ZX Spectrum
The ZX Spectrum is an 8-bit home computer developed and marketed by Sinclair Research. The Spectrum played a pivotal role in the history of personal computers and video games, especially in the United Kingdom. It was one of the all-time bestselling British computers with over five million units sold. It was released in the UK on 23 April 1982, the United States in 1983, and Europe in 1984.
The machine was designed by the English entrepreneur and inventor Sir Clive Sinclair and his small team in Cambridge, and was manufactured in Dundee, Scotland by Timex Corporation. It was made to be small, simple, and most importantly inexpensive, with as few components as possible. The addendum "Spectrum" was chosen to highlight the machine's colour display, which differed from the black-and-white display of its predecessor, the ZX81. Rick Dickinson designed its distinctive case, rainbow motif, and rubber keyboard. Video output is transmitted to a television set rather than a dedicated monitor, while application software is loaded and saved onto compact audio cassettes.
The ZX Spectrum was initially distributed by mail order, but after severe backlogs it was sold through High Street chains in the United Kingdom. It was released in the US as the Timex Sinclair 2068 in 1983, and in some parts of Europe as the Timex Computer 2048. There are seven models overall, ranging from the entry level with 16 KB RAM released in 1982 to the ZX Spectrum +3 with 128 KB RAM and built-in floppy disk drive in 1987. The machine primarily competed with the Commodore 64, BBC Micro, Dragon 32, and the Amstrad CPC range. Over 24,000 software products were released for the ZX Spectrum.
Its introduction led to a boom in companies producing software and hardware, the effects of which are still seen. It was among the first home computers aimed at a mainstream UK audience, with some crediting it for launching the British information technology industry. The Spectrum was Britain's top-selling computer until the Amstrad PCW surpassed it in the 1990s. It was discontinued in 1992.
History
The ZX Spectrum was conceived and designed by engineers at Sinclair Research, founded by English entrepreneur and inventor Clive Sinclair, who was well known for his eccentricity and pioneering ethic. On 25 July 1961, three years after passing his A-levels, he founded Sinclair Radionics to advertise his inventions and buy components. In 1972, Sinclair competed with Texas Instruments to produce the world's first pocket calculator, the Sinclair Executive. By the mid 1970s, Sinclair Radionics was producing handheld electronic calculators, miniature televisions, and the ill-fated digital Black Watch wristwatch. Due to financial losses, Sinclair sought investors from the National Enterprise Board, who had bought a 43% interest in the company and streamlined his product line. Sinclair's relationship with the NEB had worsened, and by 1979 it opted to break up Sinclair Radionics entirely, selling off its television division to Binatone and its calculator division to ESL Bristol.After incurring a £7 million investment loss, Sinclair was given a golden handshake and an estimated £10,000 severance package. He had a former employee, Christopher Curry, establish a "corporate lifeboat" company named Science of Cambridge Ltd, in July 1977, called such as they were located near the University of Cambridge. By this time inexpensive microprocessors had started appearing on the market, which prompted Sinclair to start producing the MK14, a computer teaching kit which sold well at a very low price. Encouraged by this success, Sinclair renamed his company to Sinclair Research, and started looking to manufacture personal computers. Keeping the cost low was essential for Sinclair to avoid his products from becoming outpriced by American or Japanese equivalents as had happened to several of the previous Sinclair Radionics products. On 29 January 1980, the ZX80 home computer was launched to immediate popularity; notable for being one of the first computers available in the United Kingdom for less than £100. The company conducted no market research whatsoever prior to the launch of the ZX80; according to Sinclair, he "simply had a hunch" that the public was sufficiently interested to make such a project feasible and went ahead with ordering 100,000 sets of parts so that he could launch at high volume.
On 5 March 1981, the ZX81 was launched worldwide to immense success with more than 1.5 million units sold, 60% of which was outside Britain. According to Ben Rosen, by pricing the ZX81 so low, the company had "opened up a completely new market among people who had never previously considered owning a computer". After its release, computing in Britain became an activity for the general public rather than the preserve of office workers and hobbyists. The ZX81's commercial success made Sinclair Research one of Britain's leading computer manufacturers, with Sinclair himself reportedly "amused and gratified" by the attention the machine received.
