iSeries Model History
IBM renamed the AS400 platform iSeries in October 2000, as part of its e-business branding strategy. The iSeries model line ran through 2006, including a 2004 refresh onto POWER5 processors under the iSeries i5 name, before IBM renamed the platform again to System i.
IBM renamed the AS400 platform iSeries in October 2000, part of a company-wide push to attach the "e-business" and "eServer" branding to its server lines. The hardware and OS/400 software lineage continued forward without disruption; existing AS400 customers kept their applications and simply adopted new terminology and, over time, new hardware. The iSeries name lasted six years before IBM renamed the platform again to System i in 2006.
The iSeries Rename (2000)
IBM introduced the iSeries brand in October 2000 as part of the broader "eServer" family alongside the pSeries (UNIX), xSeries (x86), and zSeries (mainframe) lines. This was purely a branding change at launch: iSeries hardware in 2000 continued the same RISC, PowerPC-AS-derived architecture that AS400 had moved to in 1995, and ran the same OS/400 operating system. IBM marketed the rename under the "eServer iSeries" and, informally, "iSeries 400" names.
iSeries Model Line
The core iSeries model line spanned entry through high-end configurations, commonly referenced by model numbers including the iSeries 270 at the entry level, and the 810, 820, 825, 830, 840, 870, and 890 across midrange and high-end configurations. As with the AS400 generation before it, performance across this model range was rated using CPW, allowing IT teams to compare an older AS400 system's capacity against a target iSeries model when planning an upgrade.
The iSeries i5 Refresh (2004)
In 2004, IBM refreshed the iSeries line onto POWER5 processors, marketing the updated hardware as "iSeries i5" and rebranding the operating system from OS/400 to i5/OS at the same time. This refresh brought the platform onto the same POWER processor family used by IBM's UNIX (pSeries) systems, a step toward the hardware convergence that would culminate in the unified IBM Power Systems brand in 2008. The i5 naming carried forward into the System i era that followed.
From iSeries to System i
IBM retired the iSeries name in 2006, replacing it with System i as part of a company-wide unification of its server brands into System i, System p, System x, and System z. As with the 2000 rename, this was a branding change layered on top of continuously evolving hardware; the i5/OS operating system and application compatibility carried forward unchanged. See IBM Power Systems overview for how the naming resolved from there.