1981 · Sinclair Research · UK · computer
Sinclair ZX81
Sir Clive Sinclair’s mission to make computing affordable to everyone.
Skip it Trivial to run Needs a keyboard ▶ Watch on YouTube ↗
Sir Clive Sinclair’s mission to make computing affordable to everyone. By utilizing only 4 microchips and a membrane keyboard, the ZX81 broke the $100 price barrier and taught an entire generation of British and American coders BASIC.
With just 1,024 bytes of memory, David Horne coded a playable game of Chess ("1K ZX81 Chess") including an AI engine—one of the most staggering coding feats in history.
Under the hood
- CPU
- Zilog Z80A @ 3.25 MHz with only 1 KB RAM (expandable with 16 KB wobble rampack)
- Sound chip
- None (Completely silent hardware)
- Graphics
- 64 × 48 character block monochrome graphics (No high-res)
- Media
- Cassette Tape & 40-key membrane keyboard
What it cost
about 12% of a month’s pay in 1981 · about $488 today
| UK launch price (£69.95 assembled, £49.95 kit) |
£69.95 (1981)
Brought personal computing under £100 in the UK and $99 in the US via Timex Sinclair. |
|---|---|
| Typical street price | — No verified mass-market street price recorded yet. |
| Units sold | ≈1,500,000 estimate 1.5 million units sold worldwide. |
Why it mattered
With just 1,024 bytes of memory, David Horne coded a playable game of Chess ("1K ZX81 Chess") including an AI engine—one of the most staggering coding feats in history.
Emulating it today
| Emulators | EightyOne, EightyOne (libretro), Fuse |
|---|---|
| Setup effort | Trivial to run (1 on this site's scale) |
| Controls | The original software assumes a keyboard. A desktop setup feels natural; on a handheld, map common keys and keep an on-screen keyboard available. |
| Runs on a handheld | Yes |
Monochrome display and membrane keyboard require snapshot loading (.p files) via EightyOne emulator or RetroArch. The emulator names above are starting points, not a promise that every title or accessory behaves identically. Computer platforms usually add model selection, disk handling and keyboard setup even when CPU emulation itself is mature.
Firmware
This system needs no firmware file. Install an emulator, open a game, and it runs.
How many files you need: none to go and find. No separate firmware file is needed for an ordinary setup.
Firmware details checked 2026-08. Emulator requirements change — see Libretro documentation for the current list.
Where the software is
TOSEC catalogues computer disks and tapes broadly, including many revisions. It is useful for preservation, while a smaller curated selection is usually easier to play.
Copyright: Commercial software remains copyrighted unless its owner explicitly released or relicensed it. Homebrew, public-domain programs and current reissues should be treated separately from abandoned commercial titles.
This site names preservation projects and explains what they are. It does not link to ROM downloads.
Where to start
- 1K ZX81 Chess Chess AI
A full chess game with AI squeezed into under 1,024 bytes.
- 3D Monster Maze First-Person Survival Horror
The world’s first 3D first-person survival game (escape the Tyrannosaurus Rex in a maze!).
- Flight Simulation Flight Sim
Psion’s landmark 16K flight simulator.
- Asteroids Space Shooter
Blocky ASCII rendition of the vector arcade classic.
The verdict
Ultra-austere 1 KB RAM black-and-white computer with a touch membrane keyboard. Mostly of interest to computer history purists studying extreme software optimization (like 1K Chess).
The strongest software can be rewarding, but original controls and setup assumptions may matter more than screenshots suggest.
- Worth it if
- Players curious about sinclair and amstrad and willing to learn how the original machine worked.
- Not for
- Anyone who wants a large, instantly accessible library and no model, firmware or control decisions.
Scored 1/5 for fun today and 2/5 for historical importance. Those two scores decide the label at the top — a machine can matter enormously and still be no fun.
Read more & watch
This page is 50% complete against the facts we try to record for every system. Gaps are shown as gaps.