Tandem Computers

» see tandem.com as it lived, on the wayback machine

~ the eulogy ~

Jimmy Treybig was running a marketing team in Hewlett-Packard's HP 3000 division when he worked out that there was a market for a computer that did not go down. HP was not interested. He went to Kleiner Perkins and wrote the business plan there, then in 1974 started a company a quarter of a mile from the HP offices, staffed largely by engineers he took with him. The plan promised systems with no outages and no lost or corrupted data, built so that no single point of failure existed anywhere in them, at a price only marginally above ordinary machines.

The design of the Tandem/16 was finished in 1975 and the first system shipped to Citibank in may 1976. From there the customer list wrote itself: the places where a computer stopping is not an inconvenience but an incident. Cash machine networks and stock exchanges first, then telephone switches and emergency call systems. By 2002, running inside Compaq by then, NonStop machines were handling ninety five percent of the world's stock transactions and two thirds of its credit card transactions.

Growth was uninterrupted through 1983, and at one point Inc. magazine called Tandem the fastest growing public company in America. By 1996 it was a $2.3 billion business with roughly eight thousand employees. That was also the year the growth stopped, Treybig left after twenty two years, and the company started describing itself as a Windows and Intel platform to whoever was listening. Compaq was listening. The merger agreement was announced on 23 june 1997 and took effect on 29 august, after Tandem shareholders voted it through.

A cash machine is one of the few computers an ordinary person trusts with an absolute guarantee. You put a card into a wall in Ankara at midnight and either the money comes out and the balance moves, or neither happens, and nobody standing there has ever spent a second considering the third option. I have used those machines for my entire adult life without once wondering what was at the other end of the line. For a very large share of the world's banks, what was at the other end was a Tandem.

~ the dossier ~

~ how it worked ~

Conventional multiprocessor machines of the era shared memory and worked directly on shared objects, which meant a corrupted structure was corrupted for everybody and a failed component took the system with it. NonStop went the other way and shared nothing at all. Independent identical processors sat behind duplicated storage and duplicated controllers, with no common main memory anywhere. Processors cooperated by passing messages over a reliable fabric, and the software took periodic snapshots so a failed process could be rolled back and restarted somewhere else.

The side effect turned out to be as valuable as the goal. Because nothing was shared, nothing became a bottleneck, so doubling the processor count doubled the throughput right up to four thousand processors. Conventional designs ran out of headroom somewhere around eight. Plenty of customers bought NonStop machines purely because they scaled and treated the fault tolerance as a bonus they hoped never to test.

~ the beer bust ~

Treybig's original business plan contained a section on the culture he wanted, which was unusual enough in 1974 that people still bring it up. Every employee got a six week paid sabbatical every four years. Every employee got a hundred shares of stock a year. Friday afternoons were an all hands party the company called the beer bust, and once a month there was a closed circuit telecast to every office in the world so nobody found out what was happening from a rumor.

None of that is why the machines sold. It is why people who worked there in the seventies and eighties still talk about it as the best job they ever had, and why the Silicon Valley perks industry that arrived twenty years later was reinventing something rather than inventing it.

~ the sale ~

Compaq's problem in 1997 was that it sold personal computers brilliantly and had almost nothing at the top of the market. Tandem's problem was that it had spent a decade being the answer to a question fewer companies were asking out loud, even as their transactions kept running through its boxes. Three billion dollars in stock resolved both, and about sixty two million Compaq shares changed hands to do it.

Then the acquisitions kept happening on top of it. Compaq bought Digital Equipment the following year, which meant Tandem's engineers were told to abandon their port of NonStop to Itanium and target Alpha instead. In 2001 Compaq killed Alpha before a single Alpha NonStop shipped, and the port went back to Itanium. HP bought Compaq in 2002, split itself in 2015, and NonStop landed inside Hewlett Packard Enterprise, where it eventually moved to ordinary x86 chips.

~ the long tail ~

The thing that makes Tandem strange as a grave is that the product never died. NonStop is still sold and still runs bank transaction workloads on design decisions made in a Cupertino office in 1975. What ended in august 1997 was the company and the culture Treybig wrote into a business plan before there was anything to run it on.

That is the ordinary fate of a company whose customers cannot afford disruption. Nobody rips out a system that has never failed, so the machines outlast every corporate parent that inherits them, and the name on the invoice changes four times while the workload underneath does not notice. Tandem sold reliability and got taken at its word for fifty years.

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