Configuring monitor modes can be a trying experience, unfortunately, because of the lack of standardization in monitor hardware. We have attempted to simplify this by collecting databases of specific monitor information, and assembling a set of "generic" modes that should get pretty much any monitor up and functional. For all the gory details of mode generation and tuning, refer to the `VideoModes.doc' document by Eric Raymond.
The monitor specs and video modes are described in the "Monitor"
sections in the XF86Config file. To create a Monitor section, you need
to know your monitor's specifications. In particular, you need to know
what range of horizontal sync and vertical sync (refresh) rates it supports and
what its video bandwidth is. This information should be available in
the monitor's user manual. Also check the 'Monitors' file to see if it
has an entry for your monitor. See the XF86Config(4/5)
manual page for details of how this information is entered into the
Monitor section.
Next, you need to provide a set of video modes that are suitable
for the monitor. The first step is to check in the 'Monitors' and
modeDB.txt files to see if there is a listing of modes for your
specific monitor. If there is, copy those modes to the Monitor section
of your XF86Config file. Verify that there is a clock listed on the
Clocks line in your XF86Config that matches the dot-clock in the 2nd
parameter of each mode line; delete any mode line that does not have a
matching clock on your card. If you still have modes left, you are in
good shape.
If you don't find any specific modes, or need more modes for the
resolutions you want to use, refer to the Generic Video Modes listing
below. Match the mode specification against your monitor's
specifications; pick the highest-refresh mode that is within specs, and
make sure you have a matching dot-clock on your Clocks line. Try the
VESA modes before any corresponding alternate mode setting. Copy the
mode specification to the Monitor section of your XF86Config
file.
Note that these modes are likely not optimal; they may not be sized
perfectly, or may not be correctly centered. But they should get you up
and running. If you want to tune the mode to your monitor, you can read
the 'Fixing Problems with the Image' section of the VideoModes.doc file.
A note before you are done. If the same mode name occurs more
than once in the Monitor section of the XF86Config file, the
server will use the first mode with a matching clock.
It is generally considered a bad idea to have more than one mode with
the same name in your XF86Config file.