TENDAM COMPUTERS


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INTRODUCTION

Tandem Computers, Inc. was an early manufacturer of fault-tolerant computer systems,
marketed to the growing number of transaction processing customers who used them for ATMs, banks, stock exchanges and other similar needs.
These systems use a number of independent processors and redundant storage devices to provide high-speed "failover" in the case of a hardware failure, an architecture that is named NonStop.

HISTORY

Tandem Computers was founded in 1974 by James Treybig,
who had worked up the business plan while at Kleiner & Perkins after leaving Hewlett-Packard.
Jimmy pulled together the core group from people at HP: Mike Green, Jim Katzman, and Jack Loustaunou.
Their business plan called for systems that were safe from "single-point failures" that were only marginally more expensive than competing non-fault tolerant systems.
Tandem considered this to be very important to their business model. Limiting the additional expense was important since customers often developed procedural solutions to failures when the price of fault tolerant hardware was too high.

PRODUCT DEVELOPMENT

The first system was the Tandem/16 or T/16 (later called NonStop I after the introduction of its successor, the NonStop II).
The system design was complete in 1975, and the first example was sold to Citibank in 1976.
The machine consisted of between 2 and 16 processors, each capable of about 0.7 MIPS with their own memory, I/O buses, and dual connections to their custom inter-CPU bus, called Dynabus.
The modules were constructed with dual paths so that any single failure would always leave at least one bus (both I/O and Dynabus), free for use by the other modules.
In 1993 the NonStop Himalaya K-Series using the MIPS R4400 was shipped.

FAULT TOLERANCE

The strongest demand for general-purpose fault-tolerant computing was in online database transaction and terminal-oriented applications.
In the early 1970's, vendors and customers demanding continuous availability configured multiprocessor systems as hot-standbys
These architectures, however, still contained many single points of failure.
these systems lacked thorough data integrity features, leading to problems in fault containment and possible database corruption.

NON STOP COMPUTERS

NonStop can refer to the line of HP Integrity NonStop computers, the line of Tandem NonStop computers that preceded them, or the NonStop OS operating system that is designed for them.
NonStop systems are based on an integrated hardware/software stack.
These systems are often used by banks, stock exchanges, telecommunication providers and other enterprises requiring very reliable computer systems.