Help. x1600, dual monitors, DVI twitching

Ron King rking at
Thu Aug 27 15:25:47 PDT 2009

Alex Deucher wrote:
> On Fri, Aug 7, 2009 at 11:55 AM, Ron King<rking at> wrote:
>> 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.
> You need the xorg macros package.  Grab the build deps with yum.
> Alex
Ok, it seems that Ubuntu has the same problem.  I pulled the latest git 
and found the same issue.  I tried Alex's coherent_mode change, but it 
doesn't seem to have any effect at all.  I've attached the Xorg log.

My external LCD uses a DVI-D, single link.  Per the specs, VESA 1280 x 
1024 63.981 60.020 108.00 +h/+v  When I check the on-screen OSD, it 
reports that the horizontal rate is 32kHz and the vertical is 30Hz.  
These values are half what the manual specs for that mode.  Without 
delving into the code, I think it would seem that the driver is 
outputting a DVI-D dual link signal (>165MHz), rather than the expected 
single link (<165MHz) at 108.0MHz.  If this sounds reasonable, could 
someone point me to the relevant code so that I might change a few things?

-------------- next part --------------
A non-text attachment was scrubbed...
Name: Xorg.0.log
Type: text/x-log
Size: 456467 bytes
Desc: not available
URL: <>

More information about the xorg mailing list