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84-453: The history of Nascom starts with the history of John A. Marshall. Marshall was the "& Son" of "A Marshall & Son (London) Ltd", an electronic component retailer whose adverts were a regular feature in hobby electronics magazines from as early as 1967. Marshall was a director of a company called Nasco Sales Ltd; a UK distributor of US semiconductors . He was also connected with a company called Lynx Electronics (London) Ltd. which had been

168-440: A current requires the flow of electrons, and semiconductors have their valence bands filled, preventing the entire flow of new electrons. Several developed techniques allow semiconducting materials to behave like conducting materials, such as doping or gating . These modifications have two outcomes: n-type and p-type . These refer to the excess or shortage of electrons, respectively. A balanced number of electrons would cause

252-439: A cut-off frequency of one cycle per second, too low for any practical applications, but an effective application of the available theory. At Bell Labs , William Shockley and A. Holden started investigating solid-state amplifiers in 1938. The first p–n junction in silicon was observed by Russell Ohl about 1941 when a specimen was found to be light-sensitive, with a sharp boundary between p-type impurity at one end and n-type at

336-472: A "hobby" purchase. At the end of 1976, Marshall attended a microprocessor seminar at Imperial College and met Phil Pitman. Pitman was the marketing manager for Mostek, which had recently become a second source for Zilog's Z80 processor. Pitman put Marshall in touch with a design consultant named Chris Shelton and, in the spring of 1977, Marshall commissioned Shelton Instruments to design the Nascom 1. Most of

420-450: A "snow plough" design that reduced the effect by blanking the video when simultaneous access occurred. The Nascom 2 used a slightly different design but still allowed contention to occur, this time giving rise to black flicker (blanking) on the screen. Initially, users were expected to write their own software. On the earliest machines with limited memory this meant writing Z80 assembly language on paper, assembling it by hand and then using

504-535: A 16-pin IC-style DIL socket at each end of the connection from the keyboard to the computer main board. The Nascom 2 used a 0.1" 2x8 male header (16 pins total) at each end. In each case, the connectors use the same physical ordering of signals but the pin numbers do not correspond (because DIL sockets and IDC headers use different numbering conventions). The Nascom 2 keyboard has an additional "sense" output. Both Nascom 1 and Nascom 2 main boards had connections to

588-513: A common semi-insulator is gallium arsenide . Some materials, such as titanium dioxide , can even be used as insulating materials for some applications, while being treated as wide-gap semiconductors for other applications. The partial filling of the states at the bottom of the conduction band can be understood as adding electrons to that band. The electrons do not stay indefinitely (due to the natural thermal recombination ) but they can move around for some time. The actual concentration of electrons

672-423: A completely full valence band is inert, not conducting any current. If an electron is taken out of the valence band, then the trajectory that the electron would normally have taken is now missing its charge. For the purposes of electric current, this combination of the full valence band, minus the electron, can be converted into a picture of a completely empty band containing a positively charged particle that moves in

756-521: A crude, blocky 96×48 graphics display. Each character was 8 pixels wide and 16 pixels high, allowing display of true descenders . Therefore, a character occupied 16 bytes in the ROM (so that 256 characters required a total of 256*16=4Kbytes of character generator storage). Characters were abutted vertically and horizontally on the display and so the design of the characters within the character generator included vertical and horizontal inter-character spacing. On

840-474: A current to flow throughout the material. Homojunctions occur when two differently doped semiconducting materials are joined. For example, a configuration could consist of p-doped and n-doped germanium . This results in an exchange of electrons and holes between the differently doped semiconducting materials. The n-doped germanium would have an excess of electrons, and the p-doped germanium would have an excess of holes. The transfer occurs until an equilibrium

924-410: A guide to the construction of more capable and reliable devices. Alexander Graham Bell used the light-sensitive property of selenium to transmit sound over a beam of light in 1880. A working solar cell, of low efficiency, was constructed by Charles Fritts in 1883, using a metal plate coated with selenium and a thin layer of gold; the device became commercially useful in photographic light meters in

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1008-445: A low-pressure chamber to create plasma . A common etch gas is chlorofluorocarbon , or more commonly known Freon . A high radio-frequency voltage between the cathode and anode is what creates the plasma in the chamber. The silicon wafer is located on the cathode, which causes it to be hit by the positively charged ions that are released from the plasma. The result is silicon that is etched anisotropically . The last process

1092-466: A metal frame that was riveted to a single-sided fibreglass PCB . The frame improves reliability by preventing the force of repeated keystrokes from being transmitted to the solder joints that connect the key switches to the PCB. A separate, conventional, key switch was provided on the keyboard for hardware reset. The Nascom 1 had 47 keys. The Nascom 2 had 10 additional keys (GRAPH, which toggled bit 7, CTRL,

