INT 10 - VIDEO - Compaq SystemPro XL, LTE Lite - ???
        AX = BF0Fh
        BX = ??? or FFFFh to get current value
Return: CF clear
        AX = ???
Note:   this function calls AX=BF10h if BX=FFFFh and an EISA System ROM is
          present
SeeAlso: AX=BF10h

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