Slight correction if I may Tmotten.
A Garmin does not need a computer. It functions as a standalone unit.
If you download osm maps ( on a separate App, I have virtually the whole world in the Navigator Android App and large amounts of old albeit still mostly the best available digitally for more remote areas. Soviet Military topo maps App.
you do need access to the web once to get them.)
It runs Android apps identical to those on your phone.
When it finds an open wifi network, it checks for app updates, Garmin app updates, checks weather forecasts, updates my currency app, checks email , skype etc etc ad nauseatum!!

If you own a Monterra, powered by Android, you have zero need for a computer.
It has wifi and bluetooth capability and self checks for any system updates just as any smartphone does.

SeoulJoe, this 'recalculating-recalculating' was back in 2000! Technology has hugely moved on ( and so should you!)

Have you thought about treating yourself to a Monterra? No need for speakers or an Ipod as the music stored on the Monterra plays back via small earphones. (tip: Bose noise cancelling ear phones are excellent!)
If you use turn-by-turn instructions, the Monterra can be set to either quieten or turn off the music when guiding instructions are spoken then resume playing the music.
And this satnav does so much more but it's not for the faint hearted!

(p.s rotten navigators always blame their satnav... )