TheZX Spectrum (UK:/zɛdɛks/) is an8-bithome computer developed and marketed bySinclair Research. The Spectrum played a pivotal role in thehistory of personal computers andvideo 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 SirClive Sinclair and his small team inCambridge, and was manufactured inDundee, Scotland byTimex Corporation.[5] 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, theZX81.Rick Dickinson designed its distinctive case, rainbow motif, andrubber keyboard. Video output is transmitted to a television set rather than a dedicatedmonitor, whileapplication software is loaded and saved ontocompact audio cassettes.
The ZX Spectrum was initially distributed by mail order, but after severe backlogs it was sold throughHigh Street chains in the United Kingdom. It was released in the US as theTimex Sinclair 2068 in 1983, and in some parts of Europe as theTimex 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-infloppy disk drive in 1987. The machine primarily competed with theCommodore 64,BBC Micro,Dragon 32, and theAmstrad CPC range. Over 24,000 software products were released for the ZX Spectrum.[1]
Its introduction led to a boom in companies producing software andhardware, 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 theAmstrad PCW surpassed it in the 1990s.[6][7][8] It was discontinued in 1992.
The ZX Spectrum was conceived and designed by engineers at Sinclair Research, founded by English entrepreneur and inventorClive Sinclair, who was well known for his eccentricity and pioneering ethic.[9] On 25 July 1961, three years after passing hisA-levels, he foundedSinclair Radionics to advertise his inventions and buy components.[10] In 1972, Sinclair competed withTexas Instruments to produce the world's firstpocket calculator, theSinclair Executive.[11] By the mid 1970s, Sinclair Radionics was producing handheld electronic calculators, miniature televisions, and the ill-fated digitalBlack Watch wristwatch.[12] Due to financial losses, Sinclair sought investors from theNational Enterprise Board (NEB), 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,[13] selling off its television division toBinatone and its calculator division to ESL Bristol.[14]
After incurring a £7 million investment loss, Sinclair was given agolden handshake and an estimated £10,000 severance package.[11][15] 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 theUniversity of Cambridge.[16] By this time inexpensivemicroprocessors had started appearing on the market, which prompted Sinclair to start producing theMK14, acomputer teaching kit which sold well at a very low price.[17] Encouraged by this success, Sinclair renamed his company toSinclair 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.[11] On 29 January 1980, theZX80 home computer was launched to immediate popularity; notable for being one of the first computers available in the United Kingdom for less than £100.[18][19] 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.[20]
On 5 March 1981, theZX81 was launched worldwide to immense success with more than 1.5 million units sold,[21] 60% of which was outside Britain.[22] According toBen 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".[23] 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.[24]
An original concept sketch of the ZX Spectrum, depicting an angular and wedge-like form similar to its predecessor, theZX81
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 6King's Parade, Cambridge.[25] 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.[26] Aside from a newcrystal oscillator and extra chips to add additionalkilobytes of memory,[27] the ZX Spectrum was intended to be, as quoted by Sinclair's marketing manager, essentially a "ZX81 with colour".[25] According to Sinclair, the team also wanted to combine the ZX81's separaterandom-access memory sections for audio and video into a single bank.[28]
Chief engineerRichard Altwasser was responsible for the ZX Spectrum's hardware design. His main contribution was the design of the semi-customuncommitted logic array (ULA) 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 improvedcassette interface, and an impressive colour palette.[29] To achieve this, the team had to divorce thecentral processing unit (CPU) away from the main display to enable it to work at full efficiency – a method which contrasted with the ZX81's integrated CPU.[29] The inclusion of colour proved a major obstacle to the engineers. ATeletext-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 eightbits of memory for each character position; three bits to provide any one of eight foreground colours and three bits for the eightbackground 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.[30]
Much of the firmware was written by computer scientistSteve Vickers from Nine Tiles,[28] who compiled all control routines[clarification needed] to produce theSinclair BASIC interpreter, a custom variant of the general purposeBASIC programming language. Making a custom interpreter made it possible to fit all of its functionality into a very small amount ofread-only memory (ROM).[27] 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.[31]
The distinctive case and colourful design of the ZX Spectrum was the creation ofRick 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.[25] 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.[32]
The design of the Spectrum'srubber keyboard was simplified from several hundred components to a conventional moving keyboard down to "four to five" moving parts using a new technology.[33] 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.[32] Dickinson recalled in 2007 that "everything was cost driven" and that the minimalist,Bauhaus approach to the Spectrum gave it an elegant yet "[non] revolutionary" form.[3] The drawing board on which Dickinson designed the ZX Spectrum is now on display in theScience Museum in London.[34][35]
The need for an improved cassette interface was apparent from ZX81 users who encountered problems trying to save and load programs.[36] To increase the data transfer speed, the team decreased the length of tones that represent binary data.[36] Originally, the team aimed for 1000baud, but succeeded in reaching a considerably faster 1500 baud.[36] To increase reliability, a leading period ofconstant tone was introduced, allowing the cassette recorder'sautomatic gain control to settle down, eliminating hisses on the tape.[36] ASchmitt trigger was added inside the ULA to reduce noise of the received signal.[36] Unlike the ZX81, the Spectrum is able to maintain its display during data transfer, allowing programs to show asplash screen whilst loading.
