Editing ZX Spectrum (section)

== Sinclair Research models ==

=== ZX Spectrum 16K/48K ===
[[file:ZXSpectrum48k.jpg|thumb|ZX Spectrum 16K/48K (Dimensions (mm): 233×144×30 (W×H×D) @ ≈552 grams).<ref name = HCHOF>{{cite web | url = http://www.gondolin.org.uk/hchof/hchof.php | title = The Home Computers Hall of Fame, The Machines | last = Stratford | first = Christopher | date = 11 May 2014 | website = gondolin.org.uk | archive-url = https://web.archive.org/web/20150317112736/http://gondolin.org.uk/hchof/hchof.php | archive-date = 17 March 2015 | url-status = live | access-date = 31 March 2015 }}</ref>]]

The original ZX Spectrum is remembered for its rubber [[chiclet keyboard]], diminutive size and distinctive rainbow motif. It was originally released on 23 April 1982 with 16&nbsp;KB of RAM for {{inflation|UK|125|1982|fmt=eq|cursign=£|orig=yes}} or with 48&nbsp;KB for {{inflation|UK|175|1982|fmt=eq|cursign=£|orig=yes}};<ref name="High Street Spectrum">{{Cite journal |date= February 1983 |title= The High Street Spectrum |journal= ZX Computing |page= [https://archive.org/details/ZX-computing-1983-02/page/n42 43] |url= https://archive.org/details/ZX-computing-1983-02 |access-date= 27 April 2016 |url-status= live |archive-url= https://web.archive.org/web/20170316134253/https://archive.org/details/ZX-computing-1983-02 |archive-date= 16 March 2017 }}<!-- This cannot be fixed via Wayback archive due to robots.txt preventing archiving of the site. --></ref> these prices were reduced to {{inflation|UK|99|1983|fmt=eq|cursign=£|orig=yes}} and {{inflation|UK|129|1983|fmt=eq|cursign=£|orig=yes}} respectively in 1983.{{sfn|Gilbert|1983a|p=13}} Owners of the 16&nbsp;KB model could purchase an internal 32&nbsp;KB RAM upgrade, which for early "Issue 1" machines consisted of a [[daughterboard]]. Later issue machines required the fitting of 8 [[dynamic random-access memory|dynamic RAM]] chips and a few [[transistor-transistor logic|TTL]] chips. Users could mail their 16K Spectrums to Sinclair to be upgraded to 48&nbsp;KB versions. Later revisions contained 64&nbsp;KB of memory but were configured such that only 48&nbsp;KB were usable.<ref name = ys-64k-1984-09>{{Cite journal | last = Goodwin | first = Simon | date = September 1984 | title = Suddenly, it's the 64K Spectrum! | journal = [[Your Spectrum]] | issue = 7 | pages = 33–34 | url = http://www.users.globalnet.co.uk/~jg27paw4/yr07/yr07_33.htm | archive-url = https://web.archive.org/web/20140522194918/http://www.users.globalnet.co.uk/~jg27paw4/yr07/yr07_33.htm | archive-date = 22 May 2014 | url-status = live | access-date = 31 March 2015 | quote = 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. }}</ref> External 32&nbsp;KB RAM packs that mounted in the rear expansion slot were available from third parties. Both machines had 16&nbsp;KB of onboard ROM.{{sfn|Leigh|2018|p=68}}

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.<ref name = ps-s48kv-2003-09>{{cite web | url = http://www.nvg.ntnu.no/sinclair/computers/zxspectrum/spec48versions.htm | work = Planet Sinclair | title = Spectrum 48K Versions | last = Owen | first = Chris | archive-url = https://web.archive.org/web/20150321023603/http://rk.nvg.ntnu.no/sinclair/computers/zxspectrum/spec48versions.htm | date = 6 September 2003 | archive-date = 21 March 2015 | url-status = live | access-date = 31 March 2015 | quote = 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... }}</ref> Although the official service manual states that approximately 26,000 of these original boards were manufactured,<ref name="Servicing">{{cite book |last1=Thorn (EMI) Datatech Ltd|title=Servicing Manual For ZX Spectrum |date=March 1984 |publisher=Sinclair Research Ltd |page=4.3 |url=https://k1.spdns.de/Vintage/Sinclair/82/Sinclair%20ZX%20Spectrum/Repair/ZX%20Spectrum%20Service%20Manual%20(OCRed).pdf |access-date=31 January 2019 |archive-url=https://web.archive.org/web/20190201013410/https://k1.spdns.de/Vintage/Sinclair/82/Sinclair%20ZX%20Spectrum/Repair/ZX%20Spectrum%20Service%20Manual%20%28OCRed%29.pdf |archive-date=1 February 2019 |url-status=live }}</ref> 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.<ref>{{Cite web|title=ZX Spectrum Models|url=https://spectrumforeveryone.com/technical/zx-spectrum-models/|access-date=9 September 2021|website=Spectrum for Everyone|language=en-GB|archive-date=9 September 2021|archive-url=https://web.archive.org/web/20210909125915/https://spectrumforeveryone.com/technical/zx-spectrum-models/|url-status=live}}</ref> An online tool now exists to allow users to ascertain the likely issue number of their ZX Spectrum by inputting the serial number.<ref>{{Cite web|title=Spectrum For Everyone Serial DB|url=https://serials.spectrumforeveryone.com/|access-date=9 September 2021|website=Spectrum For Everyone Serial DB|language=en|archive-date=9 September 2021|archive-url=https://web.archive.org/web/20210909125915/https://serials.spectrumforeveryone.com/|url-status=live}}</ref>

