A 32-bit MRCI client uses the sigOLD_EDX and sigNEW_EDX signature values to verify that an MRCI server has responded to the Detect MRCI Server (Interrupt 2Fh Function 04A12h) or Detect ROM BIOS MRCI Service (Interrupt 1Ah Function 0B001h) service. A 16-bit MRCI client uses the sigOLD_CX, sigNEW_CX, sigOLD_DX, and sigNEW_DX values.
Note that 32-bit MRCI clients must be virtual devices (VxDs). The Interrupt 2Fh interface is not directly callable from a Win32 application.