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The System i (formerly known as '''iSeries''', '''AS/400''', and '''Application System/400''') is a Minicomputer Platform produced by IBM . It was officially introduced in 1988 . It was then renamed to the eServer iSeries in 2000 as part of IBM's e-Server branding initiative. Now with the global move of the server and storage brands to the System brand with the Systems Agenda, the family has been renamed to '''System i''' in 2006 , with the POWER5 -based members of the series being called the '''System i5'''. MARKET POSITIONING As the current Midrange offering, the System i platform offers features intermediate between Mainframe Systems and PC -based servers. FEATURES The AS/400 platform extended the System/38 architecture of an object-based system with an integrated DB2 Database that was designed to implement E. F. Codd's Relational Database model, which is based on Codd's 12 Rules , in the Operating System and hardware. Equally important were the virtual machine and Single-level Storage concepts which established the platform as the most advanced business computer in the industry. Instruction set One feature that contributes to the longevity of the AS/400 and its successors is their high-level Instruction Set (called TIMI for "Technology Independent Machine Interface" by IBM), which allows Application Program s to take advantage of advances in hardware and software without recompilation. TIMI is a virtual instruction set; it is not the instruction set of the underlying CPU. User-mode programs contain both TIMI instructions and the machine instructions of the CPU, thus ensuring hardware independence. This is conceptually somewhat similar to the Virtual Machine architecture of programming environments such as Smalltalk , Java and .NET . The key difference is that it is embedded so deeply into the AS/400's design as to make applications effectively binary-compatible across different processor families. Note that, unlike some other virtual-machine architectures in which the virtual instructions are interpreted at Runtime , TIMI instructions are never interpreted. They constitute 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, in addition to the executable machine instructions. This is how application objects compiled on one processor family (e.g. the original CISC AS/400 48-bit processors) could be moved to a new processor (e.g. PowerPC 64-bit) without re-compilation. An application was saved from the older 48-bit platform and restored onto the new 64-bit platform where the operating system discarded the old machine instructions and re-translated the TIMI instructions into 64-bit instructions for the new processor. The AS/400's instruction set defines all pointers as 128-bit. This was an original design feature of the System/38 (S/38) in the mid 1970s. For PowerPC processors, the virtual address resides in the rightmost 64 bits of a pointer (48 bits in the S/38 and CISC AS/400), leaving room for addresses to be expanded past 64 bits in future processors. The 64-bit address space addresses all of main memory and disk (the single-level storage concept). The original AS/400 CISC models used the same 48-bit address space as the S/38. This was expanded to 64-bits in 1995 when the PowerPC RISC 64-bit CPU processor replaced the 48-bit CISC processor. I/O architecture An AS/400 system is actually an intelligent network of computers: database I/O is handled not by direct constant intervention of the CPU, but instead by processors dedicated to database and "channel" I/O. Likewise, the interactive terminal sessions are offloaded to a workstation processor. In this way, the apparently low-power/low clock-speed CPU is really not a limiting factor in the overall performance of the system - and performance can be modified to meet requirements: no terminal I/O processors and more disk subsystem for a dedicated web server, for example. Software is running natively on an iSeries Logical Partition.]] The AS/400 includes an extensive library-based Operating System , OS/400 , and is also capable of supporting multiple instances of AIX , Linux , Lotus Domino , Microsoft Windows 2000 and Windows Server 2003 . While OS/400, AIX, Linux and Lotus Domino are supported on the POWER processors, Windows is supported with either single-processor internal blade servers (IXS) or externally-linked multiple-processor servers (IXA). LPAR (Logical PARtitioning), a feature introduced from IBM's Mainframe computers, facilitates running multiple operating systems simultaneously on one AS/400 unit. A system setup with LPAR can even run different operating systems on different partitions while ensuring that one OS cannot run over the memory or resources of another. Each LPAR is given a portion of system resources (memory, hard disk space, and CPU time) via a system of weights that determines where unused resources are allocated at any given time. The operating systems supported (and commonly used) under the LPAR scheme are OS/400 , AIX , Linux and Lotus Domino . Other features include an integrated DB2 Database Management