Timex Sinclair was a joint venture established in December 1982 between the British company Sinclair Research and Timex Corporation in an effort to gain an entry into the rapidly growing early-1980s home computer market in North America.
99-455: The choice of partnership was natural, as Timex was already the main contractor for manufacture of Sinclair's ZX81 and ZX Spectrum computers at its Scottish plant in Dundee . Due to large demand another manufacturer was needed, so Timex Portugal ( TMX Portugal Lda , a Portuguese Timex subsidiary), with skilled and relatively cheap labor force, took on the production of models to be exported to
198-486: A Design Council award. The ZX81 could be bought by mail order preassembled or, for a lower price, in kit form. It was the first inexpensive mass-market home computer to be sold by high street stores, led by W. H. Smith and soon many other retailers. The ZX81 marked the point when computing in Britain became an activity for the general public rather than the preserve of businessmen and electronics hobbyists. It produced
297-445: A '1' bit is nine pulses, so the baud rate varies between 400 bit/s for all "0"s and 250 bit/s for all "1"s. A file with equal amounts of '0's and "1"s would be stored at 307 bit/s (38 B/s). This provides a somewhat temperamental storage medium for the machine, which has no built-in storage capabilities. The ZX81 requires 420 mA of current at 7–11 V DC , delivered via a custom 9 V Sinclair DC power supply. The ULA chip, described by
396-400: A 1982 interview with Your Computer , There are two big markets. There is the hobbyist and the man in the street. The hobbyist was a dead certainty. We knew we could sell to him because we have so much experience of it and we were offering a better product. The much less certain prospect was the man in the street. There the view was that if we offered him a computer plus a self-training book at
495-691: A BBC-branded home computer to tie in with the series. When Clive Sinclair heard of the project in December 1980, he wrote to the BBC informing them that he would be announcing a new version of the ZX80, to be called the ZX81, in early 1981. It would remedy some of the ZX80's deficiencies and would be both cheaper and more advanced. Sinclair wanted the ZX81 to be a candidate for the BBC contract and lobbied for its adoption. He pointed out that there were already 40,000 users of
594-561: A company called Ablesdeal Ltd, which he had established in 1973 and later renamed Science of Cambridge. It became a vehicle through which he could pursue his own projects, free of the interference of the NEB. Despite his later success in the field, Sinclair saw computers as merely a means to an end. As he told the Sunday Times in April 1985, "We only got involved in computers in order to fund
693-415: A high speed compared to mass storage which is slower but less expensive per bit and higher in capacity. Besides storing opened programs and data being actively processed, computer memory serves as a mass storage cache and write buffer to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as it is not needed by running software. If needed, contents of
792-586: A huge community of enthusiasts, some of whom founded their own businesses producing software and hardware for the ZX81. Many went on to have roles in the British computer industry. The ZX81's commercial success made Sinclair Research one of Britain's leading computer manufacturers and earned a fortune and an eventual knighthood for the company's founder, Sir Clive Sinclair . The ZX81 has a base configuration of 1 KB of on-board memory that can officially be expanded externally to 16 KB. Its single circuit board
891-402: A keen enough price he would buy by mail order – which, of course, he has. According to Ben Rosen , by pricing the ZX81 so low, "Sinclair has opened up a completely new market among people who had never previously considered owning a computer." Clive Sinclair acknowledged the role that guesswork had played in his decision to launch the ZX81 on such a large scale: "It was a surmise that the man in
990-425: A lower rate of failure on our computers than anybody else in the world, and the reason for that is that we do everything to keep the quality right. The ZX81 production line is a miracle of efficiency; after all, one is made every 10 seconds. They go through the most amazing quality control. Also we have a far lower component count than anyone else. We have only four chips where everyone else has 40. Sinclair attributed
1089-474: A new market in 1972 when it launched the first "slimline" pocket calculator, the Sinclair Executive . Radionics followed up by launching a wide range of pocket calculators. The company's subsequent expansion made it Europe's biggest calculator manufacturer by 1975. By the late 1970s, however, Sinclair Radionics was experiencing serious difficulties . It lost its ability to compete effectively in
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#17327937509241188-428: A plastic overlay, connected in a matrix of 8 rows and 5 columns. The ZX81 uses a standard QWERTY keyboard layout displaying 20 graphic and 54 inverse video characters. However ZX81 BASIC commands are not typed in letter by letter, instead each key has up to five key functions. This is how the user displays the ZX81's BASIC keywords, functions, mathematical operations and graphics. The ZX81 key's function
1287-413: A question of what the machine ought to be able to do, but more what could be crammed into the machine given the component budget he'd set his mind on. The only firm brief for the '81 was that the '80s math package must be improved. The new ROM incorporated trigonometric and floating-point functions, which its predecessor had lacked – the ZX80 could only deal with whole numbers. Grant came up with one of
