radeon vs. flaky DDC / EDID of Samsung 214T

Csillag Kristof csillag.kristof at united-consult.hu
Tue Sep 8 16:48:00 PDT 2009

Dear all,

I am trying to use a Samsung SyncMaster 214T monitor with a radeon-based
graphics solution
(RS690M to be more specific.)

If I connect it via VGA, everything is fine - except the image quality,
of course. (See attached log.)

However, when connected via DVI, it's not detected neither by the BIOS
at boot time,
nor by Xorg. (See attached log.)

I have also tried to run get-edid, but it fails to produce any output.
(It also works fine when connected via VGA.)

   * * *

I am sure that the monitor can be forced to work:
if I got the DVI output configured (by having a different monitor
connected at boot time or at X start time), and than remove the original
and connect the 214T,  both the linux console and Xorg works.

        * * *

The problem is definitely with the monitor: if I connect the same
monitor to an Nvidia card
(using the proprietary driver), the monitor can be detected via DDC, but
the EDID
can not be properly read. The only way to use the monitor properly with
Nvidia is to
capture the EDID while connected via VGA, and forcing the Nvidia to use
the captured EDID
info when using the monitor via DVI, by using the CustomEDID option in
the xorg.conf file.

    * * *

I would like to use this monitor with my radeon card, via DVI. How do I
do that?

I have tried to fiddle around the various options (IgnoreEDID, noDDC),
but the
monitor is still not detected. Is there a way to force driving the
output in a specified
way, regardless of the DDC detection?

I remember fglxr has something like "MonitorLayout" which can be used to
monitor types, but I would like to stay with the Radeon driver.

Thank you for your help:

    Kristof Csillag

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