Help. x1600, dual monitors, DVI twitching

Ron King rking at
Fri Aug 7 08:55:55 PDT 2009

Thanks for the try, but that's a no go.  If I use the radeonhd driver 
and attempt to set coherent_mode to false, all monitors blank.  If I set 
it in xorg.conf, the X server hangs.  With radeonhd the DVI output is a 
clone of LVDS, and both Xrandr and xorg.conf fail when I try to 
ignore/turn off the LVDS output.  With the default radeonhd and radeon, 
I get the flickering and missing rows.  I pulled the xf86-video-ati, but fails with a syntax error on line 12017 with an unknown token 
XINERAMA.  Unless you, or someone, has a fairly quick fix, I'm going to 
drop Fedora 11 and load another flavor.  I think Ubuntu is still using 
the older server and drivers.


On 08/05/2009 02:10 PM, Alex Deucher wrote:
> On Wed, Aug 5, 2009 at 3:24 PM, Ron King<rking at>  wrote:
>> Hi,
>> I'm on Fedora 11, M56 x1600, X server 1.6.2-3, ATI driver 6.12.2-14.
>> Laptop with docking station and dual Samsung SyncMaster 940Be LCDs.
>> Docking station has one VGA and one DVI-D.  All works fine in XP, Fedora
>> 8 (using Xrandr 1.2, I believe).
>> LVDS and VGA work fine, alone or dual.  DVI produces a vertical twitch,
>> always.  Running the cursor up the screen shows missing horizontal
>> lines.  Modes appear to be correct and match published monitor modes.
>> Changing modelines with xorg.conf and Xrandr do not seem to have any
>> effects.  Adding modes in Xrandr and using them causes the monitor to
>> blank, then return and still report the same problem.   Monitor reports
>> 31.7kHz and 30Hz regardless of changes.  Is this mode hard coded for
>> DVI-D somewhere?
> It sounds like your monitor doesn't like dvi coherent mode.  try:
> xrandr --output DVI-0 --set coherent_mode 0
> xrandr --output DVI-0 --off
> xrandr --output DVI-0 --auto
> If that doesn't work, you might try the driver from xf86-video-ati git
> master.  The display issues may be due to underflow to the display
> controller.
> Alex
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the xorg mailing list