[Bug 16846] second monitor doesn't light up on an Radeon Xpress 200M

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Mon Jul 28 17:55:28 PDT 2008


--- Comment #5 from Jonny Lamb <jonnylamb at jonnylamb.com>  2008-07-28 17:55:27 PST ---
Right, here's lots of information. I've tried to be as verbose as possible to
properly explain what I'm doing. I'm sorry it's a long read!

If I boot the laptop with the monitor connected it shows all the "ThinkPad
screen" plus grub et al. on both monitors. When X starts, the same thing
continues, with VGA-0 being a nice mirror image of LVDS. In xrandr, VGA-0 gives
many possible modes. The possible modes are: 1280x960, 1280x800, 1152x864,
1280x768, 1024x768, 832x624, 800x600, 640x480, 720x400 and 640x350. The
possible modes of LVDS stay constant at 1024x768, 800x600 and 640x480. "xrandr
--output VGA-0 --off" does work, and switching it back on is also successful.
If on the default mode of 1024x768, I use "xrandr --output VGA-0 --mode
800x600", VGA-0 continues to show at 1024x768 (the same as LVDS) and xrandr
shows the selected mode as being 800x600. If I try to use "xrandr --output
VGA-0 --left-of LVDS --auto" then I get the "screen cannot be larger than AxB"
message. If I add the "Virtual" entry in my xorg.conf under "Section Screen"
and "SubSection "Display"", the "cannot be larger than AxB" message disappears,
and there is clearly two displays, but both monitors are cloned on the same
display. I can easily tell there are two displays, or the screen has been
extended because I can lose my mouse off the edge of the screen.

If I boot the laptop *without* the monitor connected, it obviously boots up all
on LVDS. When X is started, xrandr successfully tells me that VGA-0 is
disconnected. If I plug in the monitor cable, another call to xrandr shows me
that VGA-0 is online, and shows the same modes as listed before for both VGA-0
and LVDS. Calling "xrandr --output VGA-0 --auto" powers up the external
monitor, and clones LVDS successfully, EXCEPT that the picture on VGA-0
horribly vibrates from side-to-side. If I use "--mode 800x600", the same
behaviour as above happens. Calling "--left-of LVDS" also shows exactly the
same behaviour as above: it outputs the "cannot be larger than" message
normally, and with "Virtual 2048 2048" it creates two displays, but only shows
one on both monitors. The picture vibration still occurs through all of these
steps if the monitor is not plugged in at bootup.

Pressing Fn+F7 (the key for changing monitor behaviour) doesn't do anything
when the machine is booted, but for some seconds on bootup it does allow to
switch between: showing picture on LVDS only, showing picture on VGA-0 only,
and showing picture on both. I conducted the above tests with the latter option
as the bootup was shown on both monitors. If I select the option of only
showing the bootup on LVDS, the VGA-0 is powered off for bootup but is powered
up when X starts. It mirrors LVDS as usual when X is started (and stops doing
so when X is stopped). Exactly the same thing happens if I boot up *without*
the external monitor plugged in. The picture vibration also continues to occur.

So, to sum up:
 * Pressing Fn+F7 makes no difference to X behaviour.
 * The picture is cloned whatever is asked for.
 * The resolution of the external monitor does not change if requested, but
reports a different resolution in xrandr.
 * The "Virtual" line in xorg.conf is required to even attempt --left-of.
 * When the machine is not booted up with the cable attached, the picture
vibrates from side-to-side horribly.

Thank you. I hope this is of some help.

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