ZX Spectrum

From Academic Kids

The Sinclair ZX Spectrum was a small home computer released in the United Kingdom in 1982 by Sinclair Research. Based on a Zilog Z80 CPU running at 3.50 MHz, the Spectrum came with either 16 KB or 48 KB of RAM (an expansion pack was also available to upgrade the former). The hardware designer was Richard Altwasser of Sinclair Research and the software was written by Steve Vickers (on contract from Nine Tiles Ltd, the authors of Sinclair BASIC). Sinclair's industrial designer Rick Dickinson was responsible for the machine's outward appearance. Originally dubbed the ZX82, the machine was later renamed the "Spectrum" by Sinclair to highlight the machine's colour display, compared to the black-and-white of its predecessors the ZX80 and ZX81.

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The original 1982 ZX Spectrum.



Video output was to a TV, for a simple colour graphic display. The rubber keyboard (on top of a membrane, similar to calculator keys) was marked with Sinclair BASIC keywords, so that pressing, say, "G" when in programming mode would insert the BASIC command GOTO. Programs and data were stored using a normal cassette recorder.

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ZX Spectrum rubber keyboard

The Spectrum's video display, although rudimentary by today's standards, was perfect at the time for display on portable TV sets, and didn't present much of a barrier to game development. The text mode display was 32 columns × 24 rows of characters from the Spectrum Character Set, with a choice of 8 colours in either normal or bright mode, which gave 15 shades (black was the same in both modes). The graphics resolution was 256×192 with the same colour limitations. The Spectrum had an interesting method of handling colour; the colour attributes were held in a 32×24 grid, separate from the text or graphical data, but was still limited to only two colours in any given character cell. This led to what was called colour clash or attribute clash with some bizarre effects in arcade style games. This problem became a distinctive feature of the Spectrum and an in-joke among Spectrum users, as well as a point of derision by advocates of other systems. Other machines available around the same time (for example the Commodore 64 and Amstrad CPC) did not suffer from this problem.

The Spectrum was the first mainstream audience home computer in the UK, similar in significance to the Commodore 64 in the USA (the C64 also being the main rival to the Spectrum in the UK market). An enhanced version of the Spectrum with better sound, graphics and other modifications was marketed in the USA by Timex as the TS2068.


ZX Spectrum (1982)

Released by Sinclair in 1982 and available with either 16 KB (£125, later £99) or 48 KB (£175, later £129) of RAM and 16 KB ROM. Remembered for its rubber keyboard and diminutive size. Owners of the 16 K model could purchase an external 32K RAMpack that mounted in the rear expansion slot. Also available was an internal 32K RAM update, which consists of 8 dynamic RAMs and few TTL chips. As with the ZX81, "RAMpack wobble" caused by poor connection with the expansion was the bane of many users, causing instant crashes and sometimes ULA or CPU burnout.

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ZX Spectrum+ with third-party joystick interface installed.

ZX Spectrum+ (1984)

The 48K Spectrum gets a much needed solid keyboard and reset button, retailing for £180. An upgrade package for older machines was also available. Most hard core users (programmers and gamers) dislike the new keyboard. But the new style helps the Spectrum to look less like a toy and more like a computer.

ZX Spectrum 128K (1986)

The last Spectrum to be produced by Sinclair (developed in Cambridge but initially launched in Spain due to a deal with the Spanish Sinclair distributor Investronica) and based on the Spectrum+. New features included three-channel audio via the AY-3-8912 chip, MIDI compatibility, 128 KB RAM, an RS-232 serial port and an RGB monitor output.

The 128K model saw a second 16 KB ROM chip (Derby ROM) hosting the new 128K editor and enhancements with both ROMs and additional RAM using bank switching techniques to bypass the 64 KB memory limit of the Z80 processor.

ZX Spectrum +2 (1986)

Shortly after Amstrad's buyout of Sinclair Research in 1986 came the ZX Spectrum +2. It featured a new casing coloured grey, distinguishing itself from the familiar black of previous Spectrums. The new case also integrated a new spring loaded keyboard, dual joystick ports, and a built-in cassette recorder dubbed the "Datacorder" (like the Amstrad CPC 464). Production cost cutting saw the retail price drop to £139-£149. Aside from the tape drive, revised keyboard and casing the +2 was essentially the same as the 128 model.

ZX Spectrum +3 (1987)

Amstrad produced disk version based on the +2 but featuring a built-in 3-inch floppy disk drive (like the Amstrad CPC 6128). Most models featured distorted sound thanks to a design fault later rectified in the "4.1 ROM" model. This machine retailed for £249 then later £199 and the only model capable of running CP/M without additional hardware.

