History of IBM Z mainframe processors

IBM Z is both the oldest and among the most modern of computing platforms. Launched as S/360 in 1964, the mainframe became synonymous with large-scale computing for business and remains the workhorse of enterprise computing for businesses worldwide. Most of the world's largest banks, insurers, retailers, airlines, and enterprises from many other industries have IBM Z at the center of their IT infrastructure. This article presents an overview of the evolution of the IBM Z microprocessors over the past six generations. The article discusses some of the underlying workload characteristics and how these have influenced the microarchitecture enhancements driving the performance and capacity improvements. The article then describes how the focus shifted over time from speeds and feeds to new features, functions, and accelerators, and presents some examples on improved availability, enhanced security and cryptography, and embedded data compression acceleration.