Eirepreneur has more details about the Garmin/ GPS Ireland postcode system from a presentation given by Gary Delaney from GPS Ireland.
Eirepreneur says that Garmin Satnav will be creating its’ own system of Irish postcodes for ROI from the end of March on. You’ll be able to visit www.irishpostcodes.ie to get a code, and you can see more detail here. There are some sample codes up there- they will be 7 character (letter and number) geographically based codes.
Hopefully Google support will be added soon- we’d love for Jobyssey to have a location search feature (always important in Dublin), but without postcodes it was pretty much impossible to get a good result.