Obtaining the Real to Protected Mode Switch Entry Point


                 This function  can be called in real mode to detect the
                 presence of DPMI services and to obtain an address that
                 can be used to begin execution in protected mode.

            To Call

                 AX = 1687h
                 Execute an Int 2Fh (not an Int 31h)

            Returns

                 If function was successful:
                 AX = 0
                 BX = Flags
                      Bit 0 = 1 if 32-bit programs are supported
                 CL = Processor type
                      02h = 80286
                      03h = 80386
                      04h = 80486
                 DH = DPMI major version number
                 DL = DPMI minor version number
                 SI =  Number  of  paragraphs  required  for  DPMI  host
                      private data (may be 0)
                 ES:DI = Address of procedure to call to enter protected
                      mode

                 If function was not successful:
                 AX != 0

            Programmer's Notes

                 o    This  function   does  not   perform  the   actual
                      transition into  protected mode.  You need to call
                      the address  returned in  ES:DI, after  allocating
                      the private  data  area  for  the  DPMI  host,  to
                      perform the actual real to protected mode switch.