As with the ZX81, the ZX Spectrum was manufactured inDundee, Scotland, byTimex Corporation at theDryburgh factory.[5][37] 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.[38]
The ZX Spectrum was officially revealed before journalists by Sinclair at theChurchill Hotel inMarylebone, London, on 23 April 1982.[32][39] Later that week, the machine was presented in a "blaze of publicity" at theEarl's Court Computer Show in London,[40][41] and the ZX Microfair inManchester.[42] The ZX Spectrum was launched with two models: a 16KB 'basic' version, and an enhanced 48KB variant.[2] The former model had an undercutting price of £125, significantly lower than its main competitor theBBC Micro, whilst the latter model's price of £175 was comparable to a third of anApple II computer.[43][44] Upon release, the keyboard surprised many users due to its use of rubber keys, described as offering the feel of "dead flesh".[32][45] Sinclair himself remarked that the keyboard's rubber mould was "unusual", but consumers were undeterred.[46]
90 year-oldHarold Macmillan using a ZX Spectrum with Sir Clive Sinclair looking on (1984)
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.[26]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 inWHSmith, which was at the time Sinclair's only retailer.[47] 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.[48] The company's conservative approach to distributing the machine was criticised,[26] with disillusioned customers telephoning and writing letters.[49][50] 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,[32] and promised that the backlog would be cleared by the end of that month.[49] Supply did not return to normal until the 1982 Christmas season.[51]
Production of the machine rapidly increased with the arrival of the less expensive Issue 2motherboard, a redesign of the main circuit board which addressed hardware manufacturing defects that affected production of the first model.[52] Sales of the ZX Spectrum reached 200,000 in its first nine months,[53] rising to 300,000 for the whole of the first year.[54] By August 1983 total sales in Britain and Europe had exceeded 500,000,[55] with the millionth Spectrum manufactured on 9 December 1983. By this point, an average of 50,000 units were being purchased each month.[56]
In July 1983, an enhanced version of the ZX Spectrum was launched in the United States as theTimex Sinclair 2068. Advertisements described it as having 72 kilobytes of memory and a full range of colour and sound for under $200.[57] Despite the improvements upon its British counterpart, sales were poor andTimex Sinclair collapsed the following year.[32][58][59]
A woman is loaned a ZX Spectrum from a library in the Netherlands, 1984.
A crucial part of the company's marketing strategy was to implement regular price-cutting at strategic intervals to maintainmarket share. Ian Adamson and Richard Kennedy noted that Sinclair's method was driven by securing his leading position through "panicking" the competition. While most companies at the time reduced prices of their products while their market share was dwindling, Sinclair Research discounted theirs shortly after sales had peaked, throwing the competition into "utter disarray".[60] Sinclair Research made a profit of £14 million in 1983, compared to £8.5 million the previous year.Turnover doubled from £27.2 million to £54.5 million, which equated to roughly £1 million for each person employed directly by the company.[61]
Clive Sinclair became a focal point during the ZX Spectrum's marketing campaign by putting a human face onto the business. Sinclair Research was portrayed in the media as a "plucky" British challenger taking on the technical and marketing might of giant American and Japanese corporations. As David O'Reilly noted in 1986, "by astute use of public relations, particularly playing up his image of a Briton taking on the world, Sinclair has become the best-known name in micros."[62] The media latched onto Sinclair's image; his "Uncle Clive" persona is said to have been created by the gossip columnist forPersonal Computer World.[63] The press praised Sinclair as a visionary genius, withThe Sun lauding him as "the most prodigious inventor sinceLeonardo da Vinci". Adamson and Kennedy wrote that Sinclair outgrew the role of microcomputer manufacturer and "accepted the mantle of pioneeringboffin leading Britain into a technological utopia".[64] Sinclair's contribution to the technology sector resulted in him beingknighted upon the recommendation ofMargaret Thatcher in theQueen's 1983 Birthday Honours List.[65][66][67]
The United Kingdom was largely immunised from the effects of thevideo game crash of 1983, due to the saturation of home computers such as the ZX Spectrum.[68][69][70] The microcomputer market continued to grow and game development was unhindered despite the turbulence in the American markets. Computer games remained the dominant sector of the British home video game market up until they were surpassed bySega andNintendo consoles in 1991.[71] By the end of 1983 there were more than 450 companies in Britain selling video games on cassette, compared to 95 the year before.[72] An estimated 10,000 to 50,000 people, mostly young men, were developing games out of their homes based on advertisements in popular magazines. The growth of video games during this period has been compared to thepunk subculture, fuelled by young people making money from their games.[73]
