IBM AS/400

Although not technically a home computer, far from it, this machine has made a significant impact on the computer world, and many folks have had their first interaction with computers on an AS/400 system.

The original AS/400, or Application System/400, was introduced by IBM in 1988 as a midrange computer designed for business applications. It is known for its reliability, its integrated database, and robust transaction processing capabilities.

Technical Specifications

The AS/400 originally used the Internal Microprogrammed Processor Interface, or the IMPI. This was a CPU based on CISC architecture that IBM developped for their System/38 range of computers. The processor typically had a clock speed of 8MHz up to 16MHz, which was typical for the era. Not so typical was the 48-bit architecture. Most computers of that time used either a 8, 16, or 32-bit architecture, so this was quite uncommon. The system was heavily microcode-driven wich provided signicifant flexibility and allowed the AS/400 to support a wide range of applciations.

Memory and Storage

RAM could be configured between 2MByte up to 256MByte. The AS/400 had advanced memory management features for its time, including a virtual storage architecture to manage memory more efficiently and effectively. Storage was provided by disk, which could range from 70MByte to several GigaByte, depending on the configuration. The AS/400 included the DB2/400 relational database as part of the core operating system OS/400. The database had a single-level storage model that abstracted physical and logical storage, presenting a single address space for applications, simplifying memory management.

Operation

The AS/400 was operated through IBM's 5250 terminals, using the twin-axial communication protocol. The system supported Twinax, Ethernet and other networking protocols such as the proprietary Systems Network Architecture (SNA). The AS/400 was optimized for high transaction-processing performance targeting industries such as banking, retail, and manufacturing. It was designed to scale from small businesses to large enterprises by simply upgrading the hardware without the need for different software.