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Power-on menu on Spectrum +3.

The +3 saw the addition of two more 16K ROMs, now physically implemented as two 32K chips, one home to the second part of the reorganised 128K ROM, the other hosting the +3's disk operating system.

Such core changes brought incompatibilities:

  • Removal of lines on the edge connector - Caused many external devices problems, some such as the VTX5000 model could be used via a FixIt device
  • Reading a non-existent IO port no longer returned the last attribute - Caused some games such as Sabre Wulf to be unplayable
  • Memory timings - Some of the RAM banks were now contended causing high-speed colour-changing effects to fail

ZX Spectrum +2A / +2B (1987)

The +2A was produced to homogenize Amstrad's range. Although the case reads "ZX Spectrum +2", the +2A/B is easily distinguishable from the original +2 as the case was restored to the standard Spectrum black.

The +2A was derived from Amstrad's +3 4.1 ROM model, hosting a new motherboard which vastly reduced the chip count, integrating many of them into a new ASIC. The +2A replaced the +3's disk drive and associated hardware with a tape drive, as in the original +2. Originally, Amstrad planned to introduce an additional disk interface, but this never appeared.

The only differences between the +2A and +2B was a move in manufacturing from Hong Kong to Taiwan and that the ROM was upgraded to version 4.1 in the +2B.


Sinclair licensed the Spectrum design to Timex in the USA who produced their own, largely incompatible, derivatives. However, some of the Timex innovations were later adopted by Sinclair Research. A case in point was the abortive 'Pandora' portable Spectrum, whose ULA had the high resolution video mode pioneered in the TS2068. 'Pandora' had a flat-screen TV monitor and Microdrives and was intended to be Sinclair's business portable - after Alan Sugar bought the computer side of Sinclair, he took one look at it and ditched it (a conversation between him and UK computer hack Guy Kewney went thusly: GK:"Are you going to do anything with Pandora?" AS:"Have you seen it?" GK:"Yes" AS:"Well then.").

In the UK Spectrum peripheral vendor Miles Gordon Technology (MGT) released the SAM Coupé as the natural successor with some Spectrum compatibility however the Commodore Amiga and Atari ST had taken hold of the market by this point leaving MGT in eventual receivership.

Many unofficial Spectrum clones were produced, especially in Eastern Europe and South America. Some of them are still being produced such as the Sprinter from Peters Plus Ltd (http://www.eng.petersplus.ru/). Russian clones include the Hobbit, Pentagon and Scorpion. Brazilian clones include TK 90X and TK-95 from Microdigital.


Several peripherals for the Spectrum were marketed by Sinclair: the printer was already on the market, as the Spectrum had retained the protocol for the ZX81's printer. The Interface 1 added a standard RS-232 serial port, a proprietary format local area networking port, and the ability to connect up to eight ZX Microdrives – somewhat unreliable but speedy tape-loop storage devices (later used in a revised version on the Sinclair QL, whose storage format was electrically compatible but logically incompatible with the Spectrum's). Sinclair also released the Interface 2 which added two joystick ports and a ROM cartridge port.

There were also a plethora of third-party hardware addons. The more well-known of these included the Kempston joystick interface, the Currah Microspeech unit (speech synthesis), and the Multiface (snapshot and disassembly tool), from Romantic Robot. There were numerous disk drive interfaces, including the Opus Discovery and the DISCiPLE/PlusD from Miles Gordon Technology. During the mid-80s, the company Micronet800 launched a service allowing users to connect their ZX Spectrums to a network known as Prestel. This service had some similarities to the Internet, but was proprietary and fee-based.


The Spectrum family enjoyed a very large software library of at least 20,000 titles. Despite the fact that the Spectrum hardware was limited by most standards, its software library was very diverse, including programming language implementations (C, Pascal, Prolog, Forth, several Z80 assemblers/disassemblers (eg: Devpac, ZEUS, Artic Assembler), Sinclair BASIC compilers (eg: MCoder, COLT), Sinclair BASIC extensions (eg: Beta Basic, Mega Basic), databases (eg: VU-File), word processors (eg: Tasword II), spread sheets (eg: VU-Calc). drawing and painting tools (eg: Art Studio, Artist, Paintbox, Melbourne Draw), and, of course, many, many games.

A number of current leading games developers and development companies began their careers on the ZX Spectrum, including Peter Molyneux (ex-Bullfrog Games), Dave Perry of Shiny Entertainment, and Ultimate Play The Game (now known as Rare, maker of many famous titles for Nintendo game consoles). Other prominent games developers include Matthew Smith (Manic Miner, Jet Set Willy), and Jon Ritman (Match Day, Head Over Heels).