By the mid 1980s, Sinclair Research's share of the British home computer market had climbed to a high of 40 per cent.[74] Sales in the 1984 Christmas season were described as "extremely good".[75] In early 1985 the British press reported the home computer boom to have ended,[76] leaving many companies slashing prices of their hardware to anticipate lower sales.[75] Despite this, celebration of Sinclair's success in the computing market continued at theWhich Computer? show inBirmingham, where the five-millionth Sinclair machine (a gold coloured QL) was issued as a prize.[75]
Sinclair shaking hands withAlan Sugar, to mark the conclusion of the sale toAmstrad in 1986
The ZX Spectrum's successor, theSinclair QL, was officially announced on 12 January 1984, shortly before theMacintosh 128K went on sale.[77] Contrasting with its predecessors, the QL was aimed at more serious, professional home users.[78] Fully operational QLs were not available until the late summer, and complaints against Sinclair concerning delays were upheld by theAdvertising Standards Authority (ASA) in May of that year. Particularly serious were allegations that Sinclair was cashing cheques months before machines were shipped. By autumn 1984, Sinclair was still publicly forecasting that it would be a "million seller" and that 250,000 units would be sold by the end of the year.[79] QL production was suspended in February 1985, and the price was halved by the end of the year.[80] It ultimately flopped, with 139,454 units being manufactured.[81]
The ZX Spectrum+, a rebranded ZX Spectrum with identical technical specifications except for the QL-like keyboard, was introduced in October 1984 and made available in WHSmith's stores the day after its launch. Retailers stocked the device in high quantities, anticipating robust Christmas sales. It did not perform as well as projected, leading to a significant drop in Sinclair's income from orders in January, as retailers were left with surplus stock. An upgraded model, the ZX Spectrum 128, was released in Spain in September 1985, financed by the Spanish distributor Investrónica.[82] The UK launch was postponed until January 1986 due to the substantial leftover inventory of the prior model.[83]
While the Sinclair QL was in development, Sinclair also hoped to repeat his success with the Spectrum in the fledgling electric vehicle market, which he saw as ripe for a new approach. On 10 January 1985, Sinclair unveiled theSinclair C5, a small one-personbattery electricrecumbenttricycle. It marked the culmination of Sir Clive's long-running interest in electric vehicles.[84] The C5 turned out to be a significant commercial failure, selling only 17,000 units and losing Sinclair £7 million. It has since been described as "one of the great marketing bombs of postwar British industry".[85] The ASA ordered Sinclair to withdraw advertisements for the C5 after finding that the company's claims about its safety could not be justified.[86]
The combined failures of the C5 and QL caused investors to lose confidence in Sinclair's judgement. In May 1985, Sinclair Research announced their intention to raise an additional £10 to £15 million to restructure the organisation, but securing the funds proved challenging. In June 1985, business magnateRobert Maxwell disclosed a takeover bid for Sinclair Research through Hollis Brothers, a subsidiary of hisPergamon Press.[87] However, the deal was terminated in August 1985.[74] On 7 April 1986 the company sold their entire computer product range, along with the "Sinclair" brand name, toAlan Sugar'sAmstrad for £5 million.[88] The takeover sent ripples through theLondon Stock Exchange, but Amstrad's shares soon recovered, with one stock broker affirming that "the City appears to have taken the news in its stride".[89] Amstrad's acquisition saw the release of three improved ZX Spectrum models throughout the late 1980s.[90]
By 1990, Sinclair Research consisted of Sinclair and two other employees down from 130 employees at its peak in 1985.[91] The ZX Spectrum was officially discontinued in 1992, after ten years on the market.[51][3]
Video output is channelled through anRF modulator, intended for use with contemporary television sets. Text is displayed using a grid of 32 columns × 24 rows of characters from theZX Spectrum character set, or from a custom set. There is a colour palette of 15 colours: seven saturated colours at two levels of brightness and black.[92] Theimage resolution is256 × 192 pixels, subject to the same colour limitations.[93] Colour is stored separately from the pixelbitmap in a32 × 24 grid corresponding to the character cells. This means that all pixels within an8 × 8 character block share one foreground colour and one background colour. Altwasser received a patent for this design.[94]
An "attribute" consists of a foreground and a background colour, a brightness level (normal or bright) and a flashing "flag" which causes the two colours to swap at regular intervals.[93] This scheme leads to what is dubbedattribute clash, where a desired colour of a specific pixel cannot be selected, but only the colour attributes of an8 × 8 block. This became a distinctive feature of the Spectrum, requiring games and other programs to be designed with this limitation in mind. Other machines, such as theAmstrad CPC andCommodore 64, do not suffer from this limitation. While the C64 also uses colour attributes, it has a special multicolour mode and hardwaresprites which do not involve attribute clash.[95]
