What if computers went back to the '70s too?

The legendary scientific box was the PDP-8 – small enough to put on a trolley and wheel from lab to lab. You fed your paper tape into the sprocket, and then initiated the run, and carefully stored the results on another paper tape. Nobody dreamed of using those things for commercial apps. But you didn't need to have an office next to a hospital to afford the electricity, and so when the PDP-8's big brother the PDP-11 arrived, people did start wondering if these "programmable data processors" might be useable as, well, computers?

What's odd, is that the question hadn't been asked before. After all, not only Honeywell and imitators like Prime, but IBM itself actually built and sold minicomputers from the mid-60s (when IBM's 1130 appeared) and specifically provided standard computing abilities. And, probably, the key is in the price.

When DEC launched the PDP-8, it cost as little as $16,000 (and remember, the dollar was worth nearly three pounds sterling in those days) while the 1130 cost upwards of $33,000. In the early 70s big iron was getting bigger and more expensive and little iron was much more affordable by cash-strapped companies.

What probably made the difference was the PDP-11 and, very soon after it was launched, a development with an impact very like the later arrival of Visual Basic: something called RSTS. Resource Sharing Time Sharing was an operating system which allowed relatively untrained programmers to load Basic programs, and run them in their own time-sharing portion of the PDP-11.

Professional programmers liked the RSX-11 operating system, but you could stick RSTS on a DEC box and just let amateurs have a play, over a dumb terminal. Inelegant, perhaps, but no need to wait for programming staff to get round to your request. The same advantage gave us the PC boom in the early 80s, of course. But there you could actually buy your own system, disks and printer and all, without waiting for the go-ahead of the DP manager. DEC-11s were still far outside the budget of any individual manager.

The mid-70s boom in PDP-11s caught the industry by surprise. The recession probably eased faster than people appreciated - the improvement was concealed behind catastrophes like the devaluation of the pound sterling and several short-term boom and bust cycles. But also the world really hadn't got a clue what computers were for before 1975. By 1980, everybody had caught on.

The results were catastrophic for one company: Texas Instruments, though at the time it didn't seem like a catastrophe. What happened was that DEC had hopelessly underestimated the demand for the PDP-11 range, and waiting times went way out into the future. At one stage, companies like Systime were forced to start building their own DEC-compatible memory and storage devices, simply so as to be able to ship systems, because the waiting list (officially) was three years.

Nobody could put a project on hold that long, and so rival companies thrived.

Data General burst out of DEC like a moth out of a chrysalis in 1968, launching the Nova in 1969, and without that initiative to spur DEC on it might be that the PDP-11 wouldn't have seen daylight. Edson deCastro left DEC when DEC founder Olsen turned down the fanciful concept of a 16-bit architecture. The Nova was so successful that DEC rapidly reversed its decision and definitely beat Data General at the 16-bit game. And DG nonetheless thrived, launching its SuperNova.

Texas's mistake was to launch a minicomputer called the 990 which was just about good enough to sell as a general purpose computer. Its even worse mistake was to launch a 16-bit microprocessor chip based on the 99 architecture: the 9900.

The 9900 was the first true 16-bit microprocessor and the company planned a secret range of personal computers based on it – a range which would without doubt have dominated the market. The reason it didn't was simple: it was never launched. And the reason it was not launched was stupid: it was seen as a rival to the success of the 990 mini.

The main problem with the 9900 chip was price: it was loads cheaper than the 990 systems. Excellent! And the idea was greeted by those of us who saw the secret designs for genuine home computers and personal office computers with enthusiasm, because the market genuinely wanted something like this. But the three-year shortage of DEC PDP-11 models meant that TI was shipping every 990 machine it could make.

The board decided to scrap the two top-end personal computers and limit itself to a cut-down 99/4 toy, deliberately hobbled to ensure that nobody could ever try to run an office system with it.

The growth of minis wasn't limited to "fake servers", however. Comms was exploding just as hard, and a Honeywell clone-maker, Prime, was poised to explode with it. In the UK, a similar boom with Prestel was about to inflate GEC and its 4000 family of minis.

You might like to speculate, as we say farewell to the genuine minis of the 70s, about just what British computing might have become if the minis that side of the Pond could have been used for more world-wide comms applications, and if BT hadn't insisted on developing its own System X switching computers (unsellable to any other country). It would probably be dreaming, because GEC, Plessey and Ferranti never showed any interest in general purpose computing. But it's an interesting dream, all the same. ®