AS400 Learning Center
Foundational answers about the AS400 platform ... what it is, why it persists, and how it connects to modern IBM i and IBM Power systems.
The AS400 name has outlasted every official IBM rename. This section covers the fundamentals: what AS400 means, why organizations still run it, how the terminology evolved, and what the path forward looks like.
Articles in This Hub
AS400 History Timeline
This AS400 timeline tracks the platform from IBM's June 21, 1988 announcement through the 1995 RISC shift, the iSeries and System i rebrands, IBM i 7.5 and 7.6, and Power 5 through Power 11 milestone dates.
AS400 Login Explained
AS400 login usually means signing in to an IBM i user profile, most often through a 5250 green-screen session, IBM i Access Client Solutions, or a modern web interface tied to the same IBM i system.
AS400 Power Requirements
AS400 power requirements can mean either electrical requirements for the hardware or processing capacity requirements for the workload. The exact answer depends on whether you are discussing a legacy AS400 cabinet or a modern IBM Power replacement.
AS400 vs iSeries vs System i
AS400, iSeries, and System i are not separate product families. They are successive IBM brand names for the same platform lineage that now continues as IBM i on IBM Power Systems hardware.
Why Is It Still Called AS400?
AS400 remains the default name because it dominated the market for years, survived every IBM rebrand, and became the shorthand people still use for IBM i environments on IBM Power hardware.
AS400 vs IBM i
AS400 is a hardware brand name from 1988. IBM i is the current official name for the operating system that runs on IBM Power hardware. They are the same lineage, different names. Understanding the distinction matters for licensing, support conversations, and upgrade planning.
Is AS400 Still Used?
Yes. AS400 ... now called IBM i on IBM Power Systems ... is still actively used by thousands of organizations worldwide. IBM continues to invest in the platform with new hardware releases and OS updates.
What Is AS400?
AS400 is IBM's mid-range business computing platform introduced in 1988. Despite multiple name changes over the decades, AS400 remains the most widely used search term for IBM i, iSeries, and IBM Power systems worldwide.
What Replaced AS400?
IBM i on IBM Power Systems hardware replaced the AS400. The operating system evolved through iSeries, System i, and IBM i naming. IBM Power10 and Power11 are the current hardware generation. The workloads never disappeared ... only the brand names changed.