The AS/400 runs OS/400. It might use either a
proprietary processor
designed specifically for the AS/400, or it might use a special variant
of a PowerPC RISC. I don't know how to tell from the model number.
Likely an older one, as the new ones running the PowerAS chips are still
quite valuable (hell, they still make 'em!).
AS/400s are probably the best database boxes around, never break, never
crash, and have a bizzare CISC architecture that makes the VAX look like a
SPARC, but alas, are probably the most unhackable machines on the planet.
IBM made them to play by IBM's rules, and no one elses. Linux/400 is
unlikely, to say the least!
William Donzelli
william(a)ans.net