The IBM System i is a family of midrange computers from IBM. It was first introduced as the AS/400 (Application System/400) in June 1988, alongside the OS/400 operating system. It was intended as the successor to IBM's System/36 and System/38 platforms. Early AS/400 systems used the same IMPI architecture as the System/38, but later systems moved to the PowerPC-based IBM RS64.
It was re-branded multiple times by IBM: first as the AS/400 Advanced Series in 1994, followed by AS/400e (the "e" standing for e-business) in 1997, eServer iSeries in 2000, eServer i5 (along with OS/400 becoming i5/OS) in 2004, and finally System i in 2006.
In April 2008, System i and System p were consolidated into the IBM Power Systems platform. The i5/OS operating system was rebranded to IBM i, and retained full backwards compatibility with the previous hardware platforms.
Rebranding Timeline
- 1988 – AS/400 (Application System/400) launched
- 1994 – AS/400 Advanced Series
- 1997 – AS/400e (the "e" stands for e-business)
- 2000 – eServer iSeries
- 2004 – eServer i5 (OS/400 becomes i5/OS)
- 2006 – System i
- 2008 – Merged into IBM Power Systems (i5/OS becomes IBM i)
Summary
The predecessor to AS/400, IBM System/38, was first made available in August 1979 and was marketed as a minicomputer for general business and departmental use. It was sold alongside other product lines, each with a different architecture (System/3, System/32, System/34, System/36).
Realizing the importance of compatibility with the thousands of programs written in legacy code, IBM launched the AS/400 midrange computer line in 1988. "AS" stands for "Application System." Great effort was made during development of the AS/400 to enable programs written for the System/34 and System/36 to be moved to the AS/400. Programs on the System/38 were directly compatible with the new AS/400 after being "re-encapsulated" by the operating system.
In 2000, in accordance with IBM's eServer initiative, the AS/400 series was rebranded as the eServer iSeries. In 2006, it was again rebranded as the IBM System i. In 2008, almost 20 years after being introduced, the System i and IBM System p product lines were combined into the IBM Power Systems line.
The AS/400 operating system was originally named OS/400 (following the naming pattern begun with OS/360 and continued with OS/2). The operating system was renamed i5/OS to correspond with the introduction of POWER5 processors and the rebranding of the hardware to eServer iSeries. In 2008, it was renamed again to IBM i, alongside the introduction of IBM Power Systems.
The operating system is object-based. Features include a relational database management system (DB2/400), a menu-driven interface, support for multiple users, block-oriented terminal support (IBM 5250), and printers. IBM i has built-in security, and support for communications and web-based applications, which can run inside the optional IBM WebSphere Application Server or as PHP/MySQL applications inside a native port of the Apache web server.
Unlike the "everything is a file" model of Unix and its derivatives, on IBM i everything is an object, with built-in persistence and garbage collection. IBM i also offers Unix-like file directories through the Integrated File System. Java compatibility is implemented through a native port of the Java virtual machine.
Like IBM's mainframe operating systems, IBM i uses EBCDIC as its inherent encoding.
OS/400 Version 4, Release 4 (V4R4) introduced LPARs (logical partitions), allowing multiple virtual systems to run on a single hardware footprint.
Features
The IBM System i platform extended the System/38 architecture of an object-based system with an integrated DB2 relational database. Equally important are the virtual machine and single-level storage concepts which established the platform as an advanced business computer.
Instruction Set
One feature that has contributed to the longevity of the IBM System i platform is its high-level instruction set, known as TIMI (Technology Independent Machine Interface), which allows application programs to take advantage of advances in hardware and software without recompilation. TIMI is a virtual instruction set independent of the underlying machine instruction set of the CPU. User-mode programs contain both TIMI instructions and the machine instructions of the CPU, ensuring hardware independence — conceptually similar to the virtual machine architecture of environments such as Java and .NET.
Unlike other virtual-machine architectures where virtual instructions are interpreted at run time, TIMI instructions are never interpreted. They form an intermediate compile-time step and are translated into the processor's instruction set as the final compilation step. The TIMI instructions are stored within the final program object alongside the executable machine instructions. This is how application objects compiled on one processor family (for example, the original CISC AS/400 48-bit processors) could be moved to a new processor family (such as 64-bit PowerPC) without recompilation. An application saved from the older 48-bit platform can simply be restored onto the new 64-bit platform, where the operating system discards the old machine instructions and re-translates the TIMI instructions for the new processor.
The system's instruction set defines all pointers as 128-bit. This was an original design feature of the System/38 in the mid-1970s, planned for future processors, memory, and expanded address space. The original AS/400 CISC models used the same 48-bit address space as the System/38. That address space was expanded in 1995 when the RISC PowerPC RS64 64-bit CPU replaced the 48-bit CISC processor.