System , a menu-driven interface, Multi-user support, terminals ( IBM 5250 ) and printers, security, communications, client-server and web-based applications. All software necessary to run the AS/400 is included and integrated. More than 2,500 business software applications were available when the first AS/400 was delivered in 1988. Applications can run without modification on any model in the product line, from small, single-processor machines up to those with 64 multi-core CPUs and clustered systems. The later generations of the AS/400 - the iSeries and System i servers - also support common Client-server -based technologies such as ODBC and JDBC for accessing its database from client-based software, created with languages such as Java , Microsoft .NET languages and others. Unix98 applications can be implemented native on the i/OS platform without needing UNIX OS. Programming Programming languages available for the AS/400 include . Commands in the Control Language (CL) are promptable using the F4, and most provide cursor-sensitive help using the F1, to make entering parameters easier. A command name consists of a three-letter verb and a subject part, also referred to as a noun. Some command names provide a "modifier" as well. This is intended to make it easy to understand CL code. Examples:
For traditional business programming languages such as RPG, COBOL, C and SQL, the AS/400 has support for external files, display files and Object-oriented Programming , which allows for increased programming productivity. It also supports Unix and Windows stream files and directories, support for Java , Client-server technologies and a native Apache web server, for multi-tier applications. Integrated language environment Despite the lack of a Unix -like background, the AS/400 has, over the years, picked up the programming/runtime model found on Unix-like systems, Windows , OpenVMS , and many other operating systems. Traditional AS/400 programming is a "one-stop shop", where a programmer writes computer code, Compiles the code, and then executes the code. There is no link step that is found in other environments. However, in 1995 , that changed. IBM re-christened the one-stop shop programming style "OPM" (for Original Programming Model) and introduced a new language paradigm called "ILE" (for Integrated Language Environment). ILE had significant enhancements over OPM, including the ability to create modules (similar to .obj or .lib files), and then bind ( Link ) the modules together into a single executable. The executable could be created as a Program or a service program (service programs are similar to .lib or .dll files). The iSeries fully supports the Java language, including a 64-bit JVM that is implemented below the Operating System layer, closer to the hardware for superior performance. With i5/OS V5R4 there is now a 32-bit JVM that is also supported. HISTORY The AS/400 was the continuation of the , the operating system of the AS/400, did not have a UNIX background. Dr Frank Soltis , the chief architect, says that this is the main difference between this and any other operating system. The AS/400 was the first general-purpose computer system to attain a C2 security rating from the NSA , and in 1995 was extended to employ a 64-bit processor and operating system. In 2000 IBM renamed the AS/400 to iSeries, as part of its e-Server branding initiative. The product line was further extended in 2004 with the introduction of the i5 servers, the first to use the IBM POWER5 processor. The architecture of the system allows for future implementation of 128-bit processors when they become available. Existing applications can use the new hardware without modification. Although announced in 1988 , the AS/400 remains IBM's most recent major architectural shift that was developed wholly internally. Since the arrival of Lou Gerstner in 1993, IBM has viewed such colossal internal developments as too risky. Instead, IBM now prefers to make key product strides through acquisition -- e.g. the takeovers of Lotus Software and Rational Software -- and to support the development of open standards, particularly Linux. It is noteworthy that after the departure of CEO John Akers in 1993, when IBM looked likely to be split up, Bill Gates commented that the only part of IBM that Microsoft would be interested in was the AS/400 division. (At the time, many of Microsoft's internal systems ran on the AS/400 platform) 1 HARDWARE The AS/400 was originally based on a custom IBM CISC CPU which used a CPU architecture known as Internal MicroProgrammed Interface (IMPI) and an instruction set similar to the IBM 370 . It was later migrated to a POWER-based RISC CPU family eventually known as RS64 .2 CPU in AS/400, iSeries, i5 The System i5 uses IBM POWER CPUs. These CPUs are developed and manufactured by IBM. The POWER 4/5/5+ chips contain two cores. There are Multi-Chip Module s (MCM) available. They have 4 CPU (8 cores) or 8 CPUs (16 cores) in one MCM. Models of AS/400, iSeries, i5 systems SEE ALSO REFERENCES EXTERNAL LINKS
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