External video - Toggle or both ?

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I have a Dell Latitude D505.
If I conect my external projector, I can toggle the display
    either onto the laptop screen
    or out to the video projector.

But, apparently, not on both simultaneously.

Some of my colleagues have opined that this is "not normal".
So i kinda mulled that over and I think I can remember seeing a machine that
did display both simultaneously.

What's the situation ?

With this material, can I have both ? If so, how so ?
And if not, whats the deciding factor?


Re: External video - Toggle or both ?

"Julian Woolian" <Julian.Woolian.net> writes:
Quoted text here. Click to load it

In order to drive two displays simultaneously with different content in
each, you need two separate areas of video RAM acting as frame buffers,
two different video timing generators (since in general the two monitors
are operating at different resolutions or frame rates), and two
different video D/A converters (or DVI outputs).  Most modern graphics
chipsets have all of those, and so you can have two different screens
active at once.

If your hardware doesn't have the duplicated resources described above,
then it can run only one display at a time, so it would have to switch
between the internal and external screens.

However, don't assume that FN-F8, or whatever keyboard shortcut your
laptop uses for switching video outputs, gives you all of the choices
your hardware is capable of.  Open up the Display Properties dialog box
and see if there really are two displays available (with an external
monitor plugged in), and what choices are available for configuring


Re: External video - Toggle or both ?

Thanks Dave.
To the point.
No waffle.

Julian Woolian

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