Sound is produced through a single-channel beeper capable of generating ten octaves.[96] Sounds are generated by toggling a single bit on and off.[97] FromBASIC, theBEEP command plays sounds of specified pitch and duration.[98] The processor is occupied exclusively withBEEP until the sound completes, limiting concurrent operations. Despite these constraints, it was a significant step forward from the silence of theZX81. Programmers devised workarounds and explored unconventional methods such as programming the beeper to emit multiple pitches.[99]
Later software allows for two-channel sound playback. The machine includes anexpansion busedge connector and 3.5 mm audio in/out ports, for connecting acassette recorder to load and save programs and data. TheEAR port has a higher output than theMIC and is recommended for headphones, while theMIC port is intended for attachment to other audio devices as aline-in source.[100]
The machine'sSinclair BASIC interpreter is stored in 16 KiB ROM, along with essential system routines. The ROM code, responsible for tasks such asfloating point calculations andexpression parsing, exhibited significant similarities to ZX81, although a few outdated routines remained in the Spectrum ROM.[101] The Spectrum's keyboard is imprinted with BASIC keywords. To input a command in BASIC, many keywords require a single keyboard stroke. Other keywords require a change of keyboard mode by a few keystrokes.[102]
The BASIC interpreter is derived from the one used on theZX81. A BASIC program for ZX81 can be entered into a ZX Spectrum with minimal modifications. However, Spectrum BASIC introduced numerous additional features, enhancing its usability. TheZX Spectrum character set was expanded compared to that of the ZX81, which lacked lowercase letters. Spectrum BASIC incorporated extra keywords for better graphics and sound functionality, and support for multi-statement lines was added. The built-in ROM tape modulation software routines for cassette data storage enable data transfers at an average speed of 171 bytes per second, with a theoretical peak speed of 256 bytes/s. The tape modulation is significantly more advanced than the ZX81, with approximately four times faster average speeds.[citation needed]
The original ZX Spectrum is remembered for its rubberchiclet keyboard, diminutive size and distinctive rainbow motif. It was originally released on 23 April 1982 with 16 KB of RAM for £125 (equivalent to £557 in 2023) or with 48 KB for £175 (equivalent to £780 in 2023);[104] these prices were reduced to £99 (equivalent to £422 in 2023) and £129 (equivalent to £550 in 2023) respectively in 1983.[105] Owners of the 16 KB model could purchase an internal 32 KB RAM upgrade, which for early "Issue 1" machines consisted of adaughterboard. Later issue machines required the fitting of 8dynamic RAM chips and a fewTTL chips. Users could mail their 16K Spectrums to Sinclair to be upgraded to 48 KB versions. Later revisions contained 64 KB of memory but were configured such that only 48 KB were usable.[106] External 32 KB RAM packs that mounted in the rear expansion slot were available from third parties. Both machines had 16 KB of onboard ROM.[26]
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.[107] Although the official service manual states that approximately 26,000 of these original boards were manufactured,[108] 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.[109] An online tool now exists to allow users to ascertain the likely issue number of their ZX Spectrum by inputting the serial number.[110]
These models experienced numerous changes to its motherboard design throughout its life; mainly to improve manufacturing efficiencies, but also to correct bugs from previous boards. Another issue was with the Spectrum's power supply. In March 1983, Sinclair issued an urgent recall warning for all owners of models bought after 1 January 1983.[111] Plugs with a non-textured surface were at risk of causing shock, and were asked to be sent back to a warehouse inCambridgeshire which would supply a replacement within 48 hours.[111][112]
Development of theZX Spectrum+ began in June 1984,[113] and was released on 15 October that year at £179.[114][115][116] It was assembled by AB Electronics inSouth Wales andSamsung in South Korea.[117] This 48 KB Spectrum introduced a newQL-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,[113] however, some retailers reported a failure rate of up to 30%, compared with a more typical 5–6% for the older model.[116] In early 1985, the original Spectrum was officially discontinued, and the ZX Spectrum+ was reduced in price to £129.[75]
In 1985, Sinclair developed the ZX Spectrum 128 (codenamedDerby) in conjunction with their Spanish distributor Investrónica (a subsidiary ofEl Corte Inglés department store group).[118][119][120] Investrónica had helped adapt the ZX Spectrum+ to the Spanish market after their government introduced a special tax on all computers with 64 KB RAM or less,[121] and a law which obliged all computers sold in Spain to support the Spanish alphabet and show messages in Spanish.[122]
