Pantload, no, if that's how I sounded I apologize, I don't pretend to know the inner workings of the ADIRU's as much as I'd like to, it just happened to be a question that came up last week, one of my new era FO's who knows the SOP backward and forward, pulling down the compass bla bla bla did a wonderful cockpit setup in my absence and one of the first things I did was to look at the position monitor, all IR's had over a three mile error, I thought to myself that it was an error by the other pilot but then asked myself, what is the harm, as soon as the thrust levers are pushed forward everything will be fine, (15 year old A320 no GPS) operating in class one NAV, not over water. Any further comment appreciated.