Listen to the heartbeat of SAGE (Semi-Automatic Ground Environment), IBM's giant air defense computer, in this propaganda ... I mean, educational ... film from approximately 1956. Weighing in 250 tons and using 60,000 vacuum tubes, SAGE "was the largest computer ever built." It required an acre of floor space.
When the full system of 27 SAGE computers was deployed in 1963 (each site actually consisted of two of the behemoths, one running and the other serving as a backup), long-distance telephone lines connected them with over 100 radar defense sites across the country. Perhaps not surprisingly, J.C.R. Licklider, the man who initiated research that ultimately led to the ARPANET (the granddaddy of the internet), worked on SAGE. According to another former worker, today "a seven dollar throw-away hand calculator will easily out perform the SAGE computer; and use watch batteries to do it."