Sinclair’s computers — and successors











THE SPECTRUM is the best and most famous ZX computer — but it’s worth remembering the other computers that Sit Clive Sinclair had a hand in designing before the ZX range was conceived.

By the late Seventies, Sinclair was running out of road. He’d hit trouble selling calculators and digital watches, and had been trying to make and sell a pocket-sized TV set since the Sixties. At last he’d produced one, but it was unreliable and difficult to make.

One plan to raise money for the TV project involved a computer, the NewBrain. Britain’s Labour Government bought a large stake in Sinclair’s firm, Sinclair Radionics, to try to keep things going — but lost confidence after a while. Radionics was split up and Sinclair left to run a new firm, Science Of Cambridge.

“By the late Seventies, Sinclair was running out of road”

The NewBrain was sold to Newbury Labs, then to Grundy; at one time it was going to be the official BBC micro, but it reached the market too late and didn’t catch on.

Over at Science Of Cambridge. Sinclair and an engineer called Chris Curry pooled their experience and invented a horrid wrist calculator, with keys you could press in three different directions for various functions — a sign of things to come!


Then they dreamed up a computer system which has never been beaten on price or uselessness — the MK-14. It used an obscure processor called an SC/MP, mainly because the firm that made it offered to design the computer for nothing as long as Sinclair used its chip.

The MK-14 had a calculator display and keyboard, 0.25K of memory, and no box. Sinclair sold 10,000, and decided that computers were a good way to raise money. Science Of Cambridge changed its name to Sinclair Research. And after moonlighting for a while, Chris Curry left, to set up Acorn computers.

In 1980 the first ZX computer was produced — the ZX-80, designed by Jim Westwood and with software by John Grant. The ZX-80 looked very much like a real computer, though it was made of bendy plastic, had no keys and was less than a quarter of the size it appeared in the glossy adverts.

You could program it in BASIC, using a TV display, and save programs on cassette. But lots of improvements were needed. The ZX-80 contained only 1K of memory, and it could only work with whole numbers between -32788 and 32767 — like the ZIP compiler in the CRASH Tech Tape. Worst of all, the screen went blank when you pressed a key or ran a program!

Still, the ZX-80 was a success, and even spawned a clone — the CompShop Micro Ace. A 16K RAM pack — prone to fall off at inconvenient moments — was produced, and various ingenious tricks were used to stop the machine overheating.


Within a year the ZX-80 had been redesigned, with a custom chip in it to make copying more difficult, and with a much-improved display that allowed programs to run while the screen display was visible — albeit at about a quarter of the ZX-80’s speed. And ZX BASIC was souped up to handle text and floating-point mathematics, though square roots didn’t work properly at first.

The result was the ZX-81: a big improvement, launched in March 1981 at a price that undercut the ZX-80 by £30! The cloned Micro Ace disappeared, but Acorn Computers, founded by Sinclair’s former colleague Chris Curry, got the BBC contract — the ZX-81 had only a black-and-white display.

The ZX-80 had been assembled for Sinclair by part-time home workers, but the ZX-81 was obviously going to sell too many for this arrangement to work. So Sinclair did a deal with Timex, which owned a big factory in Scotland. In return for building the ZX-81 Timex was allowed to sell it in the USA, paying Sinclair a 5% royalty.

The ZX-81 sold well — as did the US version, the TMS-1000, when it popped up in 1982. But Sinclair was still after the BBC contract, and in the summer of 1982 he announced the ZX Spectrum — a colour computer aimed at would-be programmers, with 16K or 48K memory. The extra 32K was fitted on an extra board inside the computer, so it couldn’t fall off.


The Spectrum hardware was designed by Richard Altwasser, now at Amstrad, and the software was adapted from the ZX-81’s by Stephen Vickers. The Spectrum had a new custom chip which could keep a colour display up yet hardly slow the processor at all — but a last-minute bodge was needed to make the keyboard work properly. This was the ‘dead cockroach’ modification: a chip soldered on its back with its legs in the air!

