speedo"
Load "type1"
Load "vbe"
EndSection
Section "InputDevice"
Identifier "Generic Keyboard"
Driver "keyboard"
Option "CoreKeyboard"
Option "XkbRules" "xorg"
Option "XkbModel" "pc104"
Option "XkbLayout" "us"
EndSection
Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/psaux"
Option "Protocol" "ImPS/2"
Option "Buttons" "7"
Option "ZAxisMapping" "4 5"
EndSection
Section "InputDevice"
Identifier "Generic Mouse"
Driver "mouse"
Option "SendCoreEvents" "true"
Option "Device" "/dev/input/mice"
Option "Protocol" "ImPS/2"
Option "Emulate3Buttons" "true"
Option "ZAxisMapping" "4 5"
EndSection
Section "Device"
Identifier "Radeon 9500 DVI"
Driver "radeon"
BusID "PCI:1:0:0"
Option "MonitorLayout" "TMDS,CRT"
Option "MergedFB" "true"
Option "MetaModes" "1280x1024-1280x1024"
Option "MergedXineramaCRT2IsScreen0" "false"
Option "CRT2Position" "LeftOf"
EndSection
Section "Device"
Identifier "Radeon 9500 VGA"
Driver "radeon"
BusID "PCI:1:0:0"
Screen 1
EndSection
Section "Monitor"
Identifier "SyncMaster 950p"
HorizSync 30-96
VertRefresh 50-160
#Option "DPMS"
EndSection
Section "Monitor"
Identifier "Viewsonic E790"
HorizSync 30-95
VertRefresh 50-200
Option "DPMS"
EndSection
Section "Monitor"
# Block type: 2:0 3:fd
# Block type: 2:0 3:fc
Identifier "L90D+ DVI"
VendorName "HIQ"
ModelName "L90D+ DVI"
# Block type: 2:0 3:fd
HorizSync 31-67
VertRefresh 59-61
# Max dot clock not given
# Block type: 2:0 3:fc
# DPMS capabilities: Active off:yes Suspend:yes Standby:yes
#Mode "1280x1024" # vfreq 60.020Hz, hfreq 63.981kHz
# DotClock 108.000000
# HTimings 1280 1328 1440 1688
# VTimings 1024 1025 1028 1066
# Flags "+HSync" "+VSync"
#EndMode
#Mode "800x600" # vfreq 60.317Hz, hfreq 37.879kHz
# DotClock 40.000000
# HTimings 800 840 968 1056
# VTimings 600 601 605 628
# Flags "+HSync" "+VSync"
#EndMode
# Block type: 2:0 3:fd
# Block type: 2:0 3:fc
Option "DPMS"
EndSection
Section "Screen"
Identifier "Main"
Device "Radeon 9500 DVI"
Monitor "L90D+ DVI"
DefaultDepth 24
SubSection "Display"
Depth 24
Modes "1280x1024"
# Virtual 2560 1024
EndSubSection
EndSection
Section "Screen"
Identifier "Left"
Device "Radeon 9500 VGA"
Monitor "SyncMaster 950p"
DefaultDepth 24
SubSection "Display"
Depth 24
Modes "1280x1024"
EndSubSection
EndSection
Section "ServerLayout"
Identifier "Default Layout"
# Option "Xinerama" "true"
Screen "Main"
# Screen "Left" LeftOf "Main"
# Screen "Left"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"
InputDevice "Generic Mouse"
EndSection
Section "DRI"
Mode 0666
EndSection
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