A lot of people here keep mentioning mainframes and reliability/uptime. Mainframes were not particularly great at uptime (it was not a prime concern for batch p

A lot of people here keep mentioning mainframes and reliability/uptime. Mainframes were not particularly great at uptime (it was not a prime concern for batch processing), until Tandem, which was founded specifically to make fault-tolerant computers for on-line processing, started shipping systems in the late 1970s and taking market share away from IBM and the other manufacturers, forcing them to add fault tolerance.