Multiple screens.

Alex Deucher alexdeucher at
Mon Apr 4 13:37:03 PDT 2005

On Apr 4, 2005 4:21 PM, Peter Ankerstål <uchman at> wrote:
> > doesn't matter.  dualhead and clone work the same way.  The only
> > difference is the framebuffer offsets for the crtcs.  They are either
> > the same (clone) or different (dualhead).
> >
> > Alex
> >
> I can run both screens in 1024x768 (max for the interna screen) if I start X with
> the laptop lid(?) open.
> But I want to be able to switch to the external screen without restarting X.

Yes, crtc1 is driving both displays.  both the LCD and the VGA port
are getting the same mode, probably 1024x768 at 60hz.  If you want to run
the LCD at say 1024x768 at 60hz and the VGA port at say 1280x1024 at 75hz,
you will need to program both crtcs (crt/display controllers); one for
each output.  if you just want to use one crtc to drive either the vga
port or the lcd, there's not really an easy way to use modes beyond
the capabilites of the attached monitors after X is started.


> --
> Peter Ankerstål.

More information about the xorg mailing list