Most Spectrum software was originally distributed on audio cassette tapes. The software was encoded on tape as a sequence of alternating pitches, similar to the sounds of a modern day modem. Standard speed was 1500 baud (in this case 1 baud = 1 bit per second) but higher speeds were possible using custom machine code loaders instead of the ROM routines. Complex loaders with unusual speeds or encoding were the basis of the ZX Spectrum copy prevention schemas, although other methods were used including asking for a particular word from the documentation included with the game - often a novella - or the notorious Lenslok system. This had a set of plastic prisms in a fold-out red plastic holder: the idea was that a scrambled word would appear on the screen, which could only be read by holding the prisms at a fixed distance from the screen courtesy of the plastic holder. This relied rather too much on everyone using the same size television, and Lenslok became a running joke with Spectrum users.

A standard 48 K program would take about 4.5 minutes (49152 bytes * 8 = 393216 bits; 393216 bits / 1500 baud = 262.14 seconds = 4.36 minutes) to load. Curiously, experienced users could tell the type of a file, e.g. machine code, BASIC program, or screen image, from the way it sounded on the tape.

One very interesting kind of software was copiers. Most were piracy oriented, and their function was only tape duplication, but when Sinclair Research launched the ZX Microdrive (later with a diskette system), copiers were developed to copy programs from audio tape to microdrive tapes or diskettes. Best known were the LERM copiers produced by Lerm Software, Omni Copy 2, and others. As the protections became more complex (e.g. Speedlock 1-8) it was almost impossible to use copiers to copy tapes, and the loaders had to be cracked by hand, and unprotected versions produced. This was, of course, illegal, but in the 1980s most of South and Eastern Europe didn't have software copyright laws.

The Spectrum was intended to work with almost any cassette tape player, and despite differences in audio reproduction fidelity, the software loading process was quite reliable; however all the Spectrum users know and dread the "R Tape loading error, 0:1" message.

Typical settings for loading were 3/4 volume, 100% treble, 0% bass. Audio filters like loudness and Dolby Noise Reduction had to be disabled, and it was not recommended to use a Hi-Fi player to load programs. There were some tape recorders build specially for digital use, such as the Timex Computer 2010 Tape Recorder (Portugal).

In addition to tapes, software was also distributed through print media, fan magazines, or books. The prevalent language for distribution was the Spectrum's BASIC dialect ZX BASIC. The reader would type the software into the computer by hand, run it, and save it on tape for later use. The software distributed in this way was in general simpler and slower than its assembly language counterparts, and lacked graphics, but soon, magazines were printing long lists of checksumed hexadecimal digits with machine code games or tools. There was a vibrant scientific community built around such software, ranging from satellite dish alignment programs to school classroom scheduling programs.

One unusual software distribution methods was a radio show (in Eastern Europe) where the host would describe a program, instruct the audience to connect a cassette tape recorder to the radio, and then broadcast the program over the airwaves in audio format.

Other unusual method were 33⅓ rpm floppy or soft disks (not the hard vinyl ones) that were played on a standard hifi pickup of a record player. These disks were known as "floppy ROMs,". This method was used in France by some magazines. See: "Unusual types of gramophone record#Unusual materials".

A few pop musicians included Sinclair programs on their records. Ex-Buzzcock Peter Shelly put a Spectrum program including lyrics and other information as the last track on his XL-1 album. Festival favourites Hawkwind put a Spectrum database of band information on their 1984 release, 'New Anatomy'. Also in 1984, the Thompson Twins released an extraordinarily bad game on vinyl. The Freshies had a brief flirtation with fame and Spectrum games, and the Aphex Twin included various loading noises on his Richard D. James album in 1996 - most notably the loading screen from SabreWulf on Corn Mouth.

As audio tapes have a limited shelf-life, most Spectrum software has been digitized in recent years and is available for download in digital form. One popular program for digitizing Spectrum software is Taper (http://www.worldofspectrum.org/taper.html): it allows connecting a cassette tape player to the line in port of a sound card or (through a simple home-built device) to the parallel port of a PC. Once in digital form, the software can be executed on one of many existing emulators (http://www.worldofspectrum.org/emulators.html), on virtually any platform available today. Today, the largest on-line archive of ZX Spectrum software is The World of Spectrum (http://www.worldofspectrum.org) site with more than 12,000 titles.

