IBM System/390

The IBM System/390 is a discontinued mainframe product family implementing ESA/390, the fifth generation of the System/360 instruction set architecture. The first computers to use the ESA/390 were the Enterprise System/9000 (ES/9000) family, which were introduced in 1990. These were followed by the 9672, Multiprise, and Integrated Server families of System/390 in 1994–1999, using CMOS microprocessors. The ESA/390 succeeded ESA/370, used in the Enhanced 3090 and 4381 "E" models, and the System/370 architecture last used in the IBM 9370 low-end mainframe. ESA/390 was succeeded by the 64-bit z/Architecture in 2000. On September 5, 1990, IBM published a group of hardware and software announcements, two of which included overviews of three announcements: System/390 (S/390), as in 360 for 1960s, 370 for 1970s. Enterprise System/9000 (ES/9000), as in 360 for 1960s, 370 for 1970s. Enterprise Systems Architecture/390 (ESA/390) was IBM's last 31-bit-address/32-bit-data mainframe computing design, copied by Amdahl, Hitachi, and Fujitsu among other competitors. It was the successor of ESA/370 and, in turn, was succeeded by the 64-bit z/Architecture in 2000. Among other things, ESA/390 added fiber optics channels, known as Enterprise Systems Connection (ESCON) channels, to the parallel (Bus and Tag) channels of ESA/370. Despite the fact that IBM mentioned the 9000 family first in some of the day's announcements, it was clear "by the end of the day" that it was "for System/390," although it was a shortened name, S/390, that was placed on some of the actual "boxes" later shipped. The ES/9000 include rack-mounted models, free standing air cooled models and water cooled models. The low end models were substantially less expensive than the 3090 or 4381 previously needed to run MVS/ESA, and could also run VM/ESA and VSE/ESA, which IBM announced at the same time. IBM periodically added named features to ESA/390 in conjunction with new processors; the ESA/390 Principles of Operation manual identifies them only by name, not by the processors supporting them.