0040h:0063h           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:

                03B4h for Monochrome, or
                03D4h for Color Graphics Adapter