Editing IBM AS/400 (section)

== History ==

=== Fort Knox ===
[[File:IBM AS-400 9404-B10.jpg|thumb|right|upright|IBM AS/400 9404-B10 with a [[IBM 5250|5281]] terminal]]
In the early 1980s, IBM management became concerned that IBM's large number of incompatible [[midrange computer]] systems was hurting the company's competitiveness, particularly against [[Digital Equipment Corporation]]'s [[VAX]].<ref>{{cite book|title=The Silverlake Project: Transformation at IBM|author1=Roy A. Bauer|author2=Emilio Collar|author3=Victor Tang|year=1992|publisher=Oxford University Press|isbn=9780195067545}}</ref> In 1982, a project named ''Fort Knox'' commenced, which was intended to consolidate the [[System/36]], the [[System/38]], the [[IBM 8100]], the [[Series/1]] and the [[IBM 4300]] series into a single product line based around an [[IBM 801]]-based processor codenamed ''Iliad'', while retaining backwards compatibility with all the systems it was intended to replace.{{sfnp|Soltis|1997|p={{pn|date=March 2022}}}} A new operating system would be created for Fort Knox, but the operating systems of each platform which Fort Knox was intended to replace would also be ported to the Iliad processor to allow customers to migrate their software to the new platform.

The Fort Knox project proved to be overly ambitious and ran into multiple delays and changes of scope. As the project advanced, the requirement to support IBM 8100 and Series/1 software was dropped.<ref name="schleicher-interview" /> When IBM's engineers attempted to port the operating systems and software of their existing platforms, they discovered that it would be impossible without making extensive changes to the Iliad processor for each individual operating system — changes that Iliad's architects were unwilling to make.{{sfnp|Soltis|1997|p={{pn|date=March 2022}}}} The proposed solution to this was to augment Iliad with operating system-specific co-processors that provided hardware support for a single operating system. However, the amount of logic needed in each co-processor grew until the co-processors became the main processor, and the Iliad was relegated to the role of a support processor — thus failing the goal of consolidating on a single processor architecture. The Fort Knox project was ultimately cancelled in 1985.

[[File:IBM AS-400 9406-720.jpg|thumb|right|IBM AS/400]]
[[Image:IBM eServer i5 570.jpg|thumb|right|IBM System i 570 server (as of 2006).]]

=== Silverlake ===
During the Fort Knox project, a [[skunkworks project]] was started at [[IBM Rochester]] by engineers who believed that Fort Knox's failure was inevitable. These engineers developed code that allowed System/36 applications to run on top of the System/38,<ref name="schleicher-interview" /> and when Fort Knox was cancelled, this skunkworks project evolved into an official project to replace both the System/36 and System/38 with a single new hardware platform.{{sfnp|Soltis|2001|p={{pn|date=October 2023}}}} The project became known as ''Silverlake'' (named for [[Silver Lake (Rochester, Minnesota)|Silver Lake in Rochester, Minnesota]]) and officially began in December 1985.<ref>{{cite web|website=helpsystems.com |url=https://www.helpsystems.com/blog/happy-30th-anniversary-ibm-i|title=Happy 30th Anniversary, IBM i! |author=Tom Huntington|date=2018-06-21 |access-date=2021-03-05|archive-date=2021-04-20 |archive-url=https://web.archive.org/web/20210420033243/https://www.helpsystems.com/blog/happy-30th-anniversary-ibm-i|url-status=dead}}</ref> The Silverlake hardware was essentially an evolution of the System/38 that reused some of the technology developed for the Fort Knox project.<ref name="schleicher-interview"/><ref>{{cite web|url=https://wiki.midrange.com/index.php/Silverlake |title=Silverlake |website=wiki.midrange.com |date=2006-08-21|access-date=2021-03-06}}</ref>

