The forgotten story behind IBM's 'first mainframe

 Thus, small sweet sherries all round for the birthday of IBM's S/360 mainframe, launched 40 years ago.

The venerable machine is being feted around the world as the grandfather of modern computing: it brought such innovations as lookahead, pipelining, branch prediction, multitasking, memory protection, generalised interrupts, and the 8-bit byte to the commercial market. For those of us who've been brought up on a diet of microprocessor roadmaps, it's a welcome reminder that the latest, greatest chips depend on inventions dating back to the days when the Beatles still wanted to hold your hand.

t is no coincidence that the end of the Second World War saw the start of digital computing. As well as the now-famous work done by Turing and others at Bletchley Park, atomic weaponry research in the US had proved two things -- that nuclear and thermonuclear bombs would define the course of the rest of the century, and that designing the things required more sums to be done than was humanly possible. The push for high-powered computation was on.

By 1955, the University of California Radiation Lab was looking for a computer faster than ever before. IBM bid but lost to Univac -- then the biggest computer company -- and IBM hated to lose. The company came back a year later with a proposal for Los Alamos labs for a computer with "a speed at least a hundred times greater" than existing machines. It won that one, and had four years to deliver the beast. The project was officially called the 7030, but was far better known as Project Stretch -- it would stretch every aspect of computing.

The innovations began right at the start. Stretch would be built with a brand-new invention, the transistor, and it was the first design to rely on a simulator. This was built by John Cocke and Harwood Kolsky early on, and let the designers try out new ideas before committing them to the final machine -- a method of working that has since become universal.

It's hard to list all the ideas that Stretch embodied and that have since become canon law in processor design. It could fetch and decode multiple instructions simultaneously -- remember the superscalar hype of the late 90s? -- and pipelined them, decoupling decoding and execution. It could predict the results of calculations and speculatively execute code depending on its best guess, and could look ahead to unexecuted instructions to make the best use of its internal resources.

So, while you toast the success of the S/360 -- another small sherry? -- remember that it and almost everything else you'll touch with a chip inside is the inheritor of a burst of unmatched innovation, one that flowered years before, in the unholy light of Trinity.