Development
Development of the ZX Spectrum began in September 1981, a few months after the release of the ZX81. Sinclair resolved to make his own products obsolete before his rivals developed the products that would do so. Parts of designs from the ZX80 and ZX81 were reused to ensure a speedy and cost-effective manufacturing process. The team consisted of 20 engineers housed in a small office at 6 King's Parade, Cambridge. During early production, the machine was known as the ZX81 Colour or the ZX82 to highlight the machine's colour display, which differed from the black and white of its predecessors. The addendum "Spectrum" was added later on, to emphasise its 15-colour palette. Aside from a new crystal oscillator and extra chips to add additional kilobytes of memory, the ZX Spectrum was intended to be, as quoted by Sinclair's marketing manager, essentially a "ZX81 with colour". According to Sinclair, the team also wanted to combine the ZX81's separate random-access memory sections for audio and video into a single bank.Chief engineer Richard Altwasser was responsible for the ZX Spectrum's hardware design. His main contribution was the design of the semi-custom uncommitted logic array integrated circuit, which integrated, on a single chip, the essential hardware functions. Altwasser designed a graphics mode that required less than 7 kilobytes of memory and implemented it on the ULA. Vickers wrote most of the ROM code. Lengthy discussions between Altwasser and Sinclair engineers resulted in a broad agreement that the ZX Spectrum must have high-resolution graphics, 16 kilobytes of memory, an improved cassette interface, and an impressive colour palette. To achieve this, the team had to divorce the central processing unit away from the main display to enable it to work at full efficiency – a method which contrasted with the ZX81's integrated CPU. The inclusion of colour proved a major obstacle to the engineers. A Teletext-like approach was briefly considered, in which each line of text would have colour-change codes inserted into it. This was deemed unsuitable for high-resolution graphs or diagrams that involved multiple colour changes. Altwasser devised the idea of allocating a colour attribute to each character position on the screen. This ultimately used eight bits of memory for each character position; three bits to provide any one of eight foreground colours and three bits for the eight background colours, one bit for extra brightness and one bit for flashing. Overall, the system took up slightly less than 7 kilobytes of memory, leaving an additional 9 kilobytes to write programs – a figure that pleased the team.
Much of the firmware was written by computer scientist Steve Vickers from Nine Tiles, who compiled all control routines to produce the Sinclair BASIC interpreter, a custom variant of the general purpose BASIC programming language. Making a custom interpreter made it possible to fit all of its functionality into a very small amount of read-only memory. The development process of the software was marked by disagreements between Nine Tiles and Sinclair Research. Sinclair placed an emphasis on expediting the release of the Spectrum, primarily by minimising alterations in the software from the ZX81, which had in turn been based on the ZX80's software. The software architecture of the ZX80, however, had been tailored for a severely constrained memory system, and in Nine Tiles' opinion was unsuitable for the enhanced processing demands of the ZX Spectrum. Sinclair favoured solving this with expansion modules on the existing framework like with the ZX81, which Nine Tiles disagreed with. Ultimately, both designs were developed, but Vickers and Nine Tiles were unable to finish their version before the launch of the Spectrum and it was not used.
File:Rick Dickinson.jpg|thumb|left|Designer Rick Dickinson in the Sinclair Research Cambridge office in 1983
The distinctive case and colourful design of the ZX Spectrum was the creation of Rick Dickinson, a young British industrial designer who had been hired by Sinclair to design the ZX81. Dickinson was tasked to design a sleeker and more "marketable" appearance to the new machine, whilst ensuring all 192 BASIC functions could fit onto 40 physical keys. Early sketches from August 1981 showed the case was to be more angular and wedge-like, in similar vein to an upgraded ZX81 model. Dickinson later settled on a flatter design with a raised rear section and rounded sides in order to depict the machine as "more advanced" as opposed to a mere upgrade. In drawing up potential logos, Dickinson proposed a series of different logotypes which all featured rainbow slashes across the keyboard.
The design of the Spectrum's rubber keyboard was simplified from several hundred components to a conventional moving keyboard down to "four to five" moving parts using a new technology. The keyboard was still undergoing changes as late as February 1982; some sketches included a roundel-on-square key design which was later featured on the later Spectrum+ model. Dickinson recalled in 2007 that "everything was cost driven" and that the minimalist, Bauhaus approach to the Spectrum gave it an elegant yet " revolutionary" form. The drawing board on which Dickinson designed the ZX Spectrum is now on display in the Science Museum in London.
The need for an improved cassette interface was apparent from ZX81 users who encountered problems trying to save and load programs. To increase the data transfer speed, the team decreased the length of tones that represent binary data. Originally, the team aimed for 1000 baud, but succeeded in reaching a considerably faster 1500 baud. To increase reliability, a leading period of constant tone was introduced, allowing the cassette recorder's automatic gain control to settle down, eliminating hisses on the tape. A Schmitt trigger was added inside the ULA to reduce noise of the received signal. Unlike the ZX81, the Spectrum is able to maintain its display during data transfer, allowing programs to show a splash screen whilst loading.
As with the ZX81, the ZX Spectrum was manufactured in Dundee, Scotland, by Timex Corporation at the Dryburgh factory. Prior to the ZX81, Timex was an established manufacturer of mechanical watches, but had little experience in assembling electronics. Timex's director, Fred Olsen, determined that the company would diversify into other areas and signed a contract with Sinclair.