For 64-bit PowerPC processors, the virtual address resides in the rightmost 64 bits of a pointer, versus 48 bits on the System/38 and CISC AS/400. The 64-bit address space references main memory and disk as a single address set — the single-level storage concept.
Software
The IBM System i includes an operating system originally known as OS/400, later renamed i5/OS and then IBM i. System i is also capable of supporting multiple instances of AIX, Linux, Lotus Domino, and Microsoft Windows. While OS/400, AIX, Linux, and Lotus Domino run on POWER processors, Windows is supported through single-processor internal blade servers or externally linked multiple-processor servers. Windows, Linux, and VMware ESX are supported on iSCSI-attached servers.
LPAR (Logical Partitioning), a feature introduced from IBM's mainframe computers, allows multiple operating systems to run simultaneously on one IBM System i unit. A system configured with LPAR can run various operating systems on separate partitions while ensuring that one OS cannot consume the memory or resources of another. Each LPAR is given a portion of system resources (memory, hard disk space, and CPU time) through a system of weights that determines how unused resources are allocated. The operating systems commonly used under the LPAR scheme are IBM i, AIX, and Linux.
Other features include an integrated DB2 database management system, a menu-driven interface, multi-user support, non-programmable terminals (IBM 5250) and printers, security, communications, and client–server and web-based applications. Much of the software necessary to run IBM System i is included and integrated into the base operating system.
IBM System i also supports common client–server standards such as ODBC and JDBC for accessing its database from client software such as Java, Microsoft .NET languages, and others.
History
The IBM System i, then known as the AS/400, was the continuation of the System/38 database machine architecture, announced by IBM in October 1978 and delivered in August 1979. The AS/400 removed capability-based addressing and added source compatibility with the System/36, combining the two primary computers manufactured by the IBM Rochester plant. The System/36 was IBM's most successful minicomputer, but the architecture had reached its limit.
The first AS/400 systems (development code names "Silverlake," named for Silver Lake in downtown Rochester, Minnesota, where development took place, and "Olympic") were delivered in 1988 under the tagline "Best of Both Worlds," and the product line has been refreshed continually since. The programmers who worked on OS/400 did not have a Unix background; chief architect Dr. Frank Soltis noted this as a key difference between OS/400 and other operating systems of its era.
The AS/400 was one of the first general-purpose computer systems to attain a C2 security rating from the NSA, and in 1995 it was extended to employ a 64-bit processor and operating system.
The 1995 change-over from IMPI (48-bit addresses) to PowerAS (64-bit addresses) required that all programs be "observable," meaning the debugging information had not been stripped from the compiled code. This caused problems for customers who had bought third-party products with no source and no observability. In 2008, the release of i5/OS V6R1 (later IBM i 6.1) caused similar issues due to changes to the TIMI in that release.
In 2000, IBM renamed the AS/400 to iSeries as part of its eServer branding initiative. At that time it adopted more PC-server-like features, such as standard keyboards, mice, and VGA video output, replacing older proprietary technologies. In 2001, it switched to the POWER4 processor from the PowerAS processors used by previous generations.
The product line was extended further in 2004 with the introduction of the i5 servers, the first to use the IBM POWER5 processor. The architecture was designed to allow for future 128-bit processors as they become available.
Although announced in 1988, the AS/400 remains one of IBM's most significant architectures developed wholly in-house. Since the early 1990s, IBM has generally grown its product lines through acquisition and the adoption of open standards such as Linux rather than large internal platform development. The AS/400 was widely regarded as one of IBM's most valuable and defensible product lines through the 1990s; Microsoft itself ran many of its own business and financial systems on the AS/400 platform until around 1999, when it transitioned to Windows 2000.
Hardware
The AS/400 was originally based on a custom IBM CISC CPU with an instruction set architecture known as IMPI (Internal Microprogrammed Interface), similar to that of the IBM System/370. It was later migrated to a POWER-based RISC CPU family, eventually known as RS64.
CPU Generations
The System i5 used POWER CPUs, developed and manufactured by IBM. The POWER4, POWER5, and POWER5+ chips contain two cores. Multi-Chip Modules (MCM) are available with two CPUs (four cores) or four CPUs (eight cores) per module.
