I have six main units, three power adapters and three ZX 16K RAM.
type computer
country UK
year 1982
os basic
cpu Zilog Z80
speed 3.25 MHz
ram 1 KB
rom 8 KB
graphic 24 x 32
colors mono
sound none
ports RF, Z80 bus, tape
The Sinclair ZX81 — The Million-Seller
Released in March 1981 at £49.95 in kit form (£69.95 assembled), the Sinclair ZX81 was a dramatic refinement of the ZX80 that achieved even lower prices through the use of a single custom ULA (Uncommitted Logic Array) chip that replaced many of the ZX80’s discrete components. The ZX81 sold over 1.5 million units, was licensed to Timex Corporation for US and Canadian sales as the Timex Sinclair 1000 (where it sold over 600,000 units), and became the foundation of the British home computing revolution. For a brief period in 1982-83, the ZX81 was the best-selling home computer in the world.
The ULA — Custom Chip Revolution
The ZX81’s custom ULA, designed by Ferranti, consolidated the ZX80’s many chips into a single component — dramatically reducing manufacturing cost and complexity. This approach of using custom chips to achieve impossible price points would become central to British home computing, with both the ZX Spectrum and Amstrad CPC using similar custom chip strategies. The ULA also eliminated the ZX80’s display flicker problem — the ZX81 could display a stable picture while performing calculations, a significant usability improvement over its predecessor.
The 16K RAM Pack
The ZX81’s most famous accessory was the 16K RAM Pack — a module that plugged into the rear expansion port and expanded the base 1 KB of RAM to 17 KB, making far more complex programs possible. The RAM Pack was notoriously prone to causing the ZX81 to crash if slightly disturbed — the ”wobbly RAM pack” problem became legendary among ZX81 users, inspiring a generation of hardware hacks and third-party solutions. Despite this frustration, the RAM Pack transformed the ZX81 from a toy into a genuine programming tool, and many users’ first serious programs were written on a 16K-expanded ZX81.