Sinclair Computers

Sir Clive Sinclair, the founder of Sinclair Research, was a habitual inventor and entrepreneur who received much press attention in the 1980s (not all good: for example, the coverage related to Sinclair’s C5 electric vehicle). Sinclair’s first company, Sinclair Radionics, produced radio sets using rejected computer transistors bought from Plessey Components. The company later moved into the calculator market, producing a pocket calculator called the Sinclair Executive for the price of £79, and then a few years later the Sinclair Cambridge — described by Sinclair in an interview as “the world’s first single chip scientific calculator — the first cheap one too” [3] — for £43.95 fully assembled.

Later, after a brief flirtation with the digital watch, Sinclair moved into the manufacture of computers. Firstly, at Sinclair Radionics (which Sinclair later left after the Government-run National Enterprise Board acquired a stake in the firm) the design project for the NewBrain was started: this computer was to become first proposed design for the BBC microcomputer. However, the company was unable to deliver a completed product on time, meaning that the Corporation had to look for another design elsewhere. After leaving Sinclair Radionics, Sinclair founded Science of Cambridge, which was later renamed Sinclair Research. This company designed and sold a new computer kit, known as the MK14. Initially designed by employee Ian Williamson, the MK14 used the National Semiconductor Microprocessor (National SC/MP). The design of the kit was eventually changed to use National Semiconductor components throughout. This primitive kit computer was not as impressive as its rival Nascom 1: it did not come with a full keyboard, for a start. However, the machine became more popular than was expected at launch, probably aided by an “extravagant advertising campaign” [1]. In a theme that was to run through the entire history of Sinclair Research, the company was initially unable to keep up with demand.

ZX80 and ZX81
The innovative sub-£100 microcomputer cited by so many is the ZX80. It was produced in 1980 by Science of Cambridge after the relative success of the MK14, which had “proved to Clive Sinclair that microcomputers were a worthwhile product” [2]. Initially sold by mail order, Sinclair was yet again unprepared for the demand. Newspaper advertising by Sinclair in 1980 stated that “inside a day, you’ll be talking to it like an old friend!” and that “if computers interest you—and today, computers should interest everybody—you’ll find the ZX80 totally absorbing”. While this advertising blurb may have not have encouraged everybody, Sinclair had sold over 20,000 ZX80s by September of that year [2]. However, the machine was described by Ian Adamson and Richard Kennedy as not representing “a development of existing technology, merely its competent application” [1]. For instance, the machine only came with 1kB of RAM, and was not capable of handling floating-point arithmetic.<!-- compared with others? -->

The successor to the ZX80 was the ZX81, which was the first Sinclair microcomputer to be sold in high street shops [1]. The computer sold very successfully in the stores of W. H. Smith, despite the initial scepticism of many of a number of buyers at the company: “Negative feedback from the shopfloor was rapidly reversed by an overwhelmingly enthusiastic market response. In the year following the ZX81’s appearance in the high street, W. H. Smith sold in excess of 350,000 machines and banked a net profit of around £10 million … This figure assumes a ZX81 purchase price of £69.95 and the 40 per cent retailer’s discount quoted by W. H. Smith” [1]. The ZX80 and ZX81 were certainly very popular: their low price, if not their level of functionality, made them a popular choice, as the sales figures at W H Smith indicate. Companies quickly appeared that offered add-on peripherals for the machines; indeed, W H Smith themselves offered an own-label cassette recorder for the ZX81. A sign of the popularity of the Sinclair computers — and indeed of microcomputers in general — was that 10,000 people attended a computer fair dedicated to Sinclair computers in January 1982 [2]. The media quickly started a microcomputer frenzy, hailing them as a massive technological advance: for instance, The Sun described Sinclair as “the most prodigious inventor since Leonardo” (cited in [1]).

However, not all were positive about the Sinclair machines. For instance, Paul Kriwaczek, producer of the BBC’s The Computer Programme, described the ZX81 as “a throwaway consumer product” [1], because its capacity for expansion was limited. A Sinclair machine was ultimately not chosen for the BBC’s Computer Literacy Project; instead, the more advanced ‘Proton’ designed by Acorn Computers was chosen as the basis for the BBC Micro. In addition, the decision to use a membrane keyboard with ZX80, ZX81 and Spectrum was controversial, being more difficult to use than a conventional keyboard: one group of contemporary commentators wrote that “the only group to benefit from this policy has been the peripheral manufacturers, who have provided a wide range of alternative keyboards” [1].

ZX Spectrum
The ZX81 was followed by the Sinclair ZX Spectrum. This was the first Sinclair microcomputer to be eligible for the British Government’s Micros in Schools grant. Available in two versions (with either 16 or 48 kilobytes of memory, with the 16kB model being upgradable by purchasing an expansion pack), the Spectrum was arguably the company’s most successful product. A number of peripherals were offered for the Spectrum, including the ZX Microdrive: a tape based device, where “the cartridges … contain a loop of 200 inches of magnetic video tape on which 85K of data can be stored. Although considerably slower and less flexible than a disc system, the Microdrive can nevertheless load a 48K program in about 4 seconds” [1]. This was a considerable improvement compared to the slow, and often unreliable, cassette tape based system. The Spectrum spawned an entire ‘cottage industry’ of individual programmers, producing software for the machine: mainly games, but also some productivity software as well.

Mark New

[1] I. Adamson and R. Kennedy. Sinclair and the “Sunrise” Technology. Penguin Books, 1986.
[2] R. Dale. The Sinclair Story. Duckworth, 1985.
[3] C. Langdon and D. Manners. Digerati Glitterati. John Wiley and Sons, 2001.