Operational from the 1950s to 1980s and costing an estimated $8 - $12 billion USD, the Semi-Automatic Ground Environment (SAGE) consisted of a network of 23 pairs of 250-ton AN/FSQ-7 computers, the largest computers ever built, each housed in a 4-story, 3.5-acre concrete blockhouse. Each center held two AN/FSQ-7s, with one acting as a backup in case the other became non-operational. The computers were networked with local radar systems and provided directional data to manned aircraft and Bomarc surface-to-air missiles to provide a first line of defense against Soviet nuclear bombers.聽
Though useless against intercontinental ballistic missiles, the SAGE system was a remarkable feat of engineering and pioneered many communications, networking, real-time computing and display technologies, and was at its time the largest software engineering project ever undertaken. While it possessed computational power equivalent to an Intel 386, SAGE鈥檚 computers were capable of processing large volumes of data, controlling both manned and unmanned aircraft, supporting hundreds of user terminals and communicating across networks.聽