Internal CRT configuration

For internal CRT, you only need to confirm the CRT is configured to be the active display device. For example,

Section "Device"
       Driver   "via"
       VendorName  "VIA Tech"
       BoardName   "via"
       Identifier  "Device0"
       Option "ActiveDevice" "CRT"
       Screen 0 
EndSection    

External CRT configuration

For external CRT, besides configuring CRT to be the active display device, it's mandotary to set the digital port which external CRT uses. The external CRT could be connected through external transmitter, i.e. VT5907A.

You can use the following setting in the Section "Device" to set it.

Option "CRTPort" " DFP_HIGH" (or "DFP_LOW", "DFP_HIGHLOW" , "DVP0" , "DVP1")

DVP represents "Digital Visual Port".
DFP represents "Digital Flat Panel Port". They are all physical interfaces.
Each of DVP0 and DVP1 is a 12-bit digital port.
DFP is a 24-bit digitial port, but can be devided into two 12-bit digital ports, DFP_LOW and DFP_HIGH.

For example,

Section "Device"
       Driver   "via"
       VendorName  "VIA Tech"
       BoardName   "via"
       Identifier  "Device0"
       Option    "ActiveDevice" "CRT"
       Option     "CRTPort" "DFP_HIGH"
       Screen 0 
EndSection
  

Two CRTs configuration

To use both internal and external CRT, you should specify both CRT to be the active device, and the digital port which external CRT uses. For example,

Section "Device"
       Driver   "via"
       VendorName  "VIA Tech"
       BoardName   "via"
       Identifier  "Device0"
       Option "ActiveDevice" "CRT,CRT2"
       Option     "CRTPort" "DVP0 "
       Screen 0 
EndSection 

CRT Related Options

There are some specified options for CRT configuration. The options belong to the Section Device.

Option "Refresh" "integer"

This option set the refresh rate, which is the number of times in a second that display hardware draws the data it is being given. Increasing the refresh rate decreases flickering, thereby reducing eye strain. However, if a refresh rate is specified that is beyond what is recommended for the display, damage to the display can occur. For the supported resolution and refresh rate, you can get more information from Part III. Chapter 5. Depth and Resolution Configuration.