The Spectrum enjoys a vibrant, dedicated fan-base. Since it was cheap and simple to learn to use and program, the Spectrum was the starting point for many programmers and technophiles who remember it with nostalgia. The hardware limitations of the Spectrum imposed a special level of creativity on game designers, and for this reason, many Spectrum games are very creative and playable even by today's standards.

Best Of


Your Sinclair Top 10

Between July and November 1991 Your Sinclair published a list of what they considered to be the top 100 games for the ZX Spectrum. Their top 10 were:

  1. 3d Deathchase
  2. Rebelstar
  3. All or Nothing
  4. Stop the Express
  5. Head over Heels
  6. R-Type
  7. The Sentinel
  8. Rainbow Islands
  9. Boulder Dash
  10. Tornado Low Level
Crash! Top 10

Between August and December 1991 Crash! published their list of the top 100 ZX Spectrum games, including in the top 10:

  1. Rainbow Islands
  2. Chase HQ
  3. Robocop
  4. Robocop 2
  5. Dizzy
  6. Target: Renegade
  7. Magicland Dizzy
  8. Batman - The Movie
  9. Operation Wolf
  10. Midnight Resistance

Of these all but the Dizzy games were published by Ocean Software.

Wikipedian's Picks
</table> </table> See also: World of Spectrum top 100 (http://www.worldofspectrum.org/bestgames.html)


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Head over Heels

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Jet Set Willy - Main

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Jet Set Willy - Banyan Tree

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Jet Set Willy - Kitchen

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Sabre Wulf

Head Over Heels Jet Set Willy Sabre Wulf
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Highway Encounter

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Highway Encounter

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The Sentinel

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The Sentinel

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The Sentinel

Highway Encounter The Sentinel Match Point
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Screenshot from "3 Weeks in Paradise"

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Screenshot from "Chuckie Egg"

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Screenshot from "Elite"

3 Weeks in Paradise Chuckie Egg Elite
Mikrogen (1985) A&F (1984) Firebird (1985)
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Screenshot from "Jet Set Willy"

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Screenshot from "Knight Lore"

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Screenshot from "Saboteur"

Jet Set Willy Knight Lore Saboteur
Software Projects (1984) Ultimate (1984) Durell (1987)


  • CPU
    • Zilog Z80A CPU, 3.50 MHz (Spectrum 16K, 48K, +) or 3.54 MHz (Spectrum 128K and later)
  • Read-only memory ROM
    • 16 KB ROM (BASIC: Spectrum 48K, +)
    • 32 KB ROM (BASIC, Editor: Spectrum 128K, +2)
    • 64 KB ROM (BASIC, Editor, Syntax check, DOS: Spectrum +3, +2A, +2B)
  • Random-access memory RAM
    • 16 KB RAM (Spectrum 16K)
    • 48 KB RAM (Spectrum 48K, +)
    • 128 KB RAM (Spectrum 128K, +2, +3, +2A, +2B)
  • Display
    • Text: 32×24 characters
    • Graphics: 256×192 pixels, 15 colours (two simultaneous colours per 8×8 pixels)
  • Sound
    • Beeper (1 channel, 5 octaves: Spectrum 16/48 via internal speaker, others via TV)
    • AY-3-8912 chip (3 channels, 7 octaves: Spectrum 128, +2, +2A, +3)
  • I/O
    • Z80 bus in/out
    • Tape audio in/out (all except Spectrum +2)
    • RF television out
    • RS-232 in/out (Spectrum 128, +2, +2A, +3)
    • MIDI out (Spectrum 128, +2, +2A, +3)
    • RGB monitor out (Spectrum 128, +2, +2A, +3)
    • Joystick inputs, 2 (Spectrum +2, +2A, +3)
    • External numeric keypad (Spectrum 128 in Spain only)
  • Storage

See also

External links

Sinclair computers, derivatives, and clones (ZX80/81, ZX Spectrum, and QL clones)

By Sinclair Research and AmstradZX80 | ZX81 | ZX Spectrum, Spectrum+, Spectrum 128, +2 and +3 (the latter two by Amstrad) | Sinclair QL
By others: Timex Sinclair 1000 | TS 1500 | TS 2048 | TS 2068 | SAM Coupé | Didaktik | Hobbit | Sprinter | Pentagon

ca:ZX Spectrum

cs:Sinclair ZX Spectrum da:ZX Spectrum de:Sinclair ZX Spectrum es:ZX Spectrum fr:ZX Spectrum it:Sinclair ZX Spectrum hu:Sinclair Spectrum nl:ZX Spectrum pl:Sinclair ZX Spectrum pt:ZX Spectrum ru:ZX Spectrum sv:ZX Spectrum uk:ZX Spectrum


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