| CPU | Year | Clock Speed | Platform | Server Models |
|---|---|---|---|---|
| IMPI | 1988 | > 22 MHz | AS/400 | Bxx, Cxx, Dxx, Exx, Fxx, Pxx, 100, 135, 140, 2xx, 3xx |
| Cobra (A10) | 1995 | 55 or 75 MHz | AS/400 | 4xx, 5xx |
| Muskie (A25/A30) | 1996 | 125 or 154 MHz | AS/400 | 53x |
| Apache / RS64 (A35) | 1997 | 125 MHz | AS/400 | 6xx, 150 |
| NorthStar (RS64 II) | 1998 | 200, 255 or 262 MHz | AS/400 | 170, 250, 7xx, 650, S40, SB1 |
| Pulsar (RS64 III) | 1999 | 450 MHz | iSeries / System i | 270, 820 |
| IStar (RS64 III upgraded) | 2000 | 400, 500, 540 or 600 MHz | iSeries / System i | 820, 830, 840, SB2, SB3 |
| SStar (RS64 IV) | 2000 | 540, 600 or 750 MHz | iSeries / System i | 270, 800, 810, 820, 830, 840 |
| POWER4 | 2001 | 1.1 or 1.3 GHz | iSeries / System i | 890 |
| POWER4+ | 2003 | 1.9 GHz | iSeries / System i | 825, 870 |
| POWER5 | 2004 | 1.5 or 1.9 GHz | iSeries / System i | i5-520, i5-550, i5-570, i5-595 |
| POWER5+ | 2005 | 1.5–2.3 GHz | iSeries / System i | i5-520, i5-550, i5-515, i5-525, i5-570 |
| POWER6 | 2007 | 3.5–4.7 GHz | iSeries / System i | BladeCenter JS12, JS22; i5-570 (MMA); M50, M25, M15 |
| POWER6+ | since 2009 | 3.6–5.0 GHz | iSeries / System i | BladeCenter JS12, JS22, JS23, JS43; Power 520, 550, 560, 570, 575, 595 |
| POWER7 | 2010 | 3.3–4.2 GHz | Power Systems | BladeCenter PS700, PS701, PS702; PureSystems p260, p460, p24L; PowerLinux 7R1, 7R2; Power 710–795 |
| POWER7+ | 2012 | 3.7–4.4 GHz | Power Systems | BladeCenter PS703, PS704; PureSystems p260, p460, p24L; PowerLinux 7R1, 7R2; Power 710–795 |
| POWER8 | 2014 | 2.5–5.0 GHz | Power Systems | Power S812L, S814, S822, S822L, S824, S824L, S812LC, S821LC, S822LC; Power E850, E870, E880 |
| POWER9 | 2017 | 4 GHz | Power Systems | Power AC922, L922, S914, S922, S924, H922, H924, E950, E980 |
| POWER10 | 2021 | 3.5–4.0 GHz | Power Systems | S1012, S1014, S1022, S1022s, S1024, E1050, E1080 |
| POWER11 | 2025 | 3.0–4.4 GHz | Power Systems | S1112, S1122, S1124, E1150, E1180 |
Note: there were at least two generations of IMPI processors; the second was released in 1991, with a processor clock cycle of 45 ns worst case.
Server Models
| Model | Year | CPU Group | Base CPW |
|---|---|---|---|
| B10, B20, B30, B35, B40, B45, B50, B60, B70 | 1988, 1989 | P10, P20 | 2.9 – 20 |
| C04, C06, C10, C20, C25 | 1990 | P10 | 3.1 – 6.1 |
| D02, D04, D06, D10, D20, D25, D35, D45, D50, D60, D70, D80 | 1991 | P10, P20, P30 | 3.8 – 56.6 |
| E02, E04, E06, E10, E20, E25, E35, E45, E50, E60, E70, E80, E90, E95 | 1992 | P10, P20, P30, P40 | 4.5 – 116.6 |
| F02, F04, F06, F10, F20, F25, F35, F45, F50, F60, F70, F80, F90, F95, F97 | 1993 | P05, P10, P20, P30, P40 | 5.5 – 177.4 |
| P01, P02, P03 | 1993–1995 | P05 | 7.3 – 16.8 |
| 150 | 1996 | P05 | 10.9 – 35.0 |
| S10, S20, S30, S40 | 1997 | P05, P10, P20, P30, P40, P50 | 45.4 – 4550 |
| SB1, SB2, SB3 | 1997, 2000 | P30, P40 | 1794 – 16500 |
| 10S, 100, 135, 140 | 1993–1995 | P05, P10, P20 | 17.1 – 65.6 |
| 170 | 1998 | P05, P10, P20 | 30 – 1090 |
| 200, 20S, 236 | 1994 | P05, P10 | 7.3 – 17.1 |
| 250 | 2000 | P05 | 50 – 75 |
| 270 | 2000 | P05, P10, P20 | 50 – 2350 |
| 300, 30S, 310 | 1994 | P10, P20, P30, P40 | 11.6 – 177.4 |
| 400, 40S, 436 | 1995 | P05, P10 | 13.8 – 91.0 |
