History Of AS/400

The IBM System i, then known as the AS/400 (Application System/400), was the continuation of the System/38 database machine architecture (announced by IBM in October 1978 and delivered in August 1979). 

The IBM System/38 was introduced in November 1980 as a minicomputer for general business and departmental use. 

The AS/400 removed capability-based addressing. The AS/400 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 mini-computer but the architecture had reached its limit. 

The first AS/400 systems (known by the development code names Silverlake and Olympic) were delivered in 1988 under the tag line "Best of Both Worlds" and the product line has been refreshed continually since then. 

Guy Dehond from Inventive Designers was one of the beta-testers of Silverlake. The programmers who worked on OS/400, 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 one of the first general-purpose computer systems to attain a C2 security rating from the NSA (Gould UTX/C2, a UNIX-based system was branded in 1986), and in 1995 was extended to employ a 64-bit processor and operating system.

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 business and financial systems ran on the AS/400 platform.)

The 1995 change-over from 48 to 64-bit required that all programs be 'observable', i.e. that the debugging information had not been stripped out of the compiled code. This caused problems for those who had bought third-party products that had no source and no observability.

In 2008, the introduction of V6R1 caused similar problems, although this time IBM preferred to call it a "refresh".

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.

[Source: Wikipedia - http://en.wikipedia.org/wiki/IBM_System_i#History ]