[lug] Re: question on Xorg server configuration

Phil Rasch pjr at ucar.edu
Mon Jan 31 17:09:53 MST 2005

On Mon, Jan 31, 2005 at 01:54PM -0700, Michael J. Hammel wrote:
> > I have a series of questions that you all may be able to help me with?
> > 
> > 1) Can anybody tell me whether it is possible to display the same image 
> >    simultaneously on an internal and external display  generically using the 
> >    xorg server? And if so, can they offer me a generic xorg.conf file to
> >    do so?
> What exactly do you mean by "internal" and "external"?  On a laptop the
> LCD and external VGA are often connected via hardware and all that is
> required is to find the key sequence that points the video out both
> ports simultaneously.  I do that on my old (very old) IMB Thinkpad when
> I do talks using a projector.

I mean the LCD and a single external device (typically a projector). It
is frequently the case that notebooks running under linux require a
"software switch" rather than the "hardware switch" in order to display to 
both output devices simultaneously. For example I know this to be the 
case on 
1) fujitsu lifebooks (using the intel 855gm graphics)
2) ibm thinkpads (using a savage chip)
3) dell latitudes (ati radeon mobility
4) dell latitudes (with nvidia chips)

Each of those laptops allow some mechanism for toggling between external
and internal (LCD) displays via hardware (either Fn or closing the lid)
but each of them require a software solution on the linux side to get them
to display the same image to both devices simultaneously.

I have found solutions in the past for chips in classes 2, 3, 4 above, but
I am getting tired of it. If I can do it in the xserver it will make my
life easier. Each of the cases I cite required a different solution
(s3switch, "twinview" option on xserver, "clone" mode on ATI chipsets.)

Now I was looking for a solid generic way to do it that will work
whenever the graphics chip supports it, rather than searching yet again
for another kludge.

By the way, a single 855gm chip can essentially do the "xinerama"
option on two monitors with no problems, for the configurations you
mentioned. But I want the mirroring and I havent figured out a way to
do it yet.


> > much stuff deleted.

Phil Rasch, Climate Modeling Section, National Center for Atmospheric Research
Mail     --> P.O. Box 3000, Boulder CO 80307  
Shipping --> 1850 Table Mesa Dr, Boulder, CO 80305
email: pjr at ucar.edu, Web: http://www.cgd.ucar.edu/cms/pjr Phone:303-497-1368, FAX: 303-497-1324 

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