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Founded by Clive Sinclair, Sinclair Research produced the Sinclair ZX80 and the ZX Spectrum, which was the best selling computer in the United Kingdom, competing well against Amstrad and Commodore.

Originally, Sinclair's company was known as Westminster Mail Order, then Science of Cambridge, and Sinclair Computers, before becoming Sinclair Research in 1981.

Sinclair entered the computer market in 1980 with the Sinclair ZX80, which was released in January of that year. One of the first computers available in the UK, it sold for less than a hundred pounds and could be purchased as a kit or as a fully assembled computer. The ZX80 came with 1 KB of static RAM and 4 KB of ROM. There was no sound output. Designed around TTL chips, the only proprietary technology in the ZX80 was its firmware.

The ZX81 used a custom chip that combined the functions of the earlier hardware onto a single chip, reducing the number of chips from twenty-one to four. The hardware functions and system programs were very much the same. The ROM was enhanced and made available as an upgrade for the ZX80 as well. It contained the Sinclair BASIC programming language, an editor, and the operating system. BASIC commands were not entered by typing them out but were selected as in a programmable graphing calculator, in which each key had a few different functions that were selected by context and modes, as well as with the shift key.

The ZX80 and ZX81 were mounted in a small white plastic case with a one-piece blue membrane keyboard on the front. There was no fan and no ventilation slots, so the devices had problems with overheating.

The ZX81 was marketed in North America as the Timex Sinclair. Timex of Portugal also sold the Timex Sinclair models in Portugal and Poland. Timex Sinclair released four computers under the Timex Sinclair label: the TS1000, TS1500, TS2068, and TC2048. A TC3256 computer was proposed but never released.

Released in the UK in 1982, the ZX Spectrum was an 8-bit PC that was originally designed to be the ZX82. Produced from 1982 to 1992, the Spectrum line included eight different models, ranging from the 16 KB RAM entry-level model to the Spectrum +3, with 128 KB RAM. Together, more than five million ZX Spectrums were sold worldwide.

The Spectrum was one of the first mainstream home computers sold in the United Kingdom, with a reception similar to that of the Commodore in the United States. Its rivals in the UK were the Amstrad CPC, BBS Micro, Commodore 64, Dragon 32, Oric-1, and Oric Atmos.

The original Spectrum shipped with a rubber keyboard. Those who bought the 16 KB model could purchase an internal 32 KB upgrade, which consisted of a daughterboard. Later models required the fitting of eight dynamic RAM chips and a few TTL chips, but users could mail their 16 KB machines to Sinclair to be upgraded to 48 KB versions.

The Spectrum+ was released in late 1984. This 48 KB model came in a QL-style case with an injection-molded keyboard and a reset switch. Otherwise, the + model would fit into an original Spectrum case. A do-it-yourself conversion kit was offered to upgrade the earlier Spectrums to the Spectrum+.

Also released in 1984, the Sinclair QL was an upper-end counterpart to the Spectrum, aimed at professional and business markets. It was not commercially successful and was discontinued in 1986.

The ZX Spectrum 128 was similar to the +, but with a large external heatsink that replaced the internal heatsink in previous versions. Otherwise, the RAM was increased to 128 KB, an RS-232 serial port, an RGB monitor port, 32 KB ROM, a BASIC editor, and an external keypad. It was released in 1985.

In May of 1985, Sinclair sold its computer line to Amstrad. The sale did not include the company itself, just the products and the brand.

In 1987, Amstrad released the ZX Spectrum +2A and the +3. They were similar, except that the +3 came with an external disk drive. If an external drive were later added to the +2A, the OS menu would change its identification to a +3. The +3 also added two more 16 KB ROMs, one hosting the reorganized 128 ROM, while the other carried its operating system. This was a modified version of Amstrad's PCWDOS. The ZX Spectrum +2B and +3B were similar in design to the +2A and the +3, with changes to the audio output signal.

The focus of this category is on any of the Sinclair computers, including those made after its product line was sold to Amstrad. Sites whose chief topics are the Sinclair line of computers or subsections of sites featuring substantial information on the topic are appropriate here.



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