INT 7F - Alloy NTNX (Host), MW386 - GET BUSY POINTER
        AH = 14h
        CL = 05h
        DX:DI -> buffer for busy structure (see below)
Return: DX:DI buffer filled

Format of busy structure:
Offset  Size    Description
 00h    DWORD   pointer to busy flag byte
 04h    WORD    fixed port address (FF00h)