AH = 58h
        AL = subfunction
            00h get mappable physical address array
               ES:DI = pointer to buffer to be filled with array
            01h get number of entries in m.p.a. array
Return: CX = number of entries in array
        AH = status
            00h successful
            80h internal error
            81h hardware failure
            84h undefined function requested
            8Fh undefined subfunction
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