| 500, 50S, 510, 530, 53S | 1995 | P10, P20, P30, P40 | 18.7 – 650 |
| 600, 620, 640, 650 | 1997 | P05, P10, P20, P30, P40, P50 | 22.7 – 4550 |
| 720 | 1999 | P10, P20, P30 | 240 – 1600 |
| 730 | 1999 | P20, P30, P40 | 560 – 2890 |
| 740 | 1999 | P40, P50 | 3660 – 4550 |
| 800 | 2003 | P05, P10 | 300 – 950 |
| 810 | 2003 | P10, P20 | 750 – 2700 |
| 820 | 2000, 2001 | P05, P10, P20, P30, P40 | 100 – 3700 |
| 825 | 2003 | P30 | 3600 – 6600 |
| 830 | 2000, 2002 | P20, P30, P40, P50 | 1850 – 7350 |
| 840 | 2000–2002 | P40, P50 | 10000 – 20200 |
| 870 | 2002 | P40, P50 | 7700 – 20000 |
| 890 | 2002 | P50, P60 | 20000 – 37400 |
| 520 | 2004–2006 | P05, P10, P20 | 500 – 7100 |
| 550 | 2004–2006 | P20 | 3300 – 14000 |
| 570 | 2004–2006 | P30, P40 | 3300 – 58500 |
| 595 | 2004–2006 | P50, P60 | 24500 – 216000 |
| 515 | 2007 | P05 | 3800 – 7100 |
| 525 | 2007 | P10 | 3800 – 7100 |
| 570 | 2007 | P40 | 16700 – 58500 |
| MMA (9406) | 2007 | P30 | 5500 – 76900 |
| M15 | 2008 | P05 | 4300 |
| M25 | 2008 | P10 | 4300 – 8300 |
| M50 | 2008 | P20 | 4800 – 18000 |
| MMA | 2008 | P30 | 8150 – 76900 |
| JS12 | 2008 | P05 | 7100 |
| JS22 | 2008 | P10 | 13800 |
| JS23 | 2008 | – | – |
| JS43 | 2008 | – | – |
| 570 (9117) | 2008 | P30 | 104800 |
| 595 (9119) | 2008 | P60 | 294700 |
Current Power Systems Models (Power9 – Power11)
IBM stopped publishing a single comparable Base CPW figure once Power Systems began running AIX, IBM i, and Linux side by side on the same hardware, so the table below picks up where the legacy CPW table leaves off, tracking model, machine type, and core/memory capacity through the current Power11 generation. Model names link to full specifications and pricing on Midland Information Systems.
| Model | Machine Type | Year | Sockets / Cores | Max Memory |
|---|---|---|---|---|
| Power9 | ||||
| S914 | 9009-41G | 2018 | 1 socket, up to 8 cores | up to 1 TB |
| S922 | 9009-22G | 2018 | 2 sockets, up to 20 cores | up to 4 TB |
| S924 | 9009-42G | 2018 | 2 sockets, up to 24 cores | up to 4 TB |
| H922 | 9223-22H | 2018 | 2 sockets, up to 20 cores | up to 4 TB |
| H924 | 9223-42H | 2018 | 2 sockets, up to 24 cores | up to 4 TB |
| E950 | 9040-MR9 | 2018 | 4 sockets, up to 48 cores | up to 16 TB |
| E980 | 9080-M9S | 2018 | up to 16 sockets, up to 192 cores | up to 64 TB |
| Power10 | ||||
| S1012 | 9028-21B | 2022 | 1 socket, up to 8 cores | up to 256 GB |
| S1014 | 9105-41B | 2021 | 1 socket, up to 8 cores | up to 1 TB |
| S1022s | 9105-22B | 2021 | 2 sockets, up to 16 cores | up to 2 TB |
| S1022 | 9105-22A | 2021 | 2 sockets, up to 40 cores | up to 4 TB |
| S1024 | 9105-42A | 2021 | 2 sockets, up to 48 cores | up to 8 TB |
| E1050 | 9043-MRX | 2022 | 4 sockets, up to 96 cores | up to 16 TB |
| E1080 | 9080-HEX | 2021 | up to 16 sockets, up to 240 cores | up to 34 TB |
| Power 11 | ||||
| S1112 | 9242-21B | 2025 | 1 socket, up to 10 cores | – |
| S1122 | 9824-22A | 2025 | 2 sockets, up to 60 cores | up to 4 TB |
| S1124 | 9824-42A | 2025 | 2 sockets, up to 60 cores | up to 8 TB |
| E1150 | 9043-MRU | 2025 | 4 sockets, up to 120 cores | up to 16 TB |
| E1180 | 9080-HEU | 2025 | up to 8 sockets, up to 120 cores per node (256 cores max, multi-node) | up to 16 TB per node (64 TB max, multi-node) |