BIOS mirroring mode

Protas Oleksiy at
Sat Sep 6 16:24:26 PDT 2008

Hi, guys,

Sorry for bothering that often but I need an advice from low-level X coders, 
because surfing the net only gave userish results. Let me outline the problem.
We have a laptop with 1280x800 native resolution. It gets connected to 
projector with a 1024x768 resolution. What I need is a cloned display. RandR 
plays fine but there is a tricky thing. Because 1024x768 is smaller than 
1280x800, the projector only displays a portion of the screen, not the whole. 
Setting 1024x768 on built-in LCD is a no-go, because it messes plasma 
workspace and looks awful on non-native resolution.
Now the question part. When the laptop goes up it uses BIOS to mirror the 
display output onto external VGA channel. It handles all rescaling tasks, etc. 
In Linux it is true up to X start, because the driver disables this ability 
and manages VGA output on its own.
I am wondering how can one enable this feature on a running X server? This 
*must* be possible, as Windows keeps this thing upon boot to GUI if the 
desktop is not expanded.
Could you hint me how this can be achieved or what needs to be coded in order 

Thanks in advance.
Protas Oleksiy
National University «Kyiv-Mohyla Academy»
Institute of Molecular Biology and Genetics, Ukraine
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