Silverlake's goal was to deliver a replacement for the System/36 and System/38 in as short a timeframe as possible, as the Fort Knox project had stalled new product development at Rochester, leaving IBM without a competitive midrange system.<ref name="brave-new-world">{{cite web |url=https://www.postbulletin.com/the-brave-new-world-of-ibm-rochester-by-eric-j/article_dca93382-06b2-5f8a-8c4a-a42b58334432.html|title=The brave new world of IBM Rochester |author=Eric J. Wieffering |date=1992-05-23|website=postbulletin.com|access-date=2021-03-06}}</ref> On its launch in 1986, the System/370-compatible [[IBM 9370]] was positioned as IBM's preferred midrange platform, but failed to achieve the commercial success IBM hoped it would have.{{sfnp|Soltis|1997|p={{pn|date=March 2022}}}}<ref>{{cite news |url=https://www.chicagotribune.com/news/ct-xpm-1988-06-20-8801090224-story.html|title=NEW IBM MIDRANGE TO DEBUT |author=Christine Winter |date=1988-06-20|newspaper=[[Chicago Tribune]]}}</ref> Much like Silverlake, the 9370 also reused the co-processor developed during the Fort Knox project as its main processor and the same SPD I/O bus that was derived from the [[Series/1]] bus.{{sfnp|Soltis|1997|p={{pn|date=March 2022}}}}

=== AS/400 ===
On June 21, 1988, IBM officially announced the Silverlake system as the ''Application System/400'' (AS/400). The announcement included more than 1,000 software packages written for it by IBM and IBM Business Partners.<ref>{{cite web |last1=IBM |title=IBM AS/400 |url=https://www.ibm.com/ibm/history/exhibits/rochester/rochester_4010.html |website=IBM |date=23 January 2003 |publisher=International Business Machines Corporation |access-date=19 March 2022}}</ref> The AS/400 operating system was named ''Operating System/400'' (OS/400).<ref name="schleicher-interview">{{cite interview |last=Schleicher|first=David L.|date=2006-01-24 |interviewer=Arthur L. Norberg |url=https://conservancy.umn.edu/bitstream/handle/11299/107623/oh381ds.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://conservancy.umn.edu/bitstream/handle/11299/107623/oh381ds.pdf |archive-date=2022-10-09 |url-status=live|publisher=Charles Babbage Institute |title=An Interview with DAVID L. SCHLEICHER |website=conservancy.umn.edu|access-date=2021-03-05}}</ref>

The creators of the AS/400 originally planned to use the name ''System/40'', but IBM had adopted a new product nomenclature around the same time, which led to the Application System/400 name.{{sfnp|Soltis|2001|p={{pn|date=October 2023}}}}  First, IBM began prefixing "System" in product names with words to indicate the intended use or target market of the system (e.g., [[Personal System/2]] and [[Enterprise System/9000]]). Second, IBM decided to reserve one- and two-digit model numbers for personal systems (e.g., [[PS/2]] and [[PS/55]]), three-digit numbers for midrange systems (e.g., AS/400) and four-digit numbers for mainframes (e.g., [[ES/9000]]). The reassignment of two-digit model numbers from midrange systems to personal systems was to prevent the personal systems from running out of single-digit numbers for new products.

=== The move to PowerPC ===
{{See also|IBM RS64#History}}

In 1990, IBM Rochester began work to replace the AS/400's original System/38-derived [[48-bit computing|48-bit]] [[complex instruction set computer|CISC]] processors with a 96-bit architecture known as ''C-RISC'' (Commercial [[RISC]]).{{sfnp|Soltis|1997|p={{pn|date=March 2022}}}} Rather than being a clean-slate design, C-RISC would have added RISC-style and [[VLIW]]-style instructions to the AS/400's processor, while maintaining backwards compatibility with the [[System/370]]-style ''Internal Microprogrammed Interface'' (IMPI) instruction set and the [[microcode]] used to implement it.