The appearance of the ZX Spectrum 128 is similar to the ZX Spectrum+, with the addition of a large externalheatsink for the internal 7805voltage regulator to the right-hand end of the case, replacing the internal heatsink in previous versions. This externalheatsink led to the system's nickname, "TheToast Rack".[123] New features included 128 KB RAM with RAM disc commands, three-channel audio via theAY-3-8912 chip,MIDI compatibility, anRS-232 serial port, anRGB monitor port, 32 KB of ROM including an improved BASIC editor, and an external keypad.[99]
The machine was simultaneously unveiled for the first time and launched in September 1985 at theSIMO '85 trade show in Spain, with a price of 44,250pesetas. Sinclair later presented the ZX Spectrum 128 atThe May Fair Hotel's Crystal Rooms in London, where he acknowledged that entertainment was the most common use of home computers. Due to the large number of unsold Spectrum+ models, Sinclair decided not to start it selling in the United Kingdom until January 1986 at a price of £179.[124][70]
TheZilog Z80 processor used in the Spectrum has a16-bit address bus, which means only 64 KB of memory can be directly addressed. To facilitate the extra 80 KB of RAM the designers usedbank switching so the new memory would be available as eight pages of 16 KB at the top of the address space. The same technique was used to page between the new 16 KB editor ROM and the original 16 KB BASIC ROM at the bottom of the address space.[125]
The new sound chip andMIDI out abilities were exposed to the BASIC programming language with the commandPLAY and a new commandSPECTRUM was added to switch the machine into 48K mode, keeping the current BASIC program intact (although there is no command to switch back to 128K mode). To enable BASIC programmers to access the additional memory, a RAM disk was created where files could be stored in the additional 80 KB of RAM. The new commands took the place of two existing user-defined-character spaces causing compatibility problems with certain BASIC programs.[126] Unlike its predecessors, it has no internal speaker, and can only produce sound from a television speaker.[127]
The new keyboard does not have the BASIC keyword markings of earlier Spectrums, except forLOAD,CODE, andRUN markings. Instead, the +2 has a menu system, almost identical to that of the ZX Spectrum 128, allowing users to switch between 48K BASIC programming with keywords and 128K BASIC programming, where all words, both keywords and others, need to be typed out in full. Despite these changes, the layout remained identical to that of the 128.[117]
The ZX Spectrum +3, launched in 1987, replaces replaces the cassette drive with a built-in 3-inchfloppy disk. Initially £249,[128] it later retailed for £199.[129] It is the only Spectrum model capable of running theCP/M operating system without additional hardware. Unlike its predecessors, the ZX Spectrum +3 power supply uses a DIN connector.[130]
Significant alterations caused a series of incompatibilities. The removal of several lines on the expansion bus edge connector caused complications for some peripherals. Additionally, changes in memory timing led to certain RAM banks being contended, causing failures in high-speed colour-changing effects. The keypad scanning routines from the ROM were also eliminated, so some older 48K and 128K games no longer worked. The ZX Interface 1 was also incompatible because of disparities in ROM and expansion connectors, making it impossible to connect and use the Microdrive units.[117]
Production of the +3 was discontinued in December 1990, reportedly in response to Amstrad's relaunch of their CPC range, with an estimated 15% of ZX Spectrums sold being +3 models at the time. The +2B model, the only other model still in production at this point, continued to be manufactured, as it was believed not to be in direct competition with other computers in Amstrad's product range.[131][132]
The ZX Spectrum +2A was a new version of the Spectrum +2[133] using the same circuit board as the Spectrum +3.[133][134] It was sold from late 1988 and unlike the original grey +2 is housed in a black case.[133][134] The Spectrum +2A/+3 motherboard (AMSTRAD part number Z70830) was designed so that it could be assembled with a +2 style "datacorder" connected instead of thefloppy disk controller.[135] The power supply of the ZX Spectrum +2A uses the samepinout as the +3.[136]
The ZX Spectrum +2B and ZX Spectrum +3B were released in 1989. They are functionally similar in design to the Spectrum +2A and +3,[137] though changes to the generation of the audio output signal were made to resolve problems withclipping.[138] The +2B board has no provision for floppy disk controller circuitry, while the +3B motherboard has no provision for connecting an internal tape drive. Production of all Amstrad Spectrum models ended in 1992.[3]
Sinclair Research granted a licence for the ZX Spectrum design to theTimex Corporation in the United States. Timex marketed several computer models under theTimex Sinclair brand. They introduced an enhanced variant of the original Spectrum in the US, known as theTimex 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 Computer 2048, highly compatible with the ZX Spectrum 48K, was very successful in both Portugal and Poland.
