I am replacing an older HP 34401A DMM with an Agilent 34401A unit. The older HP unit works but the Agilent unit is causing an execption in the test software. The only difference that is noticeable between the 2 units is the I/O menu. The older unit has HP-IB / 488 as the interface while the newer unit interface is showing as GPIB / 488. The question is what is the difference?