INT 67h,  59h  GET EXPANDED MEMORY HARDWARE INFORMATION              . 4.0

On entry:
        AH = 59h
        AL = subfunction
            00h get hardware configuration array
               ES:DI = pointer to buffer to be filled with array
            01h get unallocated raw page count

Return:
        BX = unallocated raw pages (subfunction 01h)
        DX = total raw pages (subfunction 01h)
        AH = status
            00h successful
            80h internal error
            81h hardware failure
            84h undefined function requested
            8Fh undefined subfunction
            A4h access denied by operating system

Note: subfunction 00h is for use by operating systems only, and can be
      enabled or disabled at any time by the operating system