Force the X refresh rate

Nifty Hat Mitch mitch48 at sbcglobal.net
Fri Jan 28 02:30:13 UTC 2005


On Thu, Jan 27, 2005 at 08:02:58AM +0100, Eric Tanguy wrote:
> 
> I'm looking for how to force the hor and ver refresh rates in Xorg. In
> xorg.conf ? Is there a gui tool for that like for choosing the screen
> resolution ?

First look under the gnome foot (left most icon on most desktops).

     Preferences --> screen resolution

Inspect the choices there and test.

Also look at xorg.conf and Xorgs log file.
     /etc/X11/xorg.conf
     /var/log/Xorg.0.log

Since 99% of the world is concerned with resolution and
color depth these parameters dominate all the tools.
I believe, that in the tools refresh rate is left unconstrained as an
unbounded degree of freedom to give the user more choices.

In /var/log/Xorg.0.log you might see messages like this:
    (**)...0): Validated modes for display device CRT-0:
    (**)...0):      Default mode "1280x1024": 157.5 MHz, 91.1 kHz, 85.0 Hz
    (**)...0):      Default mode "1024x768": 94.5 MHz, 68.7 kHz, 85.0 Hz

These validated modes tell you what is possible. These are the
computed values from the hardware driver and external (you provide)
info about the monitor.  You can dig into some additional xorg
documentation to specify which mode to load and how to specify it in
/etc/X11/xorg.conf multiple modes are possible.

Since video drivers are full of hardware specific stuff
you should tell us more about your specific hardware.

If I recall X will avoid 50 and 60 Hz because they do ugly things 
for some people under some lighting conditions.   
For most people X will just do the right thing.

You need to be more specific about what/why you want to change things.
Some caution If you "force the hor and ver refresh rates in Xorg." you
can damage hardware.  If your monitor is unknown to xorg and you have
the specifications you can add the hardware specifications to
/etc/X11/xorg.conf.  Looks sort of like this example:
 
   Section "Monitor"
        Identifier   "Monitor0"
        VendorName   "Monitor Vendor"
        ModelName    "Skinny Little Tube"
        HorizSync    30.0 - 96.0
        VertRefresh  48.0 - 160.0
        Option      "dpms"
    EndSection

As always be sure to update the xorg packages (yum or up2date).  Lots
of updates apply here...  Update first...

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