How to set default monitor mode?

Alex Deucher alexdeucher at
Sat May 23 09:13:01 PDT 2009

On Sat, May 23, 2009 at 10:23 AM, Harald Braumann <harry at> wrote:
> Hi,
> Xorg starts up with mode 1856x1392 at 60Hz. I'd rather have
> 1280x1024 at 85Hz, instead. I tried to change the default by setting
> Modeline "1280x1024_85.00" ...
> Option "PreferredMode" "1280x1024_85_00"
> in the Monitor section in xorg.conf. However, this doesn't seem to
> work. I get the following warning in the log:
> (WW) RADEON(0): Option "PreferredMode" is not used
> and X still uses 1856x1392 at 60Hz.
> Am I doing something wrong, or is there a bug?

Your config file is not correct.  Since your card has two outputs, you
need to associate the monitor section(s) with a particular connector.
Currently, your monitor section is associated with the connector that
is not in use:

(II) RADEON(0): Output DVI-1 using monitor section Configured Monitor
(**) RADEON(0): Option "PreferredMode" "1280x1024_85.00"
(II) RADEON(0): I2C bus "DVI-1" initialized.
(II) RADEON(0): Output DVI-0 has no monitor section
(II) RADEON(0): I2C bus "DVI-0" initialized.
(II) RADEON(0): Output DVI-1 disconnected
(II) RADEON(0): Output DVI-0 connected
(II) RADEON(0): Using exact sizes for initial modes
(II) RADEON(0): Output DVI-0 using initial mode 1856x1392

Take a look at this page for more on how to set up monitor sections
for multiple outputs:
changing the identifier for your monitor to DVI-0 should do the trick.

Section "Monitor"
	Identifier	"DVI-0"
	Modeline "1280x1024_85.00" 157.50 1280 1344 1504 1728 1024 1025 1028
1072 +HSync +VSync
	Option "PreferredMode" "1280x1024_85.00"

Section "Screen"
	Identifier	"Default Screen"
	Monitor		"DVI-0"

The xserver mode selection code should probably also be adjusted.
Picking 1856x1392 by default seems like the wrong choice.


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