At £125 for 16K, or £175 for 48K, the Spectrum was very cheap and very powerful for its day. The 48K model seemed such a good deal that it sold eight times as well as the 16K model from the start, so a new version was produced — the issue 2 — which could hold 48K on one board. The issue 2 had blue keys, rather than grey ones, to make the lettering all over the keys easier to read under electric light.

Meanwhile Altwasser and Vickers left Sinclair to set up their own firm, Jupiter Cantab, selling a small fast computer that was a cross between a Spectrum and a ZX-80. Their Jupiter Ace flopped.


Sinclair refined the Spectrum again in 1983, making BEEP slightly louder, using a cooler logic array, and adding a minor tweak which unfortunately stopped lots of sloppily-written games recognising the keyboard. This Spectrum was the infamous issue 3.

Back in the USA Timex was bemused by the success of the TMS-1000, and tried to follow it with a 16K variation, the TMS-1500. It flopped, so Timex came out with the TMS-2068 — a superSpectrum with graphics much like the new SAM and sound like a Spectrum 128K. That flopped too, mainly because of competition in the US market and poor software compatibility. Timex gave up in February 1984.

Meanwhile, the rubbery Spectrum keyboard was universally hated, so Sinclair tried to develop something better-looking. The result was the Spectrum +.

Brilliantly, with the + Sinclair preserved total compatibility by using exactly the same circuits as in an old Spectrum, in a new box. And the + sold well, for a while, though the routines to read the keys still insisted you pressed them one at a time — fine for rubber keys, but now very frustrating.


Sinclair had been putting off plans for a superSpectrum since 1982. He spent most of 1983 designing a portable business computer, but at the last moment a near-random collection of design features merged into the Sinclair QL. The QL was launched, designed, manufactured and made to work, in that order.

In 1985 Sinclair’s main distributor, Prism, collapsed. The QL price was slashed in half. Sinclair, now a knight, was busy advertising electric tricycles. Robert Maxwell stepped in, sniffed the air, and stepped out again.

And by now the Spectrum was not considered sophisticated, even with the new keyboard. People began to demand more memory, interfaces and better sound. A mixture of new and TMS-2068 features were cobbled together to make the Spectrum 128K. The money for the 128 came from Spain, so that’s where it was launched.

In January 1986 the Spectrum 128K was launched in the UK, in desperate bid by Sinclair to look busy as debts piled up. But by March the bank had closed Sinclair’s accounts and the company staff were paid on the firm’s behalf by a large retailer that took stock in return.


On April 71986 Amstrad bought the right to make Spectrums, and to kill the QL, for just £5 million, and also paid £11 million for the remaining stocks.

Unconfirmed reports suggest that about 4 million standard Spectrums were produced by Sinclair Research. And there must be about 500,000 128s in circulation now, with the bulk of those being first-edition Amstrad +2s.

A few Sinclair staff moved to Amstrad and produced the +2: a 128 in a new box with a cassette drive ‘glued on’, as Amstrad boss Alan Sugar put it.

A year later came the first true Amstrad Spectrum — the +3, minus Sinclair chips and plus the disk system from Amstrad’s scrapped CPC range. The +3 is a new design, not very compatible with the old Spectrum and its wealth of 48K hardware and software.

And reports from abroad suggest that new +2s will contain stripped-down +3 boards, rather than the relatively costly but compatible +2 design. (To tell the old version from the new one, press BREAK and reset at once to get the TV tuning display. Then press the six keys QAZ and PLM at once. A new, less compatible +2 will go into a self-test mode, as on the +3, whereas an older +2 will ignore the keys.)

Clive Sinclair is now selling a portable computer called the Z88, designed by Jim Westwood and using the same Z80 processor as the ZX range. He’s still trying to raise money to do other things.

Richard Altwasser, who designed the first Spectrum hardware, heads Amstrad’s tiny hardware-design group, which has little time for the Spectrum.

The future now seems to lie with machines like Miles Gordon Technology’s SAM. But whatever happens, the ZX Spectrums will be around for a long time yet.