Int 2A Fn 0300  - Network (microsoft,lantastic) - Check Direct I/o         [N]

   AX = 0300h
   DS:SI -> ASCIZ device name (may be full path or only drive specifier--
       must include the colon)

Return: CF clear if direct physical addressing (INT 13,INT 25) permissible
   CF set if access via files only

Notes: do not use direct disk accesses if this function returns CF set or the
     device is redirected (INT 21/AX=5F02h)
   may take some time to execute
   this function is called by the DOS kernel on INT 25 and INT 26
   also supported by Lantastic, NetWare, 10NET, etc.

See Also: INT 13,INT 25,INT 26,INT 21/AX=5F02h