[CentOS] Re: screen shifting -- match monitor sections if Linux, otherwise use xvidtune

[Bryan J. Smith]

Daniel Wright <dw at wonderwave.net> wrote:
> Ya, the other computer is Windows XP. 

Hence the problem.

By default, Microsoft is good about following the VESA
standard modes.  Of course, this means you're typically
getting 56-60Hz refresh rates, with the rare 70 or 72Hz.
As such, most video card vendors have drivers that use other
rates, but they are very, very arbitrary.

XFree/Xorg pretty much uses the best scan rates of the
monitor, dynamically matching them up against many, many of
its own modelines.  In the "good ole days" we had to manually
define those modelines.  But not in recent years.

But if you want the XFree/Xorg modelines to match up against
the arbitrary ranges that your Windows driver is passing,
then you have to write those modelines manually.  The easiest
way is to use the monitor with the Windows sytem, then switch
to Linux at the same resolution, fire off xvidtune and it
will give you the required values.

See the XF86Config/xorg.conf man page for more information on
writing modelines.  You put them in your "Monitor" section. 
An example for a 1400x1050 line might be as follows:  
  ModeLine "1400x1050" 122.61 1400 1488 1640 1880 1050 1051
1054 1087  
Syntax being:  
  ModeLine "identifier" dotclock horz0 vert0 horz1 vert1 ...
 
> When running xvidtune this is what I get:
> Vendor: Monitor Vendor  Model: Dell1704FPV (Analog)
> num hsync:1, num vsync:1
> hsync range 0: 30.00 - 81.00
> vsync range 0: 56.00 - 76.00
> Video are not settable on this chip

Not good.  What video card / driver?

> What does the last line mean?  And with these settings what
> would my monitor lines look like in xorg.conf with these
> settings? This is what it looks like now:
> Section "Monitor"
>         Identifier   "Monitor0"
>         VendorName   "Monitor Vendor"
>         ModelName    "Dell 1704FPV (Analog)"
>         DisplaySize  340        270
>         HorizSync    30.0 - 81.0
>         VertRefresh  56.0 - 76.0
>         Option      "dpms"
> EndSection

You would put modelines in this section.

> Sorry for my ignorance, I usually don't install X.



> On the windows machine, my settings are 1280x1024 at 75Hz
> refresh rate if that helps.

Nope, it doesn't at all.  Vertical refresh is just one small
part of the equation.

The full equation is:  

  Bandwidth aka "DotClock"
    = Horizontal Frequency x Vertical Refresh
  Horizontal Size (obvious)
  Vertical Size (obvious)
  And various timings and options for exact placement,
    which will vary by card/monitor.

xvidtune makes it easy.

It let's you reposition and gives you all those values in a
point'n click GUI.


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