1386-405: A reasonable job and sensibly provides lots for the reader to do. It's quite honest about the [ZX81]'s shortcomings and provides hints and tips for ways round them ... Best of all, the manual is complete and comprehensive. There's some fairly advanced and often undisclosed information in there. The beginner won't understand it for a long time but if he or she learns some more advanced ideas, the manual
1485-437: A reputation for poor customer service. The marketing of the ZX81 was handled by Sinclair's long-standing marketing agency Primary Contact (now part of Ogilvy & Mather ), which had provided marketing services for Sinclair since 1971 and was to continue doing so until 1985. Sinclair's entry into the nascent home computing market gave Primary Contact a major challenge – how to market a product simultaneously at hobbyists and at
1584-487: A simple Sinclair BASIC interpreter . The entire machine weighs just 350 grams (12 oz). Early versions of the external RAM cartridge contain 15 KB of memory using an assortment of memory chips, while later versions contain 16 KB chips with the lowest addressed kilobyte disabled. The front part of the case is occupied by an integrated 40-key membrane keyboard . The keyboard is mechanically very simple, consisting of 40 pressure-pad switches and 8 diodes under
1683-530: A triumph of innovation: "The ZX81 had four chips when our nearest competitor in this respect, the TRS-80, had 44." Only 70% of the logic gates on the ULA were supposed to be used, but Sinclair decided to use them all to squeeze more functions in. This resulted in the machine becoming uncomfortably warm during usage. Computing folklore held that the ZX81 had to be refrigerated by balancing a carton of cold milk on top of
1782-551: A variety of third-party companies make use of this facility to create a wide range of add-ons for the ZX81. The following table provides a comparison between the capabilities of the ZX81 and various other competing microcomputers that were available in June 1981, about the time that the first ZX81 orders were delivered. The prices given are as of June 1981 from Your Computer UK. The Atari 400 and TRS-80 model I were officially only expandable to 16 KB, but expansion to 48 KB
1881-593: Is semi-volatile . The term is used to describe a memory that has some limited non-volatile duration after power is removed, but then data is ultimately lost. A typical goal when using a semi-volatile memory is to provide the high performance and durability associated with volatile memories while providing some benefits of non-volatile memory. For example, some non-volatile memory types experience wear when written. A worn cell has increased volatility but otherwise continues to work. Data locations which are written frequently can thus be directed to use worn circuits. As long as
1980-464: Is a system where each program is given an area of memory to use and is prevented from going outside that range. If the operating system detects that a program has tried to alter memory that does not belong to it, the program is terminated (or otherwise restricted or redirected). This way, only the offending program crashes, and other programs are not affected by the misbehavior (whether accidental or intentional). Use of protected memory greatly enhances both
2079-409: Is also used to describe semi-volatile behavior constructed from other memory types, such as nvSRAM , which combines SRAM and a non-volatile memory on the same chip , where an external signal copies data from the volatile memory to the non-volatile memory, but if power is removed before the copy occurs, the data is lost. Another example is battery-backed RAM , which uses an external battery to power
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#17327937509242178-470: Is computer memory that requires power to maintain the stored information. Most modern semiconductor volatile memory is either static RAM (SRAM) or dynamic RAM (DRAM). DRAM dominates for desktop system memory. SRAM is used for CPU cache . SRAM is also found in small embedded systems requiring little memory. SRAM retains its contents as long as the power is connected and may use a simpler interface, but commonly uses six transistors per bit . Dynamic RAM
2277-452: Is delivered via four sockets on the left side of the case. The machine uses an ordinary UHF television set to deliver a monochrome picture via a built-in RF modulator. It can display 24 lines of 32 characters each, and by using the selection of 2×2 block character graphics from the machine's character set offers an effective 64 × 44 pixel graphics mode, also directly addressable via BASIC using
2376-612: Is determined by a combination of context in the command and mode selection e.g. SHIFT and FUNCTION keys to select the red keyboard functions. For example, the P key combines the letter P , the " character, and the BASIC commands PRINT and TAB . Context mode feedback is displayed by the cursor displaying an inverted letter; The fact that to effect a RUBOUT or backspace/delete operation took 2 key presses encouraged ZX81 programmers to be brief and type carefully when entering text or code. The ZX81's primary input/output
2475-416: Is housed inside a wedge-shaped plastic case measuring 167 millimetres (6.6 in) wide by 40 millimetres (1.6 in) high. The memory is provided by either a single 4118 (1024 bit × 8) or two 2114 (1024 bit × 4) RAM chips. There are only three other onboard chips: a 3.5 MHz Z80A 8-bit microprocessor from NEC , an uncommitted logic array (ULA) chip from Ferranti , and an 8 KB ROM providing
