Int 21 Fn 251F  P - Phar Lap 386/dos-extender Vmm - Exhange Two Page-tabl  [E]

   AX = 251Fh
   BL = address type
       00h linear address
       ECX = linear address of first page table entry
       EDX = linear address of second page table entry
       01h pointer
       ES:ECX -> first page table entry
       ES:EDX -> second page table entry

Return: CF clear if successful
   CF set on error
       EAX = error code
       09h invalid address or NOPAGE option set
       82h not compatible with DPMI

See Also: AX=251Dh,AX=251Eh