1176-626: A non-equilibrium situation. This introduces electrons and holes to the system, which interact via a process called ambipolar diffusion . Whenever thermal equilibrium is disturbed in a semiconducting material, the number of holes and electrons changes. Such disruptions can occur as a result of a temperature difference or photons , which can enter the system and create electrons and holes. The processes that create or annihilate electrons and holes are called generation and recombination, respectively. In certain semiconductors, excited electrons can relax by emitting light instead of producing heat. Controlling

1260-519: A pair is completed. Such carrier traps are sometimes purposely added to reduce the time needed to reach the steady-state. The conductivity of semiconductors may easily be modified by introducing impurities into their crystal lattice . The process of adding controlled impurities to a semiconductor is known as doping . The amount of impurity, or dopant, added to an intrinsic (pure) semiconductor varies its level of conductivity. Doped semiconductors are referred to as extrinsic . By adding impurity to

1344-531: A regular advertiser in the hobby electronics press since 1976. During a business trip to California in the Autumn of 1976, Marshall attended an amateur computer club meeting at Stanford University . On the flight home, he started to wonder whether there was a market in the UK for a kit computer. Marshall used the price of an SLR camera (about £200) as a reference point for the amount someone might be prepared to spend on

1428-413: A second SHIFT key, 4 cursor direction keys, LF/CH and keys for [ and ]). The Nascom 2 keyboard was designed to be mounted at an angle; it had angled key-caps which were horizontal when the keyboard itself was mounted at an angle. The key-caps on the Nascom 1 were not angled (see photo). The keyboard was always supplied assembled, even when the rest of the Nascom was supplied as a kit. The Nascom 1 used

1512-501: A silicon atom in the crystal, a vacant state (an electron "hole") is created, which can move around the lattice and function as a charge carrier. Group V elements have five valence electrons, which allows them to act as a donor; substitution of these atoms for silicon creates an extra free electron. Therefore, a silicon crystal doped with boron creates a p-type semiconductor whereas one doped with phosphorus results in an n-type material. During manufacture , dopants can be diffused into

1596-783: A theory of solid-state physics , which developed greatly in the first half of the 20th century. In 1878 Edwin Herbert Hall demonstrated the deflection of flowing charge carriers by an applied magnetic field, the Hall effect . The discovery of the electron by J.J. Thomson in 1897 prompted theories of electron-based conduction in solids. Karl Baedeker , by observing a Hall effect with the reverse sign to that in metals, theorized that copper iodide had positive charge carriers. Johan Koenigsberger  [ de ] classified solid materials like metals, insulators, and "variable conductors" in 1914 although his student Josef Weiss already introduced

1680-476: A vacuum, though with a different effective mass . Because the electrons behave like an ideal gas, one may also think about conduction in very simplistic terms such as the Drude model , and introduce concepts such as electron mobility . For partial filling at the top of the valence band, it is helpful to introduce the concept of an electron hole . Although the electrons in the valence band are always moving around,

1764-567: A variety of proportions. These compounds share with better-known semiconductors the properties of intermediate conductivity and a rapid variation of conductivity with temperature, as well as occasional negative resistance . Such disordered materials lack the rigid crystalline structure of conventional semiconductors such as silicon. They are generally used in thin film structures, which do not require material of higher electronic quality, being relatively insensitive to impurities and radiation damage. Almost all of today's electronic technology involves

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1848-415: Is a combination of processes that are used to prepare semiconducting materials for ICs. One process is called thermal oxidation , which forms silicon dioxide on the surface of the silicon . This is used as a gate insulator and field oxide . Other processes are called photomasks and photolithography . This process is what creates the patterns on the circuit in the integrated circuit. Ultraviolet light

1932-547: Is a critical element for fabricating most electronic circuits . Semiconductor devices can display a range of different useful properties, such as passing current more easily in one direction than the other, showing variable resistance, and having sensitivity to light or heat. Because the electrical properties of a semiconductor material can be modified by doping and by the application of electrical fields or light, devices made from semiconductors can be used for amplification, switching, and energy conversion . The term semiconductor

2016-472: Is a function of the temperature, as the probability of getting enough thermal energy to produce a pair increases with temperature, being approximately exp(− E G / kT ) , where k is the Boltzmann constant , T is the absolute temperature and E G is bandgap. The probability of meeting is increased by carrier traps – impurities or dislocations which can trap an electron or hole and hold it until

