Sinclair ZX Spectrum celebrates 30 years

April 23, 2012 | 10:15

Tags: #acorn #amstrad #home-computing #spectrum #zx-spectrum

Companies: #sinclair-research

Today marks the 30th anniversary of the ZX Spectrum, one of the most iconic home computers of the 1980s and the device which propelled Clive Sinclair's company from near-insolvency to a billion-pound giant.

While home computers predated the 80s, it took the combined - and competitive - efforts of Sinclair Research, formerly Science of Cambridge, and Acorn Computers to bring the technology to a level where it was affordable for general-purpose use. Put simply: without the Spectrum and its predecessors, it's highly unlikely that home computing would be as ubiquitous as it is today.

Designed as a response to Acorn's Atom microcomputer, itself an attack on the popularity of Sinclair's simple but low-cost ZX81, the ZX Spectrum was a powerful machine for its era: a Zilog Z80 processor running at 3.5MHz and up to 48KB of RAM in the initial production models - later expanded to 128KB - offered computing enthusiasts impressive performance at a very affordable cost.

Designed by Richard Altwasser, with the casing and its iconic 'dead-flesh' rubber keyboard designed by Rick Dickinson, the Spectrum was a marvel of low-cost computing: unlike its predecessor the ZX81, the Spectrum offered graphics in seven colours at two brightnesses for a total 15 colour palette. To conserve memory, Altwasser had the colour stored separately from the main bitmap in a 32x24 grid of character cells - a novel approach which would win him a patent for his efforts, although one which resulted in the tell-tale 'colour clash' when sprites overlapped.

As with the majority of home computers from the era, the Spectrum loaded directly into a programming language. Written by Nine Tiles' Steve Vickers, Sinclair BASIC provided a powerful programming language with in-built keywords for accessing the graphics modes and sound modulator while providing backwards compatibility for programs written for the older ZX81.

At its release in 1982, the Spectrum cost £125 with 16KB of RAM or £175 with 48KB. While this was a significant bump over the ZX81's headline-grabbing £99 retail price, home computing fans found the Spectrum a worthy upgrade and sales were brisk. Even when rival Acorn won a contract to produce the hardware for the BBC's home computing initiative - the BBC Micro - Sinclair continued to sell thousands of Spectrums, with demand of 200,000 units a month causing supply problems for the company.

The Spectrum would give birth to a range of successor systems, including the ZX Spectrum+ with revised keyboard and the ZX Spectrum 128 with 128KB of memory. Following Sinclair Research's acquisition by rival Amstrad in 1986, the Spectrum would continue to form the heart of the company's home computing offering with the Spectrum +2 adding an in-built tape recorder, and the Spectrum +3 offering a 3in CPC-style disk drive.

The Spectrum would eventually be discontinued in 1992, following several successive hardware projects - including the ill-fated Sinclair Quantum Leap, aimed at the business market - marking the end of the British home computing revolution.

Many in the computing industry today - and, in particular, the games industry - owe their careers to being bought a ZX Spectrum at an early age. Despite this, Sir Clive Sinclair himself is often reticent to discuss the machine - seeing the popularity of the system for gaming, rather than serious computing, as an insult to his creation.

For a great background on the creation of the system, the BBC is running an interview with its designers to mark its 30th anniversary.
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