They have IRSs not INSs
Very simplified: you have IRS, GPS and then the conventional VHF/HF-systems all "reporting" to the FMC that tries to make out where the airplane is, displaying it on a map on the EFIS.
You also have the conventional presentation displayed via the EFIS or on the standby instrument, such as ILS, VOR, ADF.
The "ADIRU" collects information from the static/dynamic ports and the IRS to supply Heading, altitude, V/S, airspeed