The AS400 (Application System/400) is IBM's midrange business computing platform, introduced in 1988. It was renamed iSeries in 2000 and IBM i in 2008. It runs on IBM Power hardware and is known for exceptional reliability, security, and long application lifespan.

Is the AS400 still supported?

Yes. IBM i (the operating system formerly known as AS400/iSeries OS) is actively developed and supported by IBM. IBM i 7.5 is the current technology refresh. IBM Power 11 hardware fully supports IBM i workloads.

What replaced the AS400?

The AS400 was not replaced ... it evolved. AS400 became iSeries (2000), then IBM System i (2006), then IBM i running on IBM Power Systems (2008). The current equivalent runs on IBM Power 10 and Power 11 hardware with IBM i 7.5.

What Is an AS400? IBM's Midrange Platform Explained

The AS400 (Application System/400) is IBM's integrated midrange computing platform, first introduced on June 21, 1988. It was designed from the ground up as a business system combining hardware, operating system, database, and security into a single integrated platform.

The AS400 Name Evolution

The platform has gone through several name changes while remaining architecturally consistent:

AS400 ... Application System/400, 1988 to 2000
iSeries ... 2000 to 2006, introduced with POWER4-based hardware
IBM System i ... 2006 to 2008, briefly unified branding with other IBM Systems
IBM i on Power ... 2008 to present, IBM i operating system on Power Systems hardware

Why Organizations Still Run AS400 / IBM i

IBM i has an extraordinary track record for reliability and uptime. The platform is known for running business-critical applications ... ERP systems, order management, manufacturing control, financial systems ... for decades without interruption. Key reasons organizations maintain IBM i environments include:

Exceptional system availability (IBM i architecturally protects object integrity)
Integrated relational database (DB2 for i) built directly into the OS
Single-level storage architecture that simplifies application development
Decades of application investment that would be costly to replace
IBM i's security model is among the most comprehensive in the industry

The Current Platform: IBM i on IBM Power

Today, IBM i runs on IBM Power 10 and Power 11 hardware. IBM announced Power 11 on July 8, 2025, with new systems for IBM i, AIX, and Linux workloads. Organizations running AS400 workloads can migrate directly to Power 11 while preserving existing IBM i applications and data.