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.{{sfn|Popular Computing Weekly|1983b|p=6}} 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.{{sfn|Popular Computing Weekly|1983b|p=6}}{{sfn|Backhurst|1983a|p=5}}

=== ZX Spectrum+ {{anchor|plus}}===
[[file:ZX Spectrum+.jpg|thumb|ZX Spectrum+ (Dimensions (mm): 319×149×38 (W×H×D))<ref name=HCHOF />]]

Development of the ''ZX Spectrum+'' began in June 1984,{{sfn|Denham|1984b|p=104}} and was released on 15 October that year at £179.<ref name="New Spectrum">{{Cite journal |date= December 1984 |title= News: New Spectrum launch |journal= [[Sinclair User]] |issue= 33 |page= 11 |url= http://www.sincuser.f9.co.uk/033/news.htm |access-date= 19 August 2006 |url-status= dead |archive-url= https://web.archive.org/web/20060924094040/http://www.sincuser.f9.co.uk/033/news.htm |archive-date= 24 September 2006 }}</ref><ref name='hcw231084'>{{cite magazine|title=Spectrum surprise!|magazine=Home Computing Weekly|issue=85|publisher=Argus Specialist Publications|date=23 October 1984|page=1|url=https://spectrumcomputing.co.uk/page.php?issue_id=2651&page=1|access-date=23 May 2021|archive-date=24 September 2020|archive-url=https://web.archive.org/web/20200924170531/https://spectrumcomputing.co.uk/page.php?issue_id=2651&page=1|url-status=dead}}</ref><ref name="PSZX+">{{cite web |url=http://www.nvg.ntnu.no/sinclair/computers/zxspectrum/specplus.htm |work=Planet Sinclair |last=Owen |first=Chris |access-date=21 August 2006 |title=ZX Spectrum+ |url-status=live |archive-url=https://web.archive.org/web/20110903053833/http://www.nvg.ntnu.no/sinclair/computers/zxspectrum/specplus.htm |archive-date=3 September 2011 }}</ref> It was assembled by AB Electronics in [[South Wales]] and [[Samsung]] in South Korea.<ref name="Goodwin-145" /> This 48 KB Spectrum introduced a new [[Sinclair QL|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&nbsp;KB model. The machine outsold the rubber-key model two to one,{{sfn|Denham|1984b|p=104}} however, some retailers reported a failure rate of up to 30%, compared with a more typical 5–6% for the older model.<ref name="PSZX+" /> In early 1985, the original Spectrum was officially discontinued, and the ZX Spectrum+ was reduced in price to £129.{{sfn|Bourne|1985a|p=7}}

=== ZX Spectrum 128 {{anchor|spectrum128}}===
[[file:ZX Spectrum128K.jpg|thumb|ZX Spectrum 128]]

In 1985, Sinclair developed the ZX Spectrum 128 (codenamed ''Derby'') in conjunction with their Spanish distributor Investrónica (a subsidiary of [[El Corte Inglés]] department store group).{{sfn|Frey|1985|p=5}}{{sfn|Bourne|1985b|p=5}}{{sfn|Frey|1986|p=11}} Investrónica had helped adapt the ZX Spectrum+ to the Spanish market after their government introduced a special tax on all computers with 64&nbsp;KB RAM or less,<ref>{{in lang|es}} Ministerio de Economía y Hacienda (BOE 211 de 3 September 1985), [http://www.boe.es/buscar/doc.php?id=BOE-A-1985-18847 Real Decreto 1558/1985, de 28 de agosto, por el que se aclara el alcance del mínimo específico introducido en la subpartida 84.53.B.II del Arancel de Aduanas, por el Real Decreto 1215/1985] {{webarchive|url=https://web.archive.org/web/20130430111506/http://www.boe.es/buscar/doc.php?id=BOE-A-1985-18847 |date=30 April 2013 }}. Rango: Real Decreto, Páginas: 27743 – 27744, Referencia: 1985/18847.</ref> and a law which obliged all computers sold in Spain to support the Spanish alphabet and show messages in Spanish.<ref name="BOE">{{in lang|es}} Ministerio de Industria y Energía (BOE 179 de 27 July 1985), [http://www.boe.es/buscar/doc.php?id=BOE-A-1985-15611 Real Decreto 1250/1985, de 19 de junio, por el que se establece la sujeción a especificaciones técnicas de los terminales de pantalla con teclado, periféricos para entrada y representación de información en equipo de proceso de datos] {{webarchive|url=https://web.archive.org/web/20130430104621/http://www.boe.es/buscar/doc.php?id=BOE-A-1985-15611 |date=30 April 2013 }}. Rango: Real Decreto, <!--pages, or pp. here? --> Páginas: 23840–23841, Referencia: 1985/15611.</ref>

