Re: Why bother turning laptop ext. video off?

Andrew Smallshaw wrote:

On 2009-03-09, Robert Kaiser <spam-goes@xxxxxxxx> wrote:

The main reason why I was asking is because one of the laptops
I use for presentations (an older Thinkpad) apparently can not
be coerced to turn the external display on manually under Linux
and the generally accepted solution seems to be to keep it on
at all times by configuring the X server suitably.

With all of the Thinkpads I've seen you can toggle between
internal/external/dual video by pressing Fn-F7. I have a TP 600
here that does that and ISTR the 560 does it as well - both fairly
old models now.

Well, it doesn't work on mine (T40). I also have an X40 where it doesn't
work either. For the X40, I was able to locate a small C program that does
the trick. With some 1-2 days of googling and fiddling, I could probably
get that program to execute on Fn-F7, but so far, I'm just running it
from the command line (as I said: it's a pain..).

For both X40 and T40, external video works if a monitor/projector
is connected on bootstrap, so the BIOS apparently detects
that there is a load connected and turns the video on.

I don't know exactly how it is implemented but it
works fine in NetBSD without specific software support for it.


I also had some (now *very* old) laptops where this used to work
out of the box regardless of operating system. Those were pre-ACPI
(APM) BIOS models. I believe with APM BIOSes, the switching was
handled by the BIOS completely, the OS didn't get involved.

Cheers

Rob
.

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