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SINCLAIR ZX81
Aiming to reduce the complexity and cost of production of the ZX80, Jim Westwood and his peers had the brilliant idea of combining numerous circuits that were part of the Zx80 into a single circuit called ULA (Uncommitted Logic Array), which was developed by the Ferranti company. The ZX81 first hit the market with only 4 integrated circuits and is considered by Sir Clive Sinclair to be a masterpiece and one of his most iconic computers, even though it still had a black and white screen.
Its ROM was manufactured by the Nine Tiles company (as had been the one for the ZX80), namely by John Grant and Steve Vickers. It was the first of its’ kind to be able to handle trigonometric and floating-point operations. This was also the first time the BASIC code validation was made at the same time it was being written, a revolutionary thing at the time.
It had a huge commercial success, having sold over 1.5 million units after its release in 1981. It could be bought both in a kit or already assembled. It was manufactured by TIMEX at the Dundee branch (Scotland). There are version with slight changes that were sold in the USA and France (for instance), as well the Timex Sinclair 1000 clone.
Curiosities:
Some of the ULA versions have a “square-root” bug which made the number for the square root of 0.25 to be incorrect. At a later time correction to this problem were developed, turning all the many boards into collectors items.