Timex of Portugal developed and produced several branded computers, including aPAL region-compatible version of the Timex Sinclair 2068, known as theTimex 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.[139][140] Software developed for the Portuguese-made 2048 remained fully compatible with its American counterpart, as the ROMs were left unaltered. Timex of Portugal also created a ZX Spectrum "emulator" in cartridge form.[141] Several other upgrades were introduced, including a BASIC64 cartridge enabling it to utilise high-resolution (512x192) modes.[142] This model saw significant success in both Portugal and Poland.[143]
TheSAM Coupé, despite being a commercial failure, is hailed as a credible successor to the ZX Spectrum.
In India, Deci Bells Electronics Limited[144] based inPune, introduced a licensed version of the Spectrum+ in 1988.[145][146][147] Dubbed the "dB Spectrum+", it performed well in the Indian market, selling over 50,000 units and achieving an 80% market share.[148]
Numerousunofficial Spectrum clones were produced, especially in Eastern Europe. Many small start-ups in theSoviet Union assembled various clones, distributed through poster adverts and street stalls. Over 50 such clone models existed in total.[149] InCzechoslovakia, the first production ZX Spectrum clone was theDidaktik Gama, sporting twoswitched 32 KB memory banks and 16 KB of slower RAM containing graphical data for video output, followed byDidaktik M, with later availability of a 5.25"/3.5"floppy disk drives; and aDidaktik Kompakt clone with a built-in floppy drive.[150] There were also clones produced in South America, such as the Brazilian-madeTK90X andTK95,[151] as well as the ArgentineCzerweny CZ models.[152]
In the United Kingdom, Spectrum peripheral vendorMiles Gordon Technology (MGT) released theSAM Coupé 8-bit home computer in December 1989. It was designed to be fully compatible with the ZX Spectrum 48K, housing a Zilog Z80B processor clocked at 6 MHz and 256KB of RAM.[153] By this point, theAmiga andAtari ST had taken hold of the market, leaving MGT in eventual receivership in June 1990.[154] In his bookRetro Tech,Peter Leigh considers the Sam Coupé to be the "true" successor of the ZX Spectrum.[155]
Severalperipherals were developed and marketed by Sinclair. TheZX Printer, a smallspark printer, was already on the market upon the ZX Spectrum's release,[156] as itscomputer bus was partiallybackward-compatible with that of its predecessor, the ZX81. It uses two electrically charged styli to burn away the surface of aluminium-coated paper to reveal the black underlay.[157]
TheZX Interface 1 add-on module, launched in 1983, includes 8 KB of ROM, anRS-232 serial port, a proprietarylocal area network (LAN) interface known as ZX Net, and a port for connecting up to eightZX Microdrives – tape-loop cartridge storage devices released in July 1983, known for their speed, albeit with some reliability concerns.[158][159] Sinclair Research also introduced theZX Interface 2, which added two joystick ports and aROM cartridge port.[160] Although the ZX Microdrives were initially greeted with good reviews,[161] they never became a popular distribution method due to fears over cartridge quality and piracy.[162]
Third-party hardware add-ons were available throughout the machine's life, including theKempston joystick interface,[163] the Morex PeripheralsCentronics/RS-232 interface, theCurrah Microspeech unit for speech synthesis,[164]Videoface Digitiser,[165] theSpecDrum drum machine,[166] and theMultiface, a snapshot and disassembly tool from Romantic Robot.[167] After the original ZX Spectrum's keyboard received criticism for its "dead flesh" feel,[3] external keyboards became popular.[168] In 1983, DK'Tronics launched a Light Pen compatible with some drawing software.[169]
The Abbeydale Designers/Watford Electronics SPDOS and KDOS disk drive interfaces were bundled with office productivity software, including theTasword word processor, Masterfile database, andOmnicalc spreadsheet.[170] This bundle, along with OCP's Stock Control, Finance, and Payroll systems, introduced small businesses to streamlined computerised operations.[51] In 1987 and 1988,Miles Gordon Technology released theDISCiPLE and+D systems. These systems had the capability to store memory images as disk snapshots, allowing users to restore the Spectrum to its exact previous state. Both systems were compatible with the Microdrive command syntax, simplifying the porting of existing software.[171]
In the mid-1980s, Telemap Group launched a fee-based service allowing ZX Spectrum users to connect their machines to theMicronet 800 information provider via a Prism Micro Products VTX5000 modem. Micronet 800, hosted byPrestel, provided news and information about microcomputers and offered a form of instant messaging and online shopping.[172]
Most Spectrum software was originally distributed onaudio cassette tapes, intended to work with consumer cassette recorders.[26][173] Software was also distributed throughtype-in program listings in magazines and books.[2][174][175] The reader entered a program by hand and saved it to cassette for later use. Some magazines distributed 7" 331⁄3 rpmflexi disc records, or "Floppy ROMs", a variant of regularvinyl records which could be played on a standard record player.[176] Some radio stations broadcast audio stream data viafrequency modulation ormedium 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.[177]
