Help. x1600, dual monitors, DVI twitching

Alex Deucher alexdeucher at
Tue Sep 1 08:34:12 PDT 2009

On Thu, Aug 27, 2009 at 6:25 PM, Ron King<rking at> wrote:
> 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?

(II) RADEON(0): Port2:
  XRANDR name: DVI-0
  Connector: DVI-I
  DDC reg: 0x7e50

Your system uses DVO for the DVI port rather than one of the internal
TMDS transmitters.  I think this is the first system I've seen like
that.  I may need to add some additional code to make that work.  Can
you send me a copy of your video bios?

To capture the video bios (as root):
cd /sys/bus/pci/devices/<pci bus id>/
echo 1 > rom
cat rom > /tmp/vbios.rom
echo 0 > rom



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