Clive Sinclair And The Small Home Computer Revolution
Written by Harry Fairhead   
Tuesday, 22 July 2014
Article Index
Clive Sinclair And The Small Home Computer Revolution
From calculator to computer
ZX80 and beyond


The first Sinclair product that we can classify as to do with computing was a calculator.

But what a calculator!

At a time (1972) when electronic calculators were desk bound the Sinclair Executive was a marvel of miniaturisation. It was the first pocket calculator and it wasn't very expensive. It won design council awards and was put on show at the Museum of Modern Art in New York. But it wasn't much of an innovation electronically. It used a standard chip with a, typical Sinclair, power saving trick of pulsing the power supply.




After the Executive came a range of lower priced pocket calculators.

These had a reputation for not being very reliable - although much of the trouble was due to a poor design for the on/off switch which was basically a spring contact on the printed circuit board. Then a scientific calculator was produced by reprogramming a standard off the shelf chip again another typically Sinclair trick.

Finally work did begin on a personal computer design - but the bottom fell out of the calculator market and the National Enterprise Board (NEB) took over Sinclair Radionics. The design was sold to Newbury - a maker of VDUs - and it turned up some time later as the NewBrain. A good and reliable machine but it lacked the flair of a true Sinclair product and used lots of discrete chips..

Financially things got worse at Sinclair Radionics. None of the products that had been launched to replace the lost calculator market were proving a success.

The incredibly innovative Black Watch - the first Quartz watch - was having so many reliability problems that most were returned for repair as soon as they were shipped. The miniature TV wasn't selling well and also had reliability problems. In the end, enough was enough and the NEB split Sinclair Radionics up.




While all this was going on Chris Curry had been looking after a small venture called Science of Cambridge. This company was to be Sinclair's lifeboat and indeed it turned into Sinclair Research soon after the loss of Sinclair Radionics.

Science of Cambridge operated in much the same way as the early Sinclair company. They produced kits and the advertising that they took was unmistakably "Sinclair" even though the magic name appeared nowhere. After a wrist calculator and a few other things the real breakthrough was the MK14.



The MK14


This was a microprocessor trainer - a membrane keyboard, LED display and that's about all. The MK14 was designed by Ian Williamson but it sort of counts as Sinclair's first computer. It certainly made him think hard about producing something a little better. It also inspired Chris Curry who, fired by a vision of better machines, set up Acorn with Herman Hauser. Their first product was the Acorn System 75 - a direct competitor to the MK14.

These computer trainers were very primitive. All you could do was to enter some machine code in hex - if you look at the keyboard you will see the abcde keys on the right. When you ran the program the result was shown in hex on the small display. It might not seem much by today's standards but at the time - it was a computer and one you could own. The possibilities were limitless - as long as the output was in hex. 


In 1980 the ZX80 was launched - the smallest and cheapest home computer yet. It used a Z80 microprocessor, had 1K of RAM and a 4KByte ROM which contained a specially written integer Basic - the whole lot cost £99.95, or £79 in kit form.


The ZX80


The innovations that made this possible were typically Sinclair. For example, was no video controller chip - the Z80 generated the video signal. This saved a very expensive component but meant that the machine couldn't compute and display at the same time - so when it was working the screen flashed and sometimes rolled until the video signal came back.

The ZX80 incorporated far too many innovations for me to mention them all but the keyboard is especially noteworthy. This was a membrane design, typical of the Sinclair calculator range but it had the Basic keywords included on it. This allowed the user to enter PRINT by pressing a single key and simplified the design of the Basic interpreter because there was no need to parse the input. Simple and effective.

Perhaps one of the biggest factors in the sucess of the ZX80 was the advertising. It made it look like something worth buying. Most early adopters weren't disapointed when they first got it but the only fun you could have with it was writing programs. The video hardware made it very difficult to create any sort of game because the display was switched off when the machine was doing any sort of computation. The ZX80 was more like a calculator that you could program in basic and used a TV to display its output.











Last Updated ( Tuesday, 12 August 2014 )