I don't why you'd want to browse the internet using MagiCMac on a Mac. Atari has shite for browsers. Sell your Mac and get a fast TOS clone. We have drivers for cheap generic network cards. For ADSL you will need a router/gateway of some sort that will do PPPoE but I hear that there might be PPPoE on the works for MiNT. Support the Atari community!! It might cost you more but that way we all get something out of it.