2574-918: Is more complicated for interfacing and control, needing regular refresh cycles to prevent losing its contents, but uses only one transistor and one capacitor per bit, allowing it to reach much higher densities and much cheaper per-bit costs. Non-volatile memory can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory , flash memory , most types of magnetic computer storage devices (e.g. hard disk drives , floppy disks and magnetic tape ), optical discs , and early computer storage methods such as magnetic drum , paper tape and punched cards . Non-volatile memory technologies under development include ferroelectric RAM , programmable metallization cell , Spin-transfer torque magnetic RAM , SONOS , resistive random-access memory , racetrack memory , Nano-RAM , 3D XPoint , and millipede memory . A third category of memory
2673-411: Is organized into memory cells each storing one bit (0 or 1). Flash memory organization includes both one bit per memory cell and a multi-level cell capable of storing multiple bits per cell. The memory cells are grouped into words of fixed word length , for example, 1, 2, 4, 8, 16, 32, 64 or 128 bits. Each word can be accessed by a binary address of N bits, making it possible to store 2 words in
2772-482: Is physically stored or whether the user's computer will have enough memory. The operating system will place actively used data in RAM, which is much faster than hard disks. When the amount of RAM is not sufficient to run all the current programs, it can result in a situation where the computer spends more time moving data from RAM to disk and back than it does accomplishing tasks; this is known as thrashing . Protected memory
2871-432: Is ready for them. The task of designing the ZX81's case again fell to Rick Dickinson, who produced an updated version of the ZX80's wedge-shaped case. This time round, the design team were able to use injection moulding , which enabled them to deliver a higher-quality case. Dickinson originally envisaged the ZX81 as "an expandable range of boxes following a vaguely modular approach with a common width", though this approach
2970-527: Is to a television set rather than a dedicated monitor . Programs and data are loaded and saved onto compact audio cassettes . It uses only four silicon chips and 1 KB of memory . It has no power switch or moving parts, with the exception of a VHF TV channel selector switch present in some models. It has a pressure-sensitive membrane keyboard . The ZX81's limitations prompted a market in third-party peripherals to improve its capabilities. Its distinctive case and keyboard brought designer Rick Dickinson
3069-654: The BBC Micro went to Acorn, which launched the machine in January 1982. Paul Kriwaczek, the producer of The Computer Programme , explained his reservations in a March 1982 interview with Your Computer : I would have been very reluctant for the BBC to sell something like the Sinclair [ZX81] because it is so limited. The Sinclair cannot be expanded; it is fundamentally a throw-away consumer product. Its usefulness lies in learning about programming, but I do not believe that
Timex Sinclair - Misplaced Pages Continue
3168-501: The Electrotechnical Laboratory in 1972. Flash memory was invented by Fujio Masuoka at Toshiba in the early 1980s. Masuoka and colleagues presented the invention of NOR flash in 1984, and then NAND flash in 1987. Toshiba commercialized NAND flash memory in 1987. Developments in technology and economies of scale have made possible so-called very large memory (VLM) computers. Volatile memory
3267-499: The Royal Radar Establishment proposed digital storage systems that use CMOS (complementary MOS) memory cells, in addition to MOSFET power devices for the power supply , switched cross-coupling, switches and delay-line storage . The development of silicon-gate MOS integrated circuit (MOS IC) technology by Federico Faggin at Fairchild in 1968 enabled the production of MOS memory chips . NMOS memory
3366-558: The System/360 Model 95 . Toshiba introduced bipolar DRAM memory cells for its Toscal BC-1411 electronic calculator in 1965. While it offered improved performance, bipolar DRAM could not compete with the lower price of the then dominant magnetic-core memory. MOS technology is the basis for modern DRAM. In 1966, Robert H. Dennard at the IBM Thomas J. Watson Research Center was working on MOS memory. While examining
3465-550: The Whirlwind I computer in 1953. Magnetic-core memory was the dominant form of memory until the development of MOS semiconductor memory in the 1960s. The first semiconductor memory was implemented as a flip-flop circuit in the early 1960s using bipolar transistors . Semiconductor memory made from discrete devices was first shipped by Texas Instruments to the United States Air Force in 1961. In
3564-559: The ZX Printer code into the ROM. Although it was eventually fixed, the bug became the subject of controversy and Sinclair was forced to replace some of the ZX81s sold to early customers. On a more positive note, Vickers' work on the manual was received favourably, being described in 1983 as "one of the classic texts on BASIC". Max Phillips commented in a What Micro? retrospective: It does
3663-487: The rules of chess . The ZX81 conserves its memory to a certain extent by representing entire BASIC commands as one-byte tokens, stored as individual "characters" in the upper reaches of the machine's unique (non- ASCII ) character set . The edge connector or external interface at the rear of the ZX81 is an extension of the main printed circuit board. This provides a set of address, control, and data lines that can be used to communicate with external devices. Enthusiasts and
