ZX Spectrum
On the 25th of July 1961, three years after passing his A-levels, Clive Sinclair founded Sinclair Radionics to advertise his inventions and buy components. By 1972, he competed with Texas Instruments to produce the world's first pocket calculator, the Sinclair Executive. The mid-1970s saw Sinclair Radionics producing handheld electronic calculators, miniature televisions, and the ill-fated digital Black Watch wristwatch. Financial losses forced Sinclair to seek investors from the National Enterprise Board (NEB), who bought a 43% interest in the company. By 1979, the NEB 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 received an estimated £10,000 severance package. He had former employee Christopher Curry establish Science of Cambridge Ltd in July 1977. Inexpensive microprocessors started appearing on the market, prompting Sinclair to start producing the MK14 computer teaching kit which sold well at a very low price. Encouraged by this success, Sinclair renamed his company to Sinclair Research and began looking to manufacture personal computers. Keeping costs low was essential for Sinclair to avoid his products becoming outpriced by American or Japanese equivalents as had happened to several previous Sinclair Radionics products. On the 29th of January 1980, the ZX80 home computer 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.
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 essentially a ZX81 with colour. 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 essential hardware functions on a single chip. 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 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. 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.
The ZX Spectrum was officially revealed before journalists by Sinclair at the Churchill Hotel in Marylebone, London, on the 23rd of April 1982. Later that week, the machine was presented in a blaze of publicity at the Earl's Court Computer Show in London, and the ZX Microfair in Manchester. The ZX Spectrum launched with two models: a 16KB basic version, and an enhanced 48KB variant. The former model had an undercutting price of £125, significantly lower than its main competitor the BBC Micro, whilst the latter model's price of £175 was comparable to a third of an Apple II computer. Upon release, the keyboard surprised many users due to its use of rubber keys, described as offering the feel of dead flesh. Sinclair himself remarked that the keyboard's rubber mould was unusual, but consumers were undeterred. Despite very high demand, Sinclair Research was notoriously late in delivering the ZX Spectrum. Their practice of offering mail-order sales before units were ready ensured a constant cash flow, but meant a lacking distribution. Nigel Searle, the newly-appointed chief of Sinclair's computer division, said in June 1982 the company had no plans to stock the new machine in WHSmith, which was at the time Sinclair's only retailer. Searle explained that the mail-order system was in place due to there being no obvious retail outlets in the United Kingdom which could sell personal computers, and it made better sense financially to continue selling through mail-order. The company's conservative approach to distributing the machine was criticised, with disillusioned customers telephoning and writing letters. Demand sky-rocketed beyond Sinclair's planned 20,000 monthly unit output to a backlog of 30,000 orders by July 1982. Due to a scheduled holiday at the Timex factory that summer, the backlog had risen to 40,000 units. Sinclair issued a public apology in September that year, and promised that the backlog would be cleared by the end of that month. Supply did not return to normal until the 1982 Christmas season.
Production of the machine rapidly increased with the arrival of the less expensive Issue 2 motherboard, a redesign of the main circuit board which addressed hardware manufacturing defects that affected production of the first model. Sales of the ZX Spectrum reached 200,000 in its first nine months, rising to 300,000 for the whole of the first year. By August 1983 total sales in Britain and Europe had exceeded 500,000, with the millionth Spectrum manufactured on the 9th of December 1983. An Issue 1 ZX Spectrum can be distinguished from Issue 2 or 3 models by the colour of the keys , light grey for Issue 1, blue-grey for later machines. Although the official service manual states that approximately 26,000 of these original boards were manufactured, subsequent serial number analysis shows that only 16,000 were produced, almost all of which fell in the serial number range 001-000001 to 001-016000. In March 1983, Sinclair issued an urgent recall warning for all owners of models bought after the 1st of January 1983. Plugs with a non-textured surface were at risk of causing shock, and were asked to be sent back to a warehouse in Cambridgeshire which would supply a replacement within 48 hours. Development of the ZX Spectrum+ began in June 1984, and was released on the 15th of October that year at £179. It was assembled by AB Electronics in South Wales and Samsung in South Korea. This 48 KB Spectrum introduced a new QL-style case with an injection-moulded keyboard and a reset button that functions as a switch shorting across the CPU reset capacitor. Electronically, it was identical to the previous 48 KB model. The machine outsold the rubber-key model two to one, however, some retailers reported a failure rate of up to 30%, compared with a more typical 5, 6% for the older model.
