Tandem Computers

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Tandem Computers, Inc.

Company type	Division
Founded	1974; 50 years ago (1974)
Founder	James Treybig
Fate	Acquired by Compaq in 1997, then by Hewlett-Packard
Headquarters	Cupertino, California
Area served	Worldwide
Products	Servers, fault tolerant computer systems
Brands	NonStop
Services	Hardware consulting, software consulting
Number of employees	12,000 at its peak

Tandem Computers, Inc. was the dominant manufacturer of fault-tolerant computer systems for ATM networks, banks, stock exchanges, telephone switching centers, 911 systems, and other similar commercial transaction processing applications requiring maximum uptime and no data loss. The company was founded by Jimmy Treybig in 1974^[1] in Cupertino, California. It remained independent until 1997, when it became a server division within Compaq. It is now a server division within Hewlett Packard Enterprise, following Hewlett-Packard's acquisition of Compaq and the split of Hewlett-Packard into HP Inc. and Hewlett Packard Enterprise.

Tandem's NonStop systems use a number of independent identical processors, redundant storage devices, and redundant controllers to provide automatic high-speed "failover" in the case of a hardware or software failure. To contain the scope of failures and of corrupted data, these multi-computer systems have no shared central components, not even main memory. Conventional multi-computer systems all use shared memories and work directly on shared data objects. Instead, NonStop processors cooperate by exchanging messages across a reliable fabric, and software takes periodic snapshots for possible rollback of program memory state.

Besides masking failures, this "shared-nothing" messaging system design also scales to the largest commercial workloads. Each doubling of the total number of processors doubles system throughput, up to the maximum configuration of 4000 processors. In contrast, the performance of conventional multiprocessor systems is limited by the speed of some shared memory, bus, or switch. Adding more than 4–8 processors in that manner gives no further system speedup. NonStop systems have more often been bought to meet scaling requirements than for extreme fault tolerance. They compete against IBM's largest mainframes, despite being built from simpler minicomputer technology.