3762-418: The "man on the street", who probably had little or no computer literacy. The answer was to pursue what the journalist David O'Reilly of MicroScope magazine described as a single-minded "user-friendly strategy." Chris Fawkes, one of Primary Contact's directors, explained: "We brought personal computers to the mass market by showing that you didn't have to be a whizzkid to use one." As Clive Sinclair put it in
3861-561: The Arma Division of the American Bosch Arma Corporation. In 1967, Dawon Kahng and Simon Sze of Bell Labs proposed that the floating gate of a MOS semiconductor device could be used for the cell of a reprogrammable ROM, which led to Dov Frohman of Intel inventing EPROM (erasable PROM) in 1971. EEPROM (electrically erasable PROM) was developed by Yasuo Tarui, Yutaka Hayashi and Kiyoko Naga at
3960-615: The MK14 by producing the ZX80, at the time the world's smallest and cheapest computer, which was launched in January 1980 costing £99.95 (equivalent to £390 at 2021 prices. ) The company conducted no market research whatsoever prior to the launch of the ZX80; according to Clive Sinclair, he "simply had a hunch" that the general public was sufficiently interested to make such a project feasible and went ahead with ordering 100,000 sets of parts so that he could launch at high volume. The ZX80's design introduced many key features that were carried over to
4059-500: The PLOT and UNPLOT commands, leaving 2 lines free at the bottom. Two 3.5 mm jacks connect the ZX81 to the EAR (output) and MIC (input) sockets of an audio cassette recorder, enabling data to be saved or loaded. This stores each data bit as a number of pulses followed by an inter-bit silence of 1300 μs. Each pulse is a 150 μs "high" then a 150 μs "low". A "0" bit consists of four pulses while
Timex Sinclair - Misplaced Pages Continue
4158-582: The T/S 1500 and T/S 2068. Both were more expensive ($ 79 and $ 199 respectively) and with low sales. Timex Sinclair released four computers, all of them based (to some extent) on Sinclair Research's existing machines. In chronological order: Timex Computer Corporation, under the Timex Sinclair brand, and Timex Portugal, under the Timex Computer brand, produced a number of different peripherals for
4257-487: The Timex computer line: Timex Computer Corporation, under the Timex Sinclair brand, released 9 business, 20 home management, 30 education and 25 game titles on cassette for the T/S 1000 and T/S 1500. Four titles on cartridges were also released. For the T/S 2068, 4 business, 13 home management, 29 education and 24 game titles were released on cassette. Seven titles were released on cartridges. Timex Portugal sold/developed
4356-1101: The U.S.. Timex Portugal sold the Timex Sinclair (ex: T/S 2068 ) models in Portugal and Poland under the Timex Computer (ex: TC 2068) brand. In order to market Timex Sinclair products in the United States, Timex Corporation created a subsidiary named "Timex Computer Corporation", and sold machines under the brand Timex Sinclair . Timex Sinclair ended as Timex Corporation withdrew from the U.S. home computer market in January 1984 but Timex Portugal continued to manufacture, sell and develop hardware in Portugal and Poland for another ten years, with some machines also being sold in Canada and Argentina (see Czerweny computers ). A 1986 report mentions that 800.000 systems, between TC 2048 , TC 2068 and FDD3000 , were sold to Poland. Overall, Timex Sinclair machines were nowhere near as successful as their UK progenitors; in contrast with
4455-533: The ZX Spectrum, which was the best-selling computer in Britain at the time, the T/S 2068 was a relative failure, partly due to Timex Corporation leaving the computer business shortly after its introduction. The T/S 1000 was introduced in July 1982, with Timex Sinclair touting it as the first home computer to cost under $ 100 in the U.S. market. In spite of the flaws in the early versions, 550,000 units were sold by
4554-462: The ZX80 and that by the time the series was broadcast there were likely to be upwards of 100,000 ZX81 users. A prototype ZX81 was demonstrated to BBC representatives in January 1981, while Sinclair's local rival Acorn Computers put forward their proposed Proton computer, a design – of which a prototype did not yet exist – based on the Acorn Atom . To Sinclair's dismay, the contract to produce
4653-657: The ZX80 made a follow-up product inevitable. The company was renamed Sinclair Computers in November 1980, reflecting its new focus, and became Sinclair Research in March 1981. The launch of the ZX81 was catalysed in part by the BBC Computer Literacy Project's plan to produce The Computer Programme TV series, to be broadcast in 1982, aimed at popularising computing and programming. The BBC intended to commission an existing manufacturer to provide it with
4752-450: The ZX80's chips into a single uncommitted logic array (ULA) , a type of general-purpose chip full of logic gates that were connected up as the customer required during chip manufacture. This short-lived technology of the day was cheaper and quicker than the design of a customised logic chip, which typically required very high volumes to recoup its development cost. Ferranti produced the new chip for Sinclair, who hailed Westwood's design as
4851-459: The ZX81 concentrates on driving the display. It runs the current program for only about a quarter of the time – in effect slowing the machine down fourfold, although in practice the speed difference between FAST and SLOW modes depends on what computation is being done. In FAST mode, processing occurs continuously, but the display is abandoned to its own devices – equivalent to the ZX80's standard operating mode. Another hardware quirk produced one of