In 1991, at the request of IBM president [[Jack Kuehler]], a team under the leadership of [[Frank Soltis]] delivered a proposal to adapt the [[64-bit computing|64-bit]] [[PowerPC]] architecture to support the needs of the AS/400 platform.<ref>{{cite book|author1=John Paul Shen|author2=Mikko H. Lipasti|title=Modern Processor Design: Fundamentals of Superscalar Processors|url=https://books.google.com/books?id=ffQqAAAAQBAJ|date=30 July 2013|publisher=Waveland Press |isbn=978-1-4786-1076-2}}</ref> Their extensions to the PowerPC architecture, known as ''Amazon'' (and later as ''PowerPC AS''), were approved by IBM management instead of the C-RISC design for development into the next AS/400 processor architecture.<ref>{{cite magazine|title=Inside the PowerPC AS |url=http://iprodeveloper.com/systems-management/inside-powerpc |date=July 1, 1995 |author1=Adam T. Stallman|author2=Frank G. Soltis |magazine=System iNEWS Magazine|archive-url=https://web.archive.org/web/20130831203807/http://iprodeveloper.com/systems-management/inside-powerpc |archive-date=August 31, 2013}}</ref> These extensions include support for tagged memory,<ref>{{cite web |last=Landau |first=Hugo |url=https://www.devever.net/~hl/ppcas|title=The PowerPC AS Tagged Memory Extensions}}</ref> as well as assistance for decimal arithmetic.<ref>{{cite newsgroup|last=McKenzie |first=Dave |url=https://groups.google.com/g/comp.arch/c/TgbBBxCdK0E/m/HlmFfkymuPcJ|title=Re: Packed decimals |date=December 5, 2000|message-id=fopr2tg596q0s28ibma1bkj05skcdldct8@4ax.com |newsgroup=comp.arch}}</ref>

IBM initially attempted to create a single PowerPC implementation for both AS/400 and high-end RS/6000 systems known as ''Belatrix''.{{sfnp|Soltis|1997|p={{pn|date=March 2022}}}} The Belatrix project proved to be too ambitious, and was cancelled when it became apparent that it would not deliver on schedule. Instead, a pair of AS/400-specific processors were designed at IBM Endicott and IBM Rochester, known as ''Cobra'' (for low end systems) and ''Muskie'' (for high end systems) respectively. These became the initial implementations of the [[IBM RS64]] processor line. The RS64 series continued to be developed as a separate product line at IBM until the [[POWER4]] merged both the RS64 and POWER product lines together.{{sfnp|Soltis|2001|p={{pn|date=October 2023}}}}

Despite the move from IMPI to an entirely different processor architecture, the AS/400's [[IBM i#TIMI|Technology Independent Machine Interface]] (TIMI) mostly hid the changes from users and applications, and transparently recompiled applications for the new processor architecture.<ref name="as400-technical-introduction" /> The port of OS/400 to the PowerPC AS architecture required a rewrite of most of the code below the TIMI due to the use of IMPI microcode to implement significant quantities of the operating system's low level code.{{sfnp|Soltis|2001|p={{pn|date=October 2023}}}} This led to the creation of the System Licensed Internal Code (SLIC) - a new implementation of the lower levels of the operating system mostly written in [[C++]].

=== Rebranding ===
The AS/400 family line was rebranded several times in the 1990s and 2000s as IBM introduced newer generations of hardware and operating system.<ref name="as400-technical-introduction">{{cite web |author=Tom Van Looy|date=January 2009 |title=The IBM AS/400: A technical introduction |website=scss.tcd.ie |url=https://www.scss.tcd.ie/SCSSTreasuresCatalog/hardware/TCD-SCSS-T.20121208.068/IBM-AS400-technical-introduction.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.scss.tcd.ie/SCSSTreasuresCatalog/hardware/TCD-SCSS-T.20121208.068/IBM-AS400-technical-introduction.pdf |archive-date=2022-10-09 |url-status=live |access-date=2021-03-13}}</ref> 

In 1994, the ''AS/400 Advanced Series'' name was used for new models, followed by the rebranding of the product line to ''AS/400e'' (the ''e'' standing for [[Online business|e-business]]) in 1997.{{sfnp|Soltis|2001|p={{pn|date=October 2023}}}}

In 2000, the ''eServer iSeries'' was introduced as part of its ''[[IBM eServer|eServer]] branding initiative''.<ref>{{cite web|title=IBM eServer iSeries 400|url=https://www-01.ibm.com/common/ssi/rep_ca/9/897/ENUS100-309/index.html|date=October 3, 2000|publisher=IBM}}</ref> The eServer iSeries was built on the [[POWER4]] processor from the RS64 processors used by previous generations, meaning that the same processors were used in both the iSeries and [[pSeries]] platforms, the latter of which ran [[AIX]].

