Int 10h, 1003h          Select Intensity/Blink                       EGA, VGA

    Selects background intensity or blink attribute.

        Entry   AX = 1003h
                BL = 0 | 1   Background intensity | enable blinking

        Return  Nothing

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    Normally bit 7 of the attribute byte is used to indicate
    foreground blinking. With this service, bit 7 can indicate
    foreground blinking (BL = 1) or background intensity (BL = 0).