Int 2F Fn FA00  - Multiplex - ??? - Installation Check???                  [-]

   AX = FA00h
   BX = ??? (03FCh)
   CX = ??? (003Fh)
   DX = ??? (00FFh)
   SI = ??? (5AA6h)
   DI = ??? (0620h)

Return: ???

Note:  called by Matlab at startup