In 2004, ''eServer i5'' (along with OS/400 becoming ''i5/OS'') the ''5'' signifying the use of [[POWER5]] processors, was introduced, replacing the eServer iSeries brand.<ref>{{cite web|author=Denny Insell |url=https://www.gateway400.org/documents/Gateway400/Handouts/2004%20IBM%20eServer%20i5%20Exec%20Overview%2009-09-2004%20St%20Louis%20MOL.pdf |url-status=live |access-date=2021-03-14 |archive-url=https://ghostarchive.org/archive/20221009/https://www.gateway400.org/documents/Gateway400/Handouts/2004%20IBM%20eServer%20i5%20Exec%20Overview%2009-09-2004%20St%20Louis%20MOL.pdf |archive-date=2022-10-09 |title=Introducing IBM eServer i5 & i5/OS|publisher=IBM|date=2004}}</ref>  Successive generations of iSeries and pSeries hardware converged until they were essentially the same hardware sold under different names and with different operating systems.<ref name="system-p-i" /> Some i5 servers were still using the AS/400-specific IBM Machine Type (MT/M 9406-520) and were able to run AIX in a [[logical partition]] along i5/OS, while the p5 servers were able to run i5/OS, respectively. The licensing for AIX and i5/OS was controlled in the firmware by the POWER hypervisor.

The final rebranding occurred in 2006, when IBM rebranded the eServer i5 to ''System i''.<ref>{{cite web |author=Alex Woodie|date=2017-10-11 |url=https://www.itjungle.com/2017/10/11/ibm-slow-catch-mean/ |title=IBM i Slow to Catch On, But What Does It Mean?|access-date=2021-03-15 |website=itjungle.com}}</ref>

In April 2008, IBM introduced the [[IBM Power Systems]] line, which was a convergence of System i and System p product lines.<ref name="Niccolai"/> The first Power Systems machines used the [[POWER6]] processors; i5/OS was renamed as ''IBM i'' in order to remove the association with POWER5 processors.<ref>{{cite web|title=IBM Introduces the First in a New Generation of Power Systems|url=https://www-03.ibm.com/press/us/en/pressrelease/23795.wss |archive-url=https://web.archive.org/web/20080511231914/http://www-03.ibm.com/press/us/en/pressrelease/23795.wss |url-status=dead |archive-date=May 11, 2008 |date=2008-04-02|access-date=2021-03-15 |publisher=IBM}}</ref> IBM i is sold as one of the operating system options for Power Systems (along with AIX and Linux) instead of being tied to its own hardware platform.

=== Legacy ===
Although announced in 1988, the AS/400 remains IBM's most recent major architectural shift that was developed wholly internally{{nosource|date=May 2024}}. 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 business and financial systems ran on the AS/400 platform, rumored as ending around 1999 with the introduction of [[Windows 2000]].<ref>{{cite web |author=Microsoft TechNet |url=https://groups.google.com/forum/#!msg/comp.sys.ibm.as400.misc/D8i3fBO1t1Q/uA7O-sncl-QJ |title=AS/400s extinct at Microsoft since 1999 |work=Google discussion group, Microsoft runs AS/400's in-house - Article? |access-date=2007-05-16}}</ref><ref>{{cite web |url=https://technet.microsoft.com/fr-fr/library/bb967337.aspx |title=Disparition des systèmes AS/400 chez Microsoft depuis mai 1999 | access-date=2013-01-02 |archive-url=https://web.archive.org/web/20121106083645/http://technet.microsoft.com/fr-fr/library/bb967337.aspx |archive-date=2012-11-06 |url-status=dead}}</ref><ref>{{cite web |url=http://iseriespriest.blogspot.com/2006/03/microsoft-uses-iseries-to-run-its.html |title=Microsoft Uses the iSeries to Run its Business |work=Blogspot, Confessions of An iSeries Priest |date=5 March 2006 |access-date=2006-03-05}}</ref>)