2100-453: Is a material that is between the conductor and insulator in ability to conduct electrical current. In many cases their conducting properties may be altered in useful ways by introducing impurities (" doping ") into the crystal structure . When two differently doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers , which include electrons , ions , and electron holes , at these junctions

2184-428: Is also used to describe materials used in high capacity, medium- to high-voltage cables as part of their insulation, and these materials are often plastic XLPE ( Cross-linked polyethylene ) with carbon black. The conductivity of silicon is increased by adding a small amount (of the order of 1 in 10 ) of pentavalent ( antimony , phosphorus , or arsenic ) or trivalent ( boron , gallium , indium ) atoms. This process

2268-404: Is called diffusion . This is the process that gives the semiconducting material its desired semiconducting properties. It is also known as doping . The process introduces an impure atom to the system, which creates the p–n junction . To get the impure atoms embedded in the silicon wafer, the wafer is first put in a 1,100 degree Celsius chamber. The atoms are injected in and eventually diffuse with

2352-780: Is inert, blocking the passage of other electrons via that state. The energies of these quantum states are critical since a state is partially filled only if its energy is near the Fermi level (see Fermi–Dirac statistics ). High conductivity in material comes from it having many partially filled states and much state delocalization. Metals are good electrical conductors and have many partially filled states with energies near their Fermi level. Insulators , by contrast, have few partially filled states, their Fermi levels sit within band gaps with few energy states to occupy. Importantly, an insulator can be made to conduct by increasing its temperature: heating provides energy to promote some electrons across

2436-418: Is known as doping, and the resulting semiconductors are known as doped or extrinsic semiconductors . Apart from doping, the conductivity of a semiconductor can be improved by increasing its temperature. This is contrary to the behavior of a metal, in which conductivity decreases with an increase in temperature. The modern understanding of the properties of a semiconductor relies on quantum physics to explain

2520-845: Is neither a very good insulator nor a very good conductor. However, one important feature of semiconductors (and some insulators, known as semi-insulators ) is that their conductivity can be increased and controlled by doping with impurities and gating with electric fields. Doping and gating move either the conduction or valence band much closer to the Fermi level and greatly increase the number of partially filled states. Some wider-bandgap semiconductor materials are sometimes referred to as semi-insulators . When undoped, these have electrical conductivity nearer to that of electrical insulators, however they can be doped (making them as useful as semiconductors). Semi-insulators find niche applications in micro-electronics, such as substrates for HEMT . An example of

2604-404: Is reached by a process called recombination , which causes the migrating electrons from the n-type to come in contact with the migrating holes from the p-type. The result of this process is a narrow strip of immobile ions , which causes an electric field across the junction. A difference in electric potential on a semiconducting material would cause it to leave thermal equilibrium and create

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2688-413: Is the basis of diodes , transistors , and most modern electronics . Some examples of semiconductors are silicon , germanium , gallium arsenide , and elements near the so-called " metalloid staircase " on the periodic table . After silicon, gallium arsenide is the second-most common semiconductor and is used in laser diodes , solar cells , microwave-frequency integrated circuits , and others. Silicon

2772-504: Is typically very dilute, and so (unlike in metals) it is possible to think of the electrons in the conduction band of a semiconductor as a sort of classical ideal gas , where the electrons fly around freely without being subject to the Pauli exclusion principle . In most semiconductors, the conduction bands have a parabolic dispersion relation , and so these electrons respond to forces (electric field, magnetic field, etc.) much as they would in

2856-402: Is used along with a photoresist layer to create a chemical change that generates the patterns for the circuit. The etching is the next process that is required. The part of the silicon that was not covered by the photoresist layer from the previous step can now be etched. The main process typically used today is called plasma etching . Plasma etching usually involves an etch gas pumped in

2940-532: The Annalen der Physik und Chemie in 1835; Rosenschöld's findings were ignored. Simon Sze stated that Braun's research was the earliest systematic study of semiconductor devices. Also in 1874, Arthur Schuster found that a copper oxide layer on wires had rectification properties that ceased when the wires are cleaned. William Grylls Adams and Richard Evans Day observed the photovoltaic effect in selenium in 1876. A unified explanation of these phenomena required

3024-429: The Pauli exclusion principle ). These states are associated with the electronic band structure of the material. Electrical conductivity arises due to the presence of electrons in states that are delocalized (extending through the material), however in order to transport electrons a state must be partially filled , containing an electron only part of the time. If the state is always occupied with an electron, then it