The appearance of the ZX Spectrum 128 is similar to the ZX Spectrum+, with the addition of a large external [[heat sink|heatsink]] for the internal 7805 [[voltage regulator]] to the right-hand end of the case, replacing the internal heatsink in previous versions. This external [[Heat sink|heatsink]] led to the system's nickname, "The [[Toast rack|Toast Rack]]".<ref>{{cite web|url=http://retrorevivalshop.co.uk/index.php?main_page=product_info&cPath=7&products_id=60|title=Murata 5v Switching Regulator (for Toastrack models)|website=Retro Revival Shop|access-date=13 November 2021|archive-date=13 November 2021|archive-url=https://web.archive.org/web/20211113115246/http://retrorevivalshop.co.uk/index.php?main_page=product_info&cPath=7&products_id=60|url-status=live}}</ref> New features included 128&nbsp;KB RAM with RAM disc commands, three-channel audio via the [[General Instrument AY-3-8910|AY-3-8912]] chip, [[MIDI]] compatibility, an [[RS-232]] serial port, an [[RGB]] monitor port, 32&nbsp;KB of ROM including an improved BASIC editor, and an external keypad.{{sfn|Wilkins|2015a|p=17}}

The machine was simultaneously unveiled for the first time and launched in September 1985 at the [[SIMO TCI|SIMO '85]] trade show in Spain, with a price of 44,250 [[Spanish peseta|pesetas]]. Sinclair later presented the ZX Spectrum 128 at [[The 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.<ref name="sincuser-49">{{Cite journal|date=April 1985 |title=<!-- wrong title this is quote: -->Clive discovers games – at last |journal=[[Sinclair User]] |issue=49 |page=53 |url=http://www.sincuser.f9.co.uk/049/128lnch.htm |url-status=dead |archive-url=https://web.archive.org/web/20060924093908/http://www.sincuser.f9.co.uk/049/128lnch.htm |archive-date=24 September 2006 }}</ref><ref name=nerd/>

The [[Zilog Z80]] processor used in the Spectrum has a [[16-bit computing|16-bit]] address bus, which means only 64&nbsp;KB of memory can be directly addressed. To facilitate the extra 80&nbsp;KB of RAM the designers used [[bank switching]] so the new memory would be available as eight pages of 16&nbsp;KB at the top of the address space. The same technique was used to page between the new 16&nbsp;KB editor ROM and the original 16&nbsp;KB BASIC ROM at the bottom of the address space.<ref name="128+3-Manual-8">{{cite web|url=http://www.worldofspectrum.org/ZXSpectrum128+3Manual/chapter8pt24.html|title=Spectrum 128+3 Manual, Chapter 8 Part 24|publisher=Amstrad|access-date=20 August 2012|url-status=live|archive-url=https://web.archive.org/web/20120615075843/http://www.worldofspectrum.org/ZXSpectrum128+3Manual/chapter8pt24.html|archive-date=15 June 2012}}</ref>

The new sound chip and [[MIDI]] out abilities were exposed to the BASIC programming language with the command <code>PLAY</code> and a new command <code>SPECTRUM</code> 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&nbsp;KB of RAM. The new commands took the place of two existing user-defined-character spaces causing compatibility problems with certain BASIC programs.<ref name="128+3-Manual-7">{{cite web|url=http://www.worldofspectrum.org/ZXSpectrum128+3Manual/chapter7.html|title=Spectrum 128+3 Manual, Chapter 7|publisher=Amstrad|access-date=20 August 2012|url-status=live|archive-url=https://web.archive.org/web/20120615074428/http://www.worldofspectrum.org/ZXSpectrum128+3Manual/chapter7.html|archive-date=15 June 2012}}</ref> Unlike its predecessors, it has no internal speaker, and can only produce sound from a television speaker.<ref name="128-Manual-9">{{cite web|url=http://www.worldofspectrum.org/ZXSpectrum128Manual/sp128p09.html|title=World of Spectrum – Documentation – ZX Spectrum 128 Manual Page 9|access-date=28 April 2016|url-status=live|archive-url=https://web.archive.org/web/20160424174241/http://www.worldofspectrum.org/ZXSpectrum128Manual/sp128p09.html|archive-date=24 April 2016}}</ref>