ATI Mobility Radeon X600 - Dualhead Configuration

Alex Deucher alexdeucher at
Fri Jul 6 14:04:55 PDT 2007

On 7/6/07, Laganakos Vassilis <elfshadow at> wrote:
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> Hello all,
> I have a problem with my recently obtained TFT monitor. I don't know if
> this is the right place to post (sorry). I want to have it connected to my
> laptop and use both screens, the laptop's screen and the external
> monitor.
> I tried various configurations I found on the web, and up till now I can
> do one of the following:
>         - use *only* the laptop's lcd (at least it worked...)
>         - use *only* the external tft monitor
>         - use *both* using the same resolution on both
> The problem is that the lcd is a 4:3 (1400x1050) while the TFT is a wide
> 16:10 (1440x900). Since the 16:10 is not a VESA supported ratio, I
> managed to configure correct the wide monitor using ModeLine in
> xorg.conf
> To use both screens I use MergedFB. I create some "Device" sections in the
> xorg.conf that are identical, except the identifier, and some "Screen"
> sections, using each device in one of them. I then configure MergedFB in
> one of the Screens, and I also enabled MergedXinerama and
> MergedNonRectangular.
> The wide monitor although that is connected was not detected by the
> radeon driver, and I had to force the use of MergedFB. When I used the
>         Option          "MonitorLayout" "LVDS, TMDS"
> it was detected *but* not the DDC settings.
> The result is that I can get both monitors working with the nice option
> to be able to drag windows from one screen to another (I really like
> this :) ), *but* the same resolution is used on both, so one of them is
> not displaying things good.
> Now I saw in some forums that you can use the PanelSize option to
> explicitly state the resolution you want to be used in the specific
> screen. I used this and alternative the MetaModes but it led nowhere,
> But I spent a few days (mainly nights) to get this far... I don't know
> if it is possible, but can the radeon driver drive two monitors with the
> same card, that they use different resolution? I'm not sure if my
> xorg.conf is correct...
> I am using FreeBSD-6-Stable, Xorg 7.2, and radeon driver.
> Could please some help out, if he/she had the same case solved? I attach
> my current xorg.conf stripped down.

Your metamodes are reversed.  the first one needs to be the built in
panel and the second one would be the external port.  Also, TMDS is
for DVI connections.  Unless your laptop has a DVI port, you should be
using "LVDS, CRT" for monitorlayout.  Also mergedfb is configured
strictly with driver options.  It is not configured like
zaphod/xinerama dualhead mode.  If you want to use mergedfb remove the
second device and screen lines and sections from your config.  If DDC
is not working you can force the second head on by enabling the
mergedfb option and specifying hsync and vrefresh ranges for the
second head.  See the radeon man page for more on mergedfb options.


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