1
DEVELOPMENT
Before the ZX80, Sinclair Research was already well
established in the electronics world, pioneering devices such
as cheap calculators and pocket televisions. It had developed a
rudimentary computing kit under the former name of Science
of Cambridge— 197 7’s MK14. But from 198 0, the Sinclair name
would forever be linked with affordable home microcomputers.
>> In the late 197 0s, computers were far too expensive for most
households. Obsessed with making sophisticated electronics
available to all, Clive Sinclair envisaged a new microcomputer
that, with clever simplification and cost-cutting, was affordable.
>> Chief design was entrusted to Jim Westwood, briefed with
something that would cost under £ 100 while still making a profit.
>> Cost-cutting was applied. The base model came with 1 KB
of RAM and no sound output. Video output was black and white
and the membrane keyboard was the worst in all Christendom.
>> It doesn’t have a dedicated video chip but uses an ingenious
workaround. By using static RAM instead of dynamic RAM,
Westwood was able to exploit the Z 80 processor’s unused
dynamic RAM interface to make the CPU do video processing.
>> The downside was that the ZX80 couldn’t process video
output and keyboard input simultaneously, resulting in an
annoying screen flicker with each keypress.
>> Despite its flaws, the ZX80 was a huge success, retailing for
£100 ($138) or £ 80 ($110) in kit form. However, customers soon
discovered they couldn’t do much with 1KB of RAM, making the
16K RAM expansion pack a must-have accessory.
>> The following year, Sinclair upgraded the ZX80 design
with the ZX81, addressing many flaws. The screen flicker was
resolved by introducing “SLOW” mode, which used the Z80’s
interrupt mechanism to control when to output the TV signal.
The ROM was upgraded to include floating-point computations,
additional commands, and ZX Printer support.
>> The ZX81 used an Uncommitted Logic Array (ULA) chip from
Ferranti, reducing the chip count from 21 in the ZX80 to just four.
This allowed Sinclair to sell the ZX81 even cheaper. In March
198 1, the ZX 81 cost £7 0 ($96) assembled, or £50 ($69) for a kit.
2
GAMING
ZX80 games aren’t common, but as the ZX81 doesn’t have
proper graphics, its games were based on text block
characters. They were often ambitious within these limitations.
>> The Gauntlet ( 198 2) is a great arcade bomber, and Mazogs
(1982) is an intriguing maze explorer with cool aesthetics. 3D
Monster Maze ( 198 1) and 3D Defender ( 198 1) push the limits of
ASCII art with first-person 3D perspectives. Brazilian platformer
Em Busca Dos Tesouros ( 198 6) sports impressive animations
and brutally difficult gameplay.
FOR FANS OF BRITISH MICROCOMPUTERS, the Sinclair ZX80 and its successor, the ZX81, were
integral to establishing the home computing scene. The brainchild of British inventor, Sir Clive
Sinclair, the ZX80 first brought affordable home computers to the masses in 198 0.
As we began our research for this column, we heard the news that Sir Clive had passed away,
aged 81. So it seems an even more appropriate time to pay tribute to a computing legend by
covering the machines that kick-started Britain’s coding revolution. – JOHN KNIGHT
YOU’LL NEED THIS
A COPY OF ZESARUX
available from GitHub.
https://github.com/chernandezba/
zesarux/releases
>> Both machines had dedicated masochists who
squeezed whole games into 1KB for stock machines. 1K
Space Intruders (ZX80, 19 81), 1K ZX Chess (ZX81, 19 82),
and Nohzdyve (ZX81, 201 9) are all examples of coding at
its absolute leanest.
>> Clever coders eventually figured out ways of piecing
together one-line slices of Sinclair’s character set to
emulate the look and feel of sprite graphics. Games
like Forty Niner ( 198 2) and Rocket Man ( 198 4) achieved
impressive results, though the geometry looked wonky.
3
LEGACY
While the ZX8 0 had a strong showing with sales
of over 100 ,000, they were dwarfed by the ZX81,
which enjoyed sales of more than 1. 5 million.
>> An enormous fan base developed and conventions
were flooded with Sinclair users. Third-party vendors
sold hardware add-ons, such as disk drives, improved
cases, and better keyboards. Software houses sold
cheap software on cassette, along with endless
programming manuals.
>> Both computers spawned clone machines. The
ZX80 had clones in Brazil and the US, while the ZX81 had
clones in Brazil, Argentina, Hong Kong, and China.
>> In the US, third-party production was licensed to
the Timex Corporation. Its first launch was the Timex
Sinclair 100 0, an NTSC-modified version of the ZX81 that
shipped with 2 KB of RAM.
>> Initial sales were strong but diminished after
customers discovered the limitations of so little RAM.
>> Sinclair’s machines are treasure troves for ASCII art
fans. Paul Farrow’s ZX 80 Kong (2010) nicely re-imagines
the classic Donkey Kong game via text characters.
60 MAXIMUMPC HOL 2021
R&D