4950-404: The ZX81 got under way even before the ZX80 had been launched. Sinclair's chief engineer, Jim Westwood , was given the task of improving the ZX80's hardware to reduce the number of components and thus bring down the cost. He also sought to fix some of the more annoying problems with the ZX80. Westwood and his colleagues found that the component count could be reduced greatly by combining eighteen of
5049-510: The ZX81 manual as the " dogsbody " of the system, has a number of key functions that competing computers share between multiple chips and integrated circuits. These comprise the following: The ZX81's built-in RF modulator can output a video picture to a UHF 625-line television (used in the UK, Australia, and most western European countries). France and Luxembourg required a slightly modified version of
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#17327937509245148-649: The ZX81 was controversial. W.H. Smith, one of the machine's key distributors, had a company policy of ordering a third more ZX81s than were actually required for sale, so that it would have enough replacements for faulty machines. Similar problems were reported in the US market, where contemporary reports suggested that only a third of the ZX81s shipped actually worked. However, figures released by Sinclair claimed that only 2.4 per cent of pre-assembled machines were returned, although 13 per cent of kits were returned. Clive Sinclair strongly denied any problem with reliability: We have
5247-416: The ZX81 was released, ZX80 owners were able to upgrade by the relatively simple expedient of plugging a new ROM onto the circuit board. The ZX80 was an immediate success, selling 20,000 units over the following nine months. Science of Cambridge was producing ZX80s at the rate of 9,000 a month by the end of 1980 and within 18 months of its launch the company had sold 100,000 units. The commercial success of
5346-481: The ZX81's more novel features, a syntax checker that indicated errors in BASIC code as soon as it was entered (rather than, as was standard at the time, only disclosing coding errors when a program was run). Unfortunately for Vickers, he introduced a briefly notorious error – the so-called "square-root bug" that caused the square root of 0.25 to be returned erroneously as 1.3591409 – as a result of problems with integrating
5445-508: The ZX81; as Sinclair himself later said, "the ZX80 was very much a stepping stone to the ZX81". The design was driven entirely by the desired price – the machine had to cost less than £100 but still make a healthy profit. Its distinctive wedge-shaped white case concealing the circuitry and the touch-sensitive membrane keyboard were the brainchild of Rick Dickinson , a young British industrial designer who had recently been hired by Sinclair. As he later recalled of Sinclair's approach, "Everything
5544-428: The calculator market following the launch of a new generation of Japanese-produced calculators with liquid-crystal displays , which were much more capable and power-efficient than Sinclair's LED calculators. Projects to develop a pocket television and digital watch turned out to be expensive failures. The company made losses of more than £350,000 in 1975–76, bringing it to the edge of bankruptcy. In July 1977 Radionics
5643-463: The case, there were many more similarities with the ZX81. Like its successor, it used the Z80A microprocessor and had only 1 KB of on-board RAM. It came with a specially written BASIC interpreter on a dedicated ROM chip and could use a television as a display. It relied on an ordinary cassette tape recorder for data storage. The main difference between the two machines lay in the internal software; when
5742-494: The case. The ZX81's ROM was doubled to 8 KB, from the ZX80's 4 KB ROM. This enabled a fuller implementation of a version of ANSI Minimal BASIC (termed Sinclair BASIC by the company). Clive Sinclair re-commissioned a company called Nine Tiles, which had produced the ZX80 ROM, to develop the new ROM software for the ZX81. The code was written by John Grant, the owner of Nine Tiles, and Steve Vickers , who had joined
5841-490: The characteristics of MOS technology, he found it was possible to build capacitors , and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while the MOS transistor could control writing the charge to the capacitor. This led to his development of a single-transistor DRAM memory cell. In 1967, Dennard filed a patent for a single-transistor DRAM memory cell based on MOS technology. This led to
5940-406: The company had little previous experience in assembling electronics. It was a well-established manufacturer of mechanical watches but was facing a crisis at the beginning of the 1980s. Profits had dwindled to virtually zero as the market for mechanical watches stagnated in the face of competition from the digital and quartz watches. Recognising the trend, Timex's director, Fred Olsen , determined that
6039-423: The company in January 1980. Grant concentrated on the software that drove the ZX81's hardware, while Vickers developed the new BASIC and the accompanying manual. Sinclair's brief to the pair was fairly non-specific but primarily concerned remedying a key defect of the ZX80 so that the new machine could be used for practical programming and calculations. Vickers later recalled: As far as Clive was concerned, it wasn't
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#17327937509246138-462: The company would diversify into other areas of business. This shift by Timex came at an ideal time for Sinclair. The ZX80 had proved more popular than expected and Sinclair's existing manufacturer, a small electronics company in St Ives , lacked the resources to deal with the demand. Timex took over production of the ZX80 late in 1980. The arrangement worked well for both companies and Timex took on
