System i
IBM's server product line running i5/OS (later IBM i), the direct descendant of the AS/400, sold as a separate brand from System p until the 2008 Power Systems unification.
System i was IBM's product name, used from roughly 2004 through early 2008, for the server line descended from the AS/400, running i5/OS on POWER5 and early POWER6 hardware. It was marketed separately from System p even though both shared silicon.
Related Terms
Power Systems
The unified IBM server brand created in April 2008 when System i and System p, previously separate product lines, merged on the POWER6 processor generation.
System p
IBM's AIX/Linux-focused server product line, sold on the same underlying POWER processor family as System i but as a separate brand until the 2008 Power Systems unification.
IBM i
The current name of the operating system that ran the AS/400 as OS/400 and later i5/OS. Renamed to IBM i in April 2008, alongside the Power Systems brand unification.
i5/OS
The name used for the AS/400's operating system from 2004 to 2008, between OS/400 and IBM i, tied to the POWER5 processor generation it launched alongside.