[Bug 2859] Flickering or blanking on DVI output of Radeon 9200/9250

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Thu Jul 10 07:35:31 PDT 2008


--- Comment #106 from Alex Deucher <agd5f at yahoo.com>  2008-07-10 07:35:30 PST ---
(In reply to comment #105)
> Grabbing ModeLines from Xorg.log and setting them in xorg.conf won't work at
> all.
> They are ignored. Modified config and logfile attached.

I think that was a bug in xserver 1.3.0.  xserver 1.3.0 also had a bug where it
would reverse the sync polarity on modes from the edid.  you might want to
check if your xserver has been patched.

> There is mode override in 'configure kdesktop / display'. But 'Apply settings
> on KDE startup' is off.
> If I set 1024x768 in xorg.conf and press ctrl+alt+backspace monitor switches to
> that res.
> Did I miss something?

you can also add modelines on the fly with xrandr.  for example:
xrandr --newmode "1280x1024R"   90.75  1280 1328 1360 1440  1024 1027 1034 1054
+hsync -vsync
xrandr --addmode VGA-0 "1280x1024R"
xrandr --output VGA-0 --mode "1280x1024R"

> Lucky I can change modes (and vsync) by xrandr tool.
> 1280x1024 at 60Hz - default, screen jumps only on user input,
> 1280x1024 at 72Hz - screen jumps without user input, sometimes stops,
> 1280x1024 at 75Hz - screen jumps all the time.

you might also try the 1280x1024 at 59.9Hz

> Underclocking video output might "solve" problem.
> Is it a proper soltion?

It depends.  lots of LCD monitors are very picky about the signal they like. 
the wrong combination of dividers, even though it produces the proper dotclock
can make some monitors unhappy.  As such some video cards need to produce a
slightly different signal to make them happy in some circumstances.

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