6237-714: The computer memory can be transferred to storage; a common way of doing this is through a memory management technique called virtual memory . Modern computer memory is implemented as semiconductor memory , where data is stored within memory cells built from MOS transistors and other components on an integrated circuit . There are two main kinds of semiconductor memory: volatile and non-volatile . Examples of non-volatile memory are flash memory and ROM , PROM , EPROM , and EEPROM memory. Examples of volatile memory are dynamic random-access memory (DRAM) used for primary storage and static random-access memory (SRAM) used mainly for CPU cache . Most semiconductor memory
6336-597: The delay line, the Williams tube and Selectron tube , originated in 1946, both using electron beams in glass tubes as means of storage. Using cathode-ray tubes , Fred Williams invented the Williams tube, which was the first random-access computer memory . The Williams tube was able to store more information than the Selectron tube (the Selectron was limited to 256 bits, while the Williams tube could store thousands) and
6435-401: The early 1940s. Through the construction of a glass tube filled with mercury and plugged at each end with a quartz crystal, delay lines could store bits of information in the form of sound waves propagating through the mercury, with the quartz crystals acting as transducers to read and write bits. Delay-line memory was limited to a capacity of up to a few thousand bits. Two alternatives to
6534-464: The end of the year. In 1983, about 100,000 units were sold in Canada, and 400,000 in the US, with the price dropping to $ 49.95. A new computer was announced in May. Named T/S 2000, it was based on the ZX Spectrum, and would come in with 16 or 48K RAM versions, costing $ 150 or $ 200. The 16K version was cancelled, and the 48K version was released as T/S 2068. Two new computers were introduced that same year,
6633-594: The first commercial DRAM IC chip, the Intel 1103 in October 1970. Synchronous dynamic random-access memory (SDRAM) later debuted with the Samsung KM48SL2000 chip in 1992. The term memory is also often used to refer to non-volatile memory including read-only memory (ROM) through modern flash memory . Programmable read-only memory (PROM) was invented by Wen Tsing Chow in 1956, while working for
6732-466: The following software, under the Timex Computer brand: Sinclair ZX81 The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee , Scotland, by Timex Corporation . It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and designed to be a low-cost introduction to home computing for the general public. It
6831-518: The following types: Virtual memory is a system where physical memory is managed by the operating system typically with assistance from a memory management unit , which is part of many modern CPUs . It allows multiple types of memory to be used. For example, some data can be stored in RAM while other data is stored on a hard drive (e.g. in a swapfile ), functioning as an extension of the cache hierarchy . This offers several advantages. Computer programmers no longer need to worry about where their data
6930-486: The future of computers lies in everyone learning to program in BASIC. Sinclair was critical of the BBC's decision, accusing it of incompetence and arrogance. Shortly after Acorn won the BBC contract the Government issued a recommended list of computers, including the BBC Micro and Research Machines 380Z , that schools could purchase, with the aid of a grant, for half price; Sinclair's computers were not included on
7029-769: The higher failure rate of the kits to customers breaking the components by inserting or soldering them the wrong way, though the company admitted that there was a persistent problem with power supplies that affected both kits and pre-assembled ZX81s. The bigger problem was perhaps Sinclair's lack of after-sales service, which Robin Clarke of New Scientist described as "one of the worst after-sales performance records of any company ever established." The Financial Times observed that "Clive Sinclair's offices are filled with returned computers which can take months to be repaired." The company's slowness in replacing returns and delivering freshly ordered machines meant that Sinclair Research gained
7128-466: The instrument side of the business, which was virtually the only area where Radionics was profitable. Sinclair disagreed vehemently with what he characterised as the view "that there was no future in consumer electronics". This and other disputes led to Sinclair resigning from Radionics in July 1979. While he was struggling with the NEB, Clive Sinclair turned to a "corporate lifeboat" in the shape of an existing corporate shell under his exclusive control –
7227-449: The late 1960s. The invention of the metal–oxide–semiconductor field-effect transistor ( MOSFET ) enabled the practical use of metal–oxide–semiconductor (MOS) transistors as memory cell storage elements. MOS memory was developed by John Schmidt at Fairchild Semiconductor in 1964. In addition to higher performance, MOS semiconductor memory was cheaper and consumed less power than magnetic core memory. In 1965, J. Wood and R. Ball of
7326-417: The launch of the ZX81, that the delivery times finally came down to the promised twenty-eight days. Those who already owned or had recently ordered the ZX80 were not excluded; anyone who had ordered a ZX80 in the two weeks before the ZX81's launch would receive the newer machine, while existing owners were able to upgrade their ZX80s by plugging an extra £20 ROM chip into the circuit board. The reliability of