3108-454: The Siege of Leningrad after successful completion. In 1926, Julius Edgar Lilienfeld patented a device resembling a field-effect transistor , but it was not practical. R. Hilsch  [ de ] and R. W. Pohl  [ de ] in 1938 demonstrated a solid-state amplifier using a structure resembling the control grid of a vacuum tube; although the device displayed power gain, it had

3192-445: The band gap , be accompanied by the emission of thermal energy (in the form of phonons ) or radiation (in the form of photons ). In some states, the generation and recombination of electron–hole pairs are in equipoise. The number of electron-hole pairs in the steady state at a given temperature is determined by quantum statistical mechanics . The precise quantum mechanical mechanisms of generation and recombination are governed by

3276-470: The conservation of energy and conservation of momentum . As the probability that electrons and holes meet together is proportional to the product of their numbers, the product is in the steady-state nearly constant at a given temperature, providing that there is no significant electric field (which might "flush" carriers of both types, or move them from neighbor regions containing more of them to meet together) or externally driven pair generation. The product

3360-580: The "nm" logo. In September 1979, PCW reported that Grovewood Securities had invested £500,000 in Nascom. The same article reported that PAL full-colour support would arrive for the Nascom by "the new year". In September 1979, the Nascom 2 (kit) was announced with a list price of £295 + VAT . Then, Nascom were hit by a shortage of Mostek MK4118 1Kx8 RAM devices. 10 devices were required per Nascom 2 (1 each for video RAM and workspace RAM respectively, 8 for user RAM) but Nascom were only able to source 5,000 parts. By November 1979 Nascom had decided to relaunch

3444-461: The 1930s. Point-contact microwave detector rectifiers made of lead sulfide were used by Jagadish Chandra Bose in 1904; the cat's-whisker detector using natural galena or other materials became a common device in the development of radio . However, it was somewhat unpredictable in operation and required manual adjustment for best performance. In 1906, H.J. Round observed light emission when electric current passed through silicon carbide crystals,

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3528-425: The Nascom 1, all 16 rows of the character were displayed, so that the whole image occupied 16*16=256 rows. On the Nascom 2, the top 12 or 14 rows of the character were displayed (controlled by the setting of a switch/jumper on the main board). The 12-row setting was intended for 525 line displays in 60 Hz geographies and the 14-row setting was intended for 625-line displays in 50 Hz geographies. The design of

3612-404: The Nascom 1: The Nascom 1 used DIL sockets for making external connections. The photo shows 4 sockets, used for keyboard, serial (cassette and/or teletype/printer), PIO port A, PIO port B. The small "daughterboard" is a home-made implementation of the "snow plough" circuit referred to below. The I/O address map was decoded as follows: On an unexpanded system, these 8 ports were repeated through

3696-400: The Nascom 2 board could also be configured to accommodate ROMs), wired to accept a 5V 2716 2 KB device. Nascom 2 kits were initially provided with NAS-SYS 1 in masked ROM (the photo shows that at least two date-codes exist for these ROMs). NAS-SYS 1 was the only Nascom monitor ROM to be supplied as masked ROM; all other versions were supplied as EPROMs. Semiconductors A semiconductor

3780-435: The ROM monitor. An annotated disassembly listing of the Nascom 2 Microsoft ROM BASIC was published and the code was subsequently re-purposed in retrocomputing projects such as Grant Searle's Multicomp and Spencer Owen's RC2014. The source code can now be found on GitHub . The Nascom 1 and Nascom 2 hardware designs had these features in common: The I/O address map was common between the Nascom 1 and Nascom 2 designs, and

3864-416: The band gap, inducing partially filled states in both the band of states beneath the band gap ( valence band ) and the band of states above the band gap ( conduction band ). An (intrinsic) semiconductor has a band gap that is smaller than that of an insulator and at room temperature, significant numbers of electrons can be excited to cross the band gap. A pure semiconductor, however, is not very useful, as it

3948-419: The company to start a new business, Gemini Computers. Nascom continued to trade in receivership. In July 1981, PCW reported that Nascom had been bought by Lucas Industries ; the same issue contained a full-page advert under the name "Nascom Microcomputers. Division of Lucas Logic Ltd". In December 1981, the Nascom 3 was launched. This was basically a cased Nascom 2 with some expansion boards. In June 1984,

4032-406: The concentration and regions of p- and n-type dopants. A single semiconductor device crystal can have many p- and n-type regions; the p–n junctions between these regions are responsible for the useful electronic behavior. Using a hot-point probe , one can determine quickly whether a semiconductor sample is p- or n-type. A few of the properties of semiconductor materials were observed throughout

