ZX81
| |
| Developer | Sinclair Research |
|---|---|
| Type | Computers |
| Release date | 1981 |
| Discontinued | 1984 |
| Predecessor | ZX80 |
| Successor | ZX Spectrum |
| Emulated | ✓ |
The ZX81 was a Z80-based home computer produced by Sinclair Research and manufactured in Scotland by Timex Corporation released on March 5, 1981, and had a retail price of $99.95 ($354 in 2026). It had a Z80 at 3.25 MHz with 1KB of RAM.
It was the successor to Sinclair's ZX80 and the predecessor of the ZX Spectrum and was hugely successful, and more than 1.5 million units were sold before it was discontinued. The ZX81 was designed to be small, simple, and above all cheap, using as few components as possible to keep the cost down.
Video output was to a television set rather than a dedicated monitor. Programs and data were loaded and saved onto audio tape cassettes. It had only four logic chips on board and a mere 1 KB of memory. The machine had no power switch or any moving parts and used a pressure-sensitive membrane keyboard for manual input.
Its distinctive design brought its designer, Rick Dickinson, a Design Council award. The ZX81 could be bought by mail order in kit form or pre-assembled. It was the first cheap mass-market home computer that could be bought from high street stores, led by W.H. Smith and soon many other retailers.
The ZX81 marked the first time that computing in Britain became an activity for the general public, rather than the preserve of businesspeople and electronics hobbyists. The ZX81's commercial success made Sinclair Research one of Britain's leading computer manufacturers and earned a fortune and an eventual knighthood for the company's founder, Sir Clive Sinclair.
Emulators
[edit | edit source]| Name | Platform(s) | Latest version | libretro | Relative Speed[N 1] | License | Active | Recommended |
|---|---|---|---|---|---|---|---|
| PC / x86 | |||||||
| CLK |   
|
2026-07-23 | ✗ | 100.0% | MIT (Permissive) | ✓ | ✓ |
| ZEsarUX |    
|
13.0 | ✗ | 110.9% | GPL (Copyleft) | ✓ | ✓ |
| EightyOne (81) |
|
1.41 | ✓ | 100.0% | GPLv2 (Copyleft) | ✓ | ✓ |
| Spud81 |
|
0.221 | ✗ | 114.9% | Proprietary | ✗ | ~ |
| SZ81 (xz80 & z81 based) |
|
2.1.7 2.3.10 (Unofficial) |
✗ | 100.0% | GPLv2 (Copyleft) | ✗ | ~ |
| MAME |
|
0.289 | ✓ | Not tested | GPLv2 BSD-3-Clause |
✓ | ✗ |
| MTMW (aka 'MulTiMachine') |
|
1.30b | ✗ | Not tested | Proprietary | ✗ | ✗ |
| Pantheon |
|
16.458 | ? | ? | Proprietary | ✓ | ? |
| No$ZX | 
|
2.0 | ✗ | 100.1% [N 2] |
Proprietary | ✗ | ✗ |
| VB81 XuR |
|
28/08/2025 | ✗ | 100.5% | GPLv2 (Copyleft) | ✓ | ✗ |
| VB81 |
|
1.30 | ✗ | Not tested | GPLv2 (Copyleft) | ✗ | ✗ |
| XTender2 |
|
beta 13 | ✗ | Not tested | Proprietary | ✗ | ✗ |
| ZX81 Emulator (Paul Robson) |
|
4.00 | ✗ | 101.5% | Proprietary | ✗ | ✗ |
| Mobile / ARM | |||||||
| SZ81 (xz80 & z81 based) |
  
|
2.1.7 | ✗ | 100.0% | GPLv2 (Copyleft) | ✗ | ✗ |
| ZEsarUX |  
|
13.0 | ✗ | 110.9% | GPL (Copyleft) | ✓ | ✓ |
| ZX81 iOS | 
|
2.0.4 | ✗ | 100.0% | ? | ✓ | ~ |
| Consoles | |||||||
| DS81 | 
|
1.3 | ✗ | Not tested | GPLv2 (Copyleft) | ✗ | ✓ |
- ↑ As calculated by Carlo Delhez's clkfreq, originally distributed with his XTender emulator. The ZX81 has relatively complicated timing mechanics, depending on signalling of WAIT during NMI; relative speed is a measurement of how closely an emulator matches a real machine in terms of clock cycles spent processing within a frame. 100.0% denotes the same execution speed as a real machine.
- ↑ After turning off the simulated hardware improvements that were not standard in the original computer.
Notes
[edit | edit source]- www.retroisle.com (Page showing five old emulators for ZX81, and sometimes the Spectrum and other machines)
- www.worldofspectrum.org's list (Short list of old Science of Cambridge MK-14, ZX80, ZX81 / TS1000, Sinclair QL and Jupiter ACE emulators)
- zx81.eu5.org (Brazilian ZX81 fan-site - emulators list page is in English. Shows list of old ZX81 emulators & links to other resources.)
- floppydays.libsyn.com (Podcast episode describing the emulators available for the ZX80 / ZX81 which also uses the Carlo Delhez's clkfreq rating. Also has huge lists of resources for all things ZX80/81 related.)
- [1] (Schematic) There was also an ASTEC RF modulator and a voltage regulator.
![[1]](http://www.robotsandcomputers.com/computers/manuals/zx81_sch.jpg){kind=link}