Editing ZX80 (section)

== Expansion ==
[[File:Sinclair ZX80 with 8K upgrade keyboard at Powerhouse Sydney (filtered retouched).jpg|thumb|Upgraded ZX80 showing the ZX81-style replacement keyboard overlay for use with the 8K ROM]]

Other than the built-in cassette and video ports, the only provided means of expansion was a slot opening at the rear of the case, which exposed an expansion bus [[edge connector]] on the motherboard. The same slot bus was continued on the ZX81, and later the [[ZX Spectrum]], which encouraged a small [[cottage industry]] of expansion devices, including memory packs, [[printer (computing)|printers]] and even [[floppy drive]]s. The original Sinclair ZX80 RAM Pack held either 1, 2 or 3&nbsp;KB of [[Static random-access memory|static RAM]]<ref name='fjkraan'>{{cite web |title=1 to 3K byte memory expansion RAM PACK for the Sinclair ZX80 |url=https://fjkraan.home.xs4all.nl/comp/zx80/rampack.html |archive-url=https://archive.today/20130222225950/http://fjkraan.home.xs4all.nl/comp/zx80/rampack.html |url-status=dead |archive-date=22 February 2013 |website=F J Kraan |access-date=8 December 2019 }}</ref>  and a later model held 16&nbsp;KB of [[Dynamic random-access memory|dynamic RAM]] (DRAM).<ref>{{cite web |title=Ultra Rare Vintage Sinclair ZX80 16K Byte Ram Pack (Mint) |url=https://www.ebay.co.uk/i/293012513981?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=293012513981&targetid=595627780033&device=c&mktype=pla&googleloc=1007408&poi=&campaignid=6619152134&mkgroupid=84510981728&rlsatarget=pla-595627780033&abcId=1140496&merchantid=9752904&gclid=EAIaIQobChMIt_WWg-u05gIVRrTtCh1bRg9fEAQYASABEgJl3vD_BwE |website=Ebay |access-date=14 December 2019}}{{dead link|date=September 2021}}</ref> With software, the computer can use up to 48 KB of memory.<ref name="heuristics198206">{{Cite magazine |last=Ornstein |first=David B. |date=June 1982 |title=More Memory for the ZX80 |url=https://archive.org/details/byte-magazine-1982-06/page/n41/mode/1up?view=theater |access-date=2025-03-16 |department=Letters |magazine=BYTE |pages=40,42}}</ref>

Following the ZX81's release, a ZX81 8&nbsp;KB [[read-only memory|ROM]] was available to upgrade the ZX80 at a cost of around 20% of a real ZX81. It came with a thin keyboard overlay and a ZX81 manual. By simply taking off the top cover of the ZX80 and prying the old ROM from its socket and carefully inserting the new ROM and adding the keyboard overlay, the ZX80 would now function almost identically to the proper ZX81 – except for SLOW mode, due to the differences in hardware between the two models. The process was easily reversed to return the ZX80 to its original configuration.<ref>{{cite magazine |title=Advertisement for ZX Printer |magazine=Your Computer |date=October 1981 |volume=1 |issue=3|pages=42–43 |url=https://archive.org/details/your-computer-magazine-1981-10/page/n41 |access-date=13 December 2019}}</ref>

One common modification by hobbyist users was to attach a full-size keyboard, optionally moving the motherboard into a larger case. This had the dual advantages of making the machine easier to type on, while increasing ventilation to the motherboard.<ref>{{cite magazine |title=DK'Tronics advertisement for full sized keyboard |magazine=Your Computer |date=May 1982 |page=5 |volume=2 |issue=5 |url=https://archive.org/details/your-computer-magazine-1982-05/page/n5 |access-date=13 December 2019}}</ref>