I have a Dell Inspiron 600m with ATI Radeon Mobility M9 video chip trying to
drive a Dell 2001FP monitor at 1600x1200 (it's native resolution) over DVI.
History: 1600x1200 over DVI mode works fine in XFree86 4.3.0. After switching
to Xorg 6.8.0, this mode no longer works. I switched back to XFree to verify
that it still works OK there on the exact same hardware and cables.
Some other modes (e.g. 1400x1050, 1280x1024) seem to work fine over DVI. I can
Ctrl-Alt-+ to switch between modes to get to one that works.
When trying to display 1600x1200 over DVI, the panel will intermittently "lock
on" to the signal and display a desktop for a second or two before blanking
again. During the brief time it is displayed, many "snowy" artifacts are
covering the image, but the desktop is recognizable. Accessing the
configuration menu on the monitor indicates that it is trying to interpret the
signal at a resolution of 1406x1200 (the first number varies randomly between
1404 and 1426). For what it's worth, the display does better at locking onto
the signal when the desktop is blank (i.e. a solid color). When there are
multiple windows open, it rarely, if ever, is able to display anything at al.
After starting up Xorg in this mode, if I then plug in a VGA connector and
display to the same monitor, the desktop is fine and the system is usable. It
seems that the VGA connector is getting a well formed signal but the DVI one is
not. I'm not even sure if the VGA connector is supposed to be getting a signal
since I start X without anything connected to it, but there it is.
I tried using 'radeontool' to dump some registers out, but the only one that
was different between Xfree and Xorg was the CRT2_DDC register (a.k.a. MONIDB)
which has a value of 0x30000 in XFree and a value of 0x300 in Xorg. This may
be a red herring since I've been messing with my xorg.conf file for two days
trying to get this working and I may have changed the config slightly since I
copied the basic stuff from my XF86Config-4 file.
I applied a patch that I found on this site which was related to monitor
detection, but it didn't seem to affect anything.
For reference, I've included a link to another description of the problem:
I'll attach my xorg.conf and Xorg.0.log files.
Created attachment 1185 [details]
I've tried various flavors of IgnoreEDID and HorizSync/VertRefresh with no
Created attachment 1186 [details]
Log file from Xorg
This log may include additional informational messages which I inserted into
the driver while debugging.
I wonder why DDC does not succeed for your monitor.
*** This bug has been marked as a duplicate of 1129 ***