7425-458: The list. Sinclair responded by launching his own half-price deal, offering schools the chance to buy a ZX81 and 16 KB RAM pack for £60, plus a ZX Printer at half price, for a total cost of £90. As the cheapest Government-approved system was £130, this was an attractive offer for some schools and about 2,300 bought Sinclair's package, although 85% adopted the BBC Micro. The development of
7524-447: The location is updated within some known retention time, the data stays valid. After a period of time without update, the value is copied to a less-worn circuit with longer retention. Writing first to the worn area allows a high write rate while avoiding wear on the not-worn circuits. As a second example, an STT-RAM can be made non-volatile by building large cells, but doing so raises the cost per bit and power requirements and reduces
7623-426: The machine to match the positive video modulation of CCIR System L sets, while the United States and Canada required a different ULA chip and modulator to cope with their 525-line VHF ( NTSC ) television systems. Both the ZX81 and its predecessor, the ZX80, have a significant drawback in the way that they handle visual output. Neither machine has enough processing power to run at full speed and simultaneously maintain
7722-409: The manufacture of the ZX81, aided by capital investment in its Dundee plant. Sinclair initially planned to produce 10,000 ZX81s a month, rising to 30,000 a month within a year. However, Timex initially had significant problems in producing enough ZX81s to satisfy demand. As a consequence, it took up to nine weeks for ZX81s to be delivered by mail order. It was not until September 1981, five months after
7821-457: The memory device in case of external power loss. If power is off for an extended period of time, the battery may run out, resulting in data loss. Proper management of memory is vital for a computer system to operate properly. Modern operating systems have complex systems to properly manage memory. Failure to do so can lead to bugs or slow performance. Improper management of memory is a common cause of bugs and security vulnerabilities, including
7920-478: The memory. In the early 1940s, memory technology often permitted a capacity of a few bytes. The first electronic programmable digital computer , the ENIAC , using thousands of vacuum tubes , could perform simple calculations involving 20 numbers of ten decimal digits stored in the vacuum tubes. The next significant advance in computer memory came with acoustic delay-line memory , developed by J. Presper Eckert in
8019-455: The most distinctive aspects of the ZX81's screen display – during loading or saving, moving zigzag stripes appear across the screen. The same pin on the ULA is used to handle the video signal and the tape output, producing the stripes as an interference pattern of sorts. The ULA cannot maintain the display during SAVE and LOAD operations, as it has to operate continuously to maintain the correct baud rate for data transfers. The interference produces
8118-409: The reliability and security of a computer system. Without protected memory, it is possible that a bug in one program will alter the memory used by another program. This will cause that other program to run off of corrupted memory with unpredictable results. If the operating system's memory is corrupted, the entire computer system may crash and need to be rebooted . At times programs intentionally alter
8217-455: The rest of the business", specifically the development of the ultimately unsuccessful TV80 pocket television and C5 electric vehicle. In an interview with Practical Computing , Sinclair explained: I make computers because they are a good market, and they are interesting to design. I don't feel bad about making them or selling them for money or anything, there is a demand for them and they do no harm; but I don't think they are going to save
8316-521: The same figure in pounds sterling by the time it has reached the shores of Britain". Off-the-shelf personal computers were also available for the high end of the market but were extremely expensive; Olivetti's offering cost £2,000, and the Commodore PET, launched in 1979, sold for £700. There was nothing for the hobbyist at the low end of the market. Sinclair realised that this provided a useful commercial opportunity. Sinclair's first home computer
8415-479: The same year, the concept of solid-state memory on an integrated circuit (IC) chip was proposed by applications engineer Bob Norman at Fairchild Semiconductor . The first bipolar semiconductor memory IC chip was the SP95 introduced by IBM in 1965. While semiconductor memory offered improved performance over magnetic-core memory, it remained larger and more expensive and did not displace magnetic-core memory until
8514-405: The screen display. On the ZX80, this means that the screen goes blank every time the machine carries out a computation and causes an irritating flicker whenever a shorter computation – such as processing a keystroke – takes place. The ZX81's designers adopted an improved approach, involving the use of two modes called SLOW and FAST respectively. In SLOW mode, also called "compute and display" mode,
8613-536: The street would want such a computer. He does, and our information is that a lot of people are using the machines avidly." A New Scientist retrospective published in 1986 commented: Computer memory Computer memory stores information, such as data and programs, for immediate use in the computer . The term memory is often synonymous with the terms RAM , main memory , or primary storage . Archaic synonyms for main memory include core (for magnetic core memory) and store . Main memory operates at
