Configuring XFree86: A Step-By-Step Guide : Configuring the Monitor and its Modes
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## 5. Configuring the Monitor and its Modes

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.

Configuring XFree86: A Step-By-Step Guide : Configuring the Monitor and its Modes
Previous: Configuring the Video Hardware
Next: Combining the Video Hardware and Monitor Data