AH = 50h
        AL = subfunction
            00h
            01h
        DX = handle
        CX = number of entries in array
        DS:SI = pointer to mapping array
Return: AH = status
            00h successful
            80h internal error
            81h hardware malfunction
            83h invalid handle
            84h undefined function requested
            8Ah one or more logical pages are invalid
            8Bh one or more physical pages are invalid
            8Fh invalid subfunction
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