Initial reception of the ZX Spectrum was generally positive. Critics in Britain welcomed the new machine as a worthy successor to theZX81; Robin Bradbeer ofSinclair User praised the additional keyboard functions the Spectrum had to offer, and lauded the "strength" of its ergonomic and presentable design.[191]Tim Hartnell fromYour Computer noted that Sinclair had improved on the shortcomings of theZX80 and ZX81 by revamping the Spectrum's load and save functions, noting that it made working with the machine "a pleasure".[192] Hartnell concluded that despite minor faults, the machine was "way ahead" of its competitors, and its specification exceeded that of theBBC Micro Model A.[193]
Computer and Video Games' Terry Pratt compared the Spectrum's keyboard negatively to the typewriter-style used on the BBC Micro, opining that it was an improvement over the ZX81 but unsuited for "typists".[194] In similar vein, David Tebbutt fromPersonal Computer World felt that the Spectrum's keyboard felt more like a calculator than typewriter, but praised its functional versatility.[195] Likewise, Gregg Williams fromBYTE criticised the keyboard, declaring that despite the machine's attractive price the layout "is impossible to justify" and "poorly designed" in several respects. Williams was sceptical of the computer's appeal to American consumers if sold forUS$220 – "hardly competitive with comparable low-cost American units" – and expected that Timex would sell it for$125–150.[196] A more negative review came from Jim Lennox ofTechnology Week, who wrote that "after using it [...] I find Sinclair's claim that it is the most powerful computer under £500 unsustainable. Compared to more powerful machines, it is slow, its colour graphics are disappointing, its BASIC limited and its keyboard confusing".[70]
"You cannot exaggerate SirClive Sinclair’s influence on the world [...] All your UK video game companies today were built on the shoulders of giants who made games for the ZX Spectrum."
The role of the ZX Spectrum in thehistory of personal computers andvideo games made it one of the most important and influential computers of the 1980s.[2][3][198] Some observers credit it as being responsible for launching the British information technology industry duringa period of recession,[199] while introducing home computing to the masses.[200] As of 2024[update], it is also one of the best-selling British computers of all time, with over five million units sold by the end of the Spectrum's lifespan in 1992.[6][8] It retained the title of Britain's top-selling computer until theAmstrad PCW surpassed it in the 1990s, with eight million units sold by the end of the PCW's lifespan in 1998.[7][8] The ZX Spectrum is affectionately known as the "Speccy" by elements of its fan following.[201]
The ZX Spectrum was popular in communistCzechoslovakia, 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.[202]
Some hobbyists have continued to code for the Spectrum via emulators.[207] Several games have been released commercially from new software houses such asCronosoft.[208] In 2020, a museum dedicated Sinclair computers opened inCantanhede, Portugal.[209]
In 2013, anFPGA-basedclone known as theZX Uno, was announced. All of its hardware, firmware and software areopen source,[210] released asCreative Commons licence Share-alike. The use of aSpartan FPGA allows the system to not only re-implement the ZX Spectrum, but many other 8-bit computers and games consoles.[211] The Uno was successfullycrowdfunded in 2016 and the first boards went on sale the same year.[212]
In January 2014,Elite Systems, who produced a successful range of software for the original ZX Spectrum in the 1980s, announced plans for a Spectrum-themedBluetooth keyboard that would attach to mobile devices.[213][214] The company used a crowdfunding campaign to fund theRecreated ZX Spectrum, which would be compatible with games the company had already released oniTunes andGoogle Play.[215] Elite Systems took down its Spectrum Collection application the following month, due to complaints from authors of the original software that they had not been paid for the content.[216]Wired UK described the finished device, which was styled as an original Spectrum 48k keyboard, as "absolutely gorgeous" but said it was ultimately more of an expensive novelty than an actual Spectrum.[217] In July 2019,Eurogamer reported that many of the orders had yet to be delivered due to a dispute between Elite Systems and their manufacturer, Eurotech.[218]
The ZX Spectrum Vega TV Game Console, made by Retro Computers
