A most excellent series of computers produced by Atari during the 1980's. Featured a modified 6502 CPU with a special graphics CPU called the ANTIC, a true multi-cpu system on a single bus.
Had a truely device independent I/O system and linked files over 15 years before the evil empire ever thought of it.
Models included the 400, 800, 800XL, 600XL, 1200XL, 130XE, XEGS and others.