In 1964, IBM introduced the System/360, a family of mainframe computers that, for the first time, could all run the same software, from the smallest model to the largest. Chairman Thomas J. Watson Jr. staked the company's future on the project, which industry observers estimated at some $5 billion in development costs. The architecture, led by Gene Amdahl, established conventions such as the 8-bit byte that still underpin computing today.
Before the System/360, buying a bigger computer usually meant starting over. IBM itself sold several incompatible product lines, and customers who outgrew one machine had to rewrite their programs for the next. Watson Jr. and his executives decided to replace them all with a single, compatible family spanning a wide range of price and performance. Gene Amdahl served as chief architect and Fred Brooks managed the effort. Together they defined a common instruction set and settled on the 8-bit byte and 32-bit word, choices that became industry standards. Fortune magazine captured the stakes in a headline calling the project "IBM's $5,000,000,000 Gamble," a sum larger than the company's annual revenue.
IBM launched the line with coordinated events in cities across the United States and abroad. It chartered a special train to carry reporters from New York to its facility in Poughkeepsie, and Watson called it the most important product announcement in the company's history. The initial lineup offered six processor models and dozens of peripheral devices. Customers could start small and move up without discarding their software, and emulation features allowed many older IBM programs to keep running.
The gamble nearly broke the company. Producing the new Solid Logic Technology circuits strained IBM's factories, and the operating system, OS/360, ran badly late and over budget. Brooks later drew on the experience in "The Mythical Man-Month," which argued that adding programmers to a late software project makes it later. Orders nonetheless poured in, and the System/360 made IBM the dominant force in computing for a generation. Its direct descendants, today's IBM Z mainframes, can still run programs written for the original machines.
Key people: Thomas J. Watson Jr., Gene Amdahl