Int 2F Fn FB43  PU - Borland Tdx - Installation Check                      [G]

   AX = FB43h
   BX = 0100h

Return: BX = FB43h if loaded
Program: TDX is Borland's Turbo Debugger variant for DPMI programs

Note:  Borland Pascal 7 DPMI programs use this call to check whether they
     should install their own stack and general protection exception
     handlers, or allow TDX to handle those exceptions