4116-489: The concept of band gaps had been developed. Walter H. Schottky and Nevill Francis Mott developed models of the potential barrier and of the characteristics of a metal–semiconductor junction . By 1938, Boris Davydov had developed a theory of the copper-oxide rectifier, identifying the effect of the p–n junction and the importance of minority carriers and surface states. Agreement between theoretical predictions (based on developing quantum mechanics) and experimental results

4200-566: The details of the Nascom design were described in a series of articles by Pitman that appeared in Wireless World between November 1977 and January 1979. By July 1977, monthly magazine adverts by Lynx Electronics were starting to hint about a microprocessor seminar in the autumn and a forthcoming computer product. On Saturday, 26 November 1977, Lynx Electronics launched the Nascom 1 at their "Home Microcomputer Symposium" at Wembley Conference Centre , London . Tickets cost £3.50 and hosting

4284-453: The electrical properties of materials. The properties of the time-temperature coefficient of resistance, rectification, and light-sensitivity were observed starting in the early 19th century. Thomas Johann Seebeck was the first to notice that semiconductors exhibit special feature such that experiment concerning an Seebeck effect emerged with much stronger result when applying semiconductors, in 1821. In 1833, Michael Faraday reported that

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4368-530: The electrons in the conduction band). When ionizing radiation strikes a semiconductor, it may excite an electron out of its energy level and consequently leave a hole. This process is known as electron-hole pair generation . Electron-hole pairs are constantly generated from thermal energy as well, in the absence of any external energy source. Electron-hole pairs are also apt to recombine. Conservation of energy demands that these recombination events, in which an electron loses an amount of energy larger than

4452-453: The event on a Saturday pitched it at an amateur/hobbyist rather than a professional audience. The event included a raffle for a Nascom 1 computer kit. About 550 people attended the symposium and over 300 kits were sold in the two weeks following the launch. The symposium was covered in detail in Issue 1 of PCW magazine and the Nascom 1 was the cover photograph for that issue (though not with

4536-514: The fast response of crystal detectors. Considerable research and development of silicon materials occurred during the war to develop detectors of consistent quality. Detector and power rectifiers could not amplify a signal. Many efforts were made to develop a solid-state amplifier and were successful in developing a device called the point contact transistor which could amplify 20 dB or more. In 1922, Oleg Losev developed two-terminal, negative resistance amplifiers for radio, but he died in

4620-919: The final issue of the Nascom Newsletter was published. In January 1985, PCW published a letter from Lucas Nascom stating that, while the Nascom 1 had been discontinued, the Nascom 2 and Nascom 3 were still in production. A Nascom advert in January 1980 claimed "over 15,000 systems in operation world-wide". In a retrospective published in May 1989, Marshall claimed that, by May 1980, Nascom had shipped over 35,000 Nascom 1 and Nascom 2 systems, all in kit form. Nascom reported sales of £250,000 in April 1980 The Nascom 1 and Nascom 2 were supplied with full documentation including circuit schematics, construction guide, datasheets for some components and assembly listing for

4704-549: The final keyboard). An article in that issue by K. S. Borland (another director of Nasco Sales Ltd) described the origins and history of the Nascom 1 design. In January 1978, the Lynx Electronics advert in Practical Electronics listed the Nascom 1 in addition to their traditional list of electronic components. By February 1978 and thereafter the whole of their advert was devoted to the Nascom 1. After

4788-400: The keyboard connectors that were unused on the keyboard. On the Nascom 2, this included a connection to the /NMI (non-maskable interrupt) signal. The display of the Nascom 1 and 2 was memory-mapped and consisted of 16 rows of 48 characters. Each row of characters used 64 consecutive memory locations; the extra 16 characters in each line were "hidden" by the video blanking circuitry. Scrolling

4872-543: The material's majority carrier . The opposite carrier is called the minority carrier , which exists due to thermal excitation at a much lower concentration compared to the majority carrier. For example, the pure semiconductor silicon has four valence electrons that bond each silicon atom to its neighbors. In silicon, the most common dopants are group III and group V elements. Group III elements all contain three valence electrons, causing them to function as acceptors when used to dope silicon. When an acceptor atom replaces

4956-565: The memory address map of the Nascom 2 was a superset of the Nascom 1 memory address map; this allowed a high degree of software compatibility between the two machines. The Nascom 1 was implemented entirely using off-the-shelf integrated-circuits and other electronic components . The Nascom 2 used 4, 16-pin bipolar PROMs which acted as glue logic for decode functions ("N2MD" for memory decode, "N2IO" for I/O decode, "N2V" for video decode and N2DB" for data bus buffer control). The Nascom 2 had these additional features that were not present on

5040