External monitor can only "copy" laptop's built-in

[Aviram Jenik]

I've had some success configuring xorg.conf or using the system settings 
configuration for the dual display. But that sometimes works, sometimes 
doesn't, and hard to know why (not to mention a reboot changes things back 
again) and very hard to give a 'recipe'. It seems to be very 
version-dependent or buggy to the point where it works for some people on 
some video cards, and may not work for others.

The best solution I could find is xrandr, as Omer mentioned. xrandr *always* 
worked for me, even in complex configurations.

Things to note: change the resolution/refresh rate of each screen to their 
maximum (start with xrandr -q to see where you stand, and then 
xrandr --output LVDS --mode YYYxZZZ). It also has switches to put one screen 
on the right or left of the other, and it all happens immediately. Of course, 
as Omer mentioned, make sure the virtual display settings are big enough for 
(1680+1680)x1050.

Also check out the 'addmode' switches that allow you to set a very specific 
configuration (refresh rate, etc) on each of the monitors to really make sure 
you are taking advantage of it.

The downside of xrandr is that you have to manually do it., and you lose the 
wonderful auto-detect features of xorg. Then again you can map it to a 
hot-key and make it work with a single click of a button.

- Aviram


On Friday 21 May 2010 07:55:43 Dotan Cohen wrote:
> I have a Dell Inspiron 6400 / 1505E with 1680x1050 built-in LVDS and
> external VGA connected to a 1680x1050 LCD monitor. I can get the
> external monitor to mirror the regular display, but I cannot put them
> side-by-side with the KDE System Settings tool.
>
> The KDE System Settings tool sees the external VGA monitor as the
> "first" monitor and the built-in LVDS as the "second". When I
> configure the LVDS to the right of the external VGA monitor, the LVDS
> goes blank. When I configure the LVDS to the left of the external VGA
> monitor, the external VGA goes blank.
>
> What must I do to get these monitors configured?
>
> I'm using Kubuntu 9.10, KDE 4.2.2. Thanks.