[Bug 17215] Screen resolution issues with Radeon Mobility 7500 unless NoDDC specified

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=17215





--- Comment #1 from Alex Deucher <agd5f at yahoo.com>  2008-08-20 07:50:55 PST ---
It's using DDC (Display Data Channel) to get the EDID (Extended Display
Identification Data).  DDC is the method by which an EDID is obtained.  
The EDID is list of supported modes and features from the monitor.  Generally
LVDS panels only support one resolution: the native mode of the panel.  Other
modes are supported by scaling a non-native mode to the native mode of the
panel using the scaling hardware.  In the cases where a monitor provides an
EDID, we use that data since it should contain the monitor's preferred
modelines.  In monitors without an EDID, we attempt to add the modes in the
display subsection of screen section of the config.

You can add new modes at run time using xrandr:
xrandr --newmode 1024x768   63.50  1024 1072 1176 1328  768 771 775 798 -hsync
+vsync
xrandr --addmode LVDS 1024x768


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