Later in 2014, theZX Spectrum Vega retro video game console was announced by Retro Computers and crowdfunded onIndiegogo with the backing of Clive Sinclair.[219] The Vega, released in 2015, took the form of ahandheld TV game[219][220] but the lack of a full keyboard[46] led to criticism from reviewers due to the large number of text adventures supplied with the device.[221][222] Most reviewers branded the device cheap and uncomfortable to use.[223][217] The follow-up, theZX Spectrum Vega+, was designed as ahandheld game console. Despite reaching its crowdfunding target in March 2016,[224] the company failed to fulfil the majority of orders. Reviewing the Vega+,The Register criticised numerous aspects and features of the machine, including its design and build quality and summed up by saying that the "entire feel is plasticky and inconsequential".[225] Retro Computers Ltd was placed into liquidation in 2019.[226]
TheZX Spectrum Next is an expanded and updated version of the ZX Spectrum computer implemented with FPGA technology[227] funded by aKickstarter campaign in April 2017,[228] with the board-only computer delivered to backers later that year.[229] The finished machine, including a case designed byRick Dickinson who died during the development of the project,[230][user-generated source?] was released to backers in February 2020.[231]MagPi called it "a lovely piece of kit", noting that it is "well-designed and well-built: authentic to the original, and with technology that nods to the past while remaining functional and relevant in the modern age".[232]PC Pro magazine called the Next "undeniably impressive" while noting that some features were "not quite ready".[233] A further Kickstarter for an improved revision of the hardware was funded in August 2020.[234]
TheZX Touch is a handheld gaming console, released by Elmar Electronic in November 2023, that usesbare-metal emulation to play ZX Spectrum games. It features a 7-inch touchscreen, built-in games, and microSD support for loading additional games.[235]
In August 2024, Retro Games announced that they would be releasing a recreation of the ZX Spectrum titled "The Spectrum" which would include 48 built-in games, a save game option, rewind mode and pre-owned titles load up. It was released on 22 November 2024.[236][237]
A running gag in the filmScott Pilgrim vs. the World has characterJulie Powers censored with ZX Spectrum sound effects. DirectorEdgar Wright stated that he used to wait for Spectrum games to load when he was a teenager.[238]
One of the alternate endings in theinteractive filmBlack Mirror: Bandersnatch (2018) includes the main character playing data tape audio that, when loaded into a ZX Spectrum emulator, generates aQR code leading to a website with a playable version of the "Nohzdyve" game from the film.[240]
^Warman, Matt (23 April 2012)."ZX Spectrum at 30: the computer that started a revolution".The Daily Telegraph. London.Archived from the original on 8 March 2013. Retrieved31 March 2015.It was the computer that introduced a generation to video gaming, helped to earn Sir Clive Sinclair a knighthood and even made programming cool: the ZX Spectrum has a lot to answer for.
^Goodwin, Simon (September 1984)."Suddenly, it's the 64K Spectrum!".Your Spectrum (7):33–34.Archived from the original on 22 May 2014. Retrieved31 March 2015.So the first three issues of the Spectrum used a combination of eight 16K chips and eight 32K ones. The latest machines depart from that combination, but Sinclair Research has been very quiet about the alteration.
^Owen, Chris (6 September 2003)."Spectrum 48K Versions".Planet Sinclair.Archived from the original on 21 March 2015. Retrieved31 March 2015.It is often possible to determine which version of the Spectrum 16/48K one has without opening the case, as there are a number of clues...
^Thorn (EMI) Datatech Ltd (March 1984).Servicing Manual For ZX Spectrum(PDF). Sinclair Research Ltd. p. 4.3.Archived(PDF) from the original on 1 February 2019. Retrieved31 January 2019.
^"ZX Spectrum Models".Spectrum for Everyone.Archived from the original on 9 September 2021. Retrieved9 September 2021.
^"Spectrum surprise!".Home Computing Weekly. No. 85. Argus Specialist Publications. 23 October 1984. p. 1. Archived fromthe original on 24 September 2020. Retrieved23 May 2021.
^abOwen, Chris."ZX Spectrum+".Planet Sinclair.Archived from the original on 3 September 2011. Retrieved21 August 2006.
^ab"Amstrad again".New Computer Express. No. 5. Future Publishing. 10 December 1988. p. 55. Archived fromthe original on 8 August 2020. Retrieved26 November 2022.
^"Spex – Sounding Out".New Computer Express. No. 44. Future Publishing. 9 September 1989. p. 54. Archived fromthe original on 15 June 2024. Retrieved26 November 2022.
^Zangoni, Néstor (7 January 2005)."CZERWENY Series (CZ) Argentina (Z80A)".MicroHobby Web independiente para usuarios de ordenadores Sinclair y compatibles (in Spanish).Archived from the original on 5 April 2024. Retrieved16 January 2023.
^Williams, Chris (23 April 2007)."Sinclair ZX Spectrum: 25 today".The Register. London: Situation Publishing.Archived from the original on 18 July 2018. Retrieved14 September 2008.
^Corfield, Gareth (5 February 2019)."Is this a wind-up?".The Register. Situation Publishing.Archived from the original on 5 February 2019. Retrieved5 February 2019.
^"About".Sinclair ZX Spectrum Next. 29 April 2017.Archived from the original on 5 November 2023. Retrieved13 February 2020.
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