Some(5) questions about xrandr (using intel driver)

[CSJ]

Hi, I've encountered some questions about using xrandr.
Any information is very appreciated.

thanks.

1. How xrandr detect usable resolutions?
   Are they intersection of VBIOS and EDID?

2. Why xrandr list different resolution when using different video driver?
   When I specify vesa driver in xorg.conf, why the 'xrandr -q' result are
different from intel driver.
   (ex: When I use vesa driver, I can see 1024x768 )

3. Why xrandr resolutions listed are not the same with that listed in MS
Windows?
   (Both installed native driver)
   I use Intel native driver both on Linux and Windows, why usable
resolutions are not the same.
   (ex: It only list one resolution 1280x800 on Linux,
        but 1280x800, 1024x768, 800x600 on Windows (Dell E6410))

4. Why xrandr addmode works on one machine, but failed on the other machine?
   I have two different intel Arrandale notebooks that lack 1024x768
resolution,
   And I use 'gtf 1024 768 60' result for xrandr addmode.
   It works on one machine (i5 M540) but failed on the other machine (i5
M520).

5. Why on some resolution, the two side of screen are black?
   On one notebook that max resolution is 1280x800,
   and when I use xrandr to set resolution to 1024x768, two side of screen
are black.
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