Meaning – The term S/390, refers to the family of IBM enterprise servers that demonstrate outstanding reliability, availability, scalability, security, and capacity in todayi?s network computing environments.

These were followed by the 9672 CMOS System/390 mainframe family in the mid-1990s. These systems followed the IBM 3090, with over a decade of follow-ons. The ESA/390 was succeeded by the 64-bit z/Architecture in 2000.

The architecture (the Linux kernel architecture designation is “s390”; “s390x” designates the 64-bit z/Architecture) employs a channel I/O subsystem in the System/360 tradition, offloading almost all I/O activity to specialized hardware. It also includes a standard set of CCW opcodes that new equipment is expected to support.

Example of usage“The architecture maintains problem state backward compatibility with the 24-bit-address/32-bit-data System/360 (1964) and subsequent 24/31-bit-address/32-bit-data architectures (System/370, System/370-XA, ESA/370, and ESA/390. However, the I/O subsystem is based on System/370 Extended Architecture (S/370-XA), not on the original S/370 I/O instructions.”