0:463h                   CRT Controller Base Address

 Length: 2 bytes

    Holds the CRT Controller Base Address. You can easily determine the
    current active display adapter by looking at this value. This base
    address is the video controller index register. This register is used
    to select which video controller register is to be accessed.


                 The value at this location is either:

                     3B4h for Monochrome, or
                     3D4h for Color Graphics Adapter