Most Spectrum software was originally distributed on audio cassette tapes, intended to work with consumer cassette recorders. Software was also distributed through type-in program listings in magazines and books. The reader entered a program by hand and saved it to cassette for later use. Some magazines distributed 7 inch 33 rpm flexi disc records, or Floppy ROMs, a variant of regular vinyl records which could be played on a standard record player. Some radio stations broadcast audio stream data via frequency modulation or medium wave so listeners could directly record it onto an audio cassette themselves. ZX Spectrum-focused radio programmes existed in the United Kingdom, which were received over long distances on domestic radio receivers. Software released for the machine includes programming languages, databases, word processors, spreadsheets, drawing and painting tools, 3D-modelling and archaeology software. Over 24,000 different software titles were released for the ZX Spectrum throughout its lifespan. Beginning in August 1982 the ZX Spectrum was bundled with Horizons: Software Starter Pack, a compilation of ten demonstration programs. The ZX Spectrum has an extensive library of video games which established it as a prominent gaming platform in the 1980s, including Manic Miner, Jet Set Willy, Chuckie Egg, Elite, Sabre Wulf, Knight Lore, and The Hobbit. Ant Attack is the first video game with isometric graphics, Turbo Esprit, the first open world driving game, and Redhawk features the first superhero created specifically for a video game.
Sinclair Research granted a licence for the ZX Spectrum design to the Timex Corporation in the United States. Timex marketed several computer models under the Timex Sinclair brand. They introduced an enhanced variant of the original Spectrum in the US, known as the Timex Sinclair 2068. This upgraded model features improvements in sound, graphics, and various other aspects. However, Timex's versions were generally not compatible with Sinclair systems. Timex of Portugal developed and produced several branded computers, including a PAL region-compatible version of the Timex Sinclair 2068, known as the Timex Computer 2048. This variant features distinct buffers for both the ULA and the CPU, significantly enhancing compatibility with ZX Spectrum software compared to the American model. Software developed for the Portuguese-made 2048 remained fully compatible with its American counterpart, as the ROMs were left unaltered. In India, Deci Bells Electronics Limited based in Pune, introduced a licensed version of the Spectrum+ in 1988. Dubbed the dB Spectrum+, it performed well in the Indian market, selling over 50,000 units and achieving an 80% market share. Numerous unofficial Spectrum clones were produced, especially in Eastern Europe. Many small start-ups in the Soviet Union assembled various clones, distributed through poster adverts and street stalls. Over 50 such clone models existed in total. In Czechoslovakia, the first production ZX Spectrum clone was the Didaktik Gama, sporting two switched 32 KB memory banks and 16 KB of slower RAM containing graphical data for video output.
The role of the ZX Spectrum in the history of personal computers and video games made it one of the most important and influential computers of the 1980s. Some observers credit it as being responsible for launching the British information technology industry during a period of recession, while introducing home computing to the masses. By the end of the Spectrum's lifespan in 1992, it is also one of the best-selling British computers of all time, with over five million units sold. It retained the title of Britain's top-selling computer until the Amstrad PCW surpassed it in the 1990s, with eight million units sold by the end of the PCW's lifespan in 1998. The ZX Spectrum was popular in communist Czechoslovakia, with an estimated 100,000 in the country by 1988 making it the most popular home computer of the time. This was despite only briefly being officially distributed, and never advertised. Its small size made it easier to smuggle into the country to avoid high customs fees. A number of notable game developers began their careers on the ZX Spectrum. Tim and Chris Stamper founded Ultimate Play the Game in 1982, who found success with Jetpac, Atic Atac, Sabre Wulf, and Knight Lore. The Stamper brothers later founded Rare, which became Nintendo's first Western third-party developer. In 2013, an FPGA-based clone known as the ZX Uno was announced. All of its hardware, firmware and software are open source, released as Creative Commons licence Share-alike. The use of a Spartan FPGA allows the system to not only re-implement the ZX Spectrum, but many other 8-bit computers and games consoles.
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Common questions
When was the ZX Spectrum officially revealed to journalists?
The ZX Spectrum was officially revealed before journalists by Sinclair at the Churchill Hotel in Marylebone, London on the 23rd of April 1982. Later that week the machine was presented in a blaze of publicity at the Earl's Court Computer Show in London and the ZX Microfair in Manchester.
What were the launch prices for the two ZX Spectrum models released in 1982?
The ZX Spectrum launched with two models including a 16KB basic version priced at £125 and an enhanced 48KB variant priced at £175. The former model had an undercutting price significantly lower than its main competitor the BBC Micro while the latter model's price was comparable to a third of an Apple II computer.
How many units of the ZX Spectrum were sold by the end of its lifespan in 1992?
By the end of the ZX Spectrum's lifespan in 1992 over five million units had been sold making it one of the best-selling British computers of all time. It retained the title of Britain's top-selling computer until the Amstrad PCW surpassed it in the 1990s with eight million units sold by the end of the PCW's lifespan in 1998.
Who designed the hardware for the ZX Spectrum and what memory capacity did it have?
Chief engineer Richard Altwasser was responsible for the ZX Spectrum's hardware design which included a semi-custom uncommitted logic array integrated circuit. The team agreed that the ZX Spectrum must have high-resolution graphics and 16 kilobytes of memory before launching the machine.
When did the Timex Sinclair 2068 enter the market and how did it differ from the original ZX Spectrum?
Sinclair Research granted a licence for the ZX Spectrum design to the Timex Corporation in the United States who introduced an enhanced variant known as the Timex Sinclair 2068. This upgraded model features improvements in sound and graphics but Timex's versions were generally not compatible with Sinclair systems.