8712-515: The world. By the late 1970s, American companies were producing simple home computer kits such as the MITS Altair and IMSAI 8080 . This aroused interest among electronics hobbyists in the UK but relatively high prices and lower disposable income reduced the appeal of the American products. New Scientist stated in 1977 that "the price of an American kit in dollars rapidly translates into
8811-434: The write speed. Using small cells improves cost, power, and speed, but leads to semi-volatile behavior. In some applications, the increased volatility can be managed to provide many benefits of a non-volatile memory, for example by removing power but forcing a wake-up before data is lost; or by caching read-only data and discarding the cached data if the power-off time exceeds the non-volatile threshold. The term semi-volatile
8910-546: The zigzag stripes. The unexpanded ZX81's tiny memory presents a major challenge to programmers. Simply displaying a full screen takes up to 793 bytes, the system variables take up another 125 bytes, and the program, input buffer and stacks need more memory on top of that. Nonetheless, ingenious programmers are able to achieve a surprising amount with just 1 KB. One example is the Super Micro Chess Engine by Stefano Maragò, which includes all of
9009-440: Was available from third-party suppliers. Clive Sinclair, a former radio kit salesman, established his first company, Sinclair Radionics , in 1962. The company made its name producing a wide range of cheap electronics aimed at the hobbyist market. Its products include amplifiers , radios, multimeters and other items which were generally sold in kit form to hi-fi enthusiasts and other electronics hobbyists. The company entered
9108-638: Was commercialized by IBM in the early 1970s. MOS memory overtook magnetic core memory as the dominant memory technology in the early 1970s. The two main types of volatile random-access memory (RAM) are static random-access memory (SRAM) and dynamic random-access memory (DRAM). Bipolar SRAM was invented by Robert Norman at Fairchild Semiconductor in 1963, followed by the development of MOS SRAM by John Schmidt at Fairchild in 1964. SRAM became an alternative to magnetic-core memory, but requires six transistors for each bit of data. Commercial use of SRAM began in 1965, when IBM introduced their SP95 SRAM chip for
9207-419: Was cost driven. The design was the face of the machine." The unconventional keyboard was the outcome of Sinclair's cost-cutting. It made use of a sheet of plastic, on which the keys were printed, overlaying a metallic circuit that registered when a key was pressed. This avoided the expense of providing a typewriter-style keyboard, though the design had many drawbacks when it came to usability and "feel". Inside
9306-462: Was eventually dropped. From start to finish, the design process took about six months. The ZX81 was launched on 5 March 1981 in two versions (though with identical components) – a pre-assembled machine or a cheaper kit version, which the user could assemble themself. Both versions were manufactured in Dundee , Scotland by Timex Corporation at the company's Dryburgh factory. Timex had not been an obvious choice of manufacturing subcontractor, as
9405-539: Was hugely successful; more than 1.5 million units were sold. In the United States it was initially sold as the ZX-81 under licence by Timex. Timex later produced its own versions of the ZX81: the Timex Sinclair 1000 and Timex Sinclair 1500 . Unauthorized ZX81 clones were produced in several countries. The ZX81 was designed to be small, simple, and above all, inexpensive, with as few components as possible. Video output
9504-421: Was less expensive. The Williams tube was nevertheless frustratingly sensitive to environmental disturbances. Efforts began in the late 1940s to find non-volatile memory . Magnetic-core memory allowed for memory recall after power loss. It was developed by Frederick W. Viehe and An Wang in the late 1940s, and improved by Jay Forrester and Jan A. Rajchman in the early 1950s, before being commercialized with
9603-488: Was rescued by a state agency, the National Enterprise Board (NEB), which recapitalised it, provided a loan facility and took effective control of the company by acquiring a 73% stake. Clive Sinclair's relationship with the NEB was fraught due to conflicting notions about which direction the company should go. Radionics had begun a project to develop a home computer but the NEB wanted to concentrate on
9702-593: Was the MK14 , which was launched in kit form in June 1978. It was a long way from being a mass-market product. Its very name – MK standing for "Microcomputer Kit" – was indicative of its origins as a product developed by, and for, hobbyists. It had no screen but instead used an LED segment display (though Science of Cambridge did produce an add-on module allowing it to be hooked up to a UHF TV); it had no case, consisting of an exposed circuit board; it had no built-in storage capabilities and only 256 bytes of memory; and input
9801-406: Was via a 20-key hexadecimal keyboard. Despite the limitations of the machine it sold a respectable 10–15,000 units; by comparison, the much more expensive Apple II had only sold 9,000 units in the United States, a much bigger market, in 1978. This success convinced Clive Sinclair that there was an untapped market for low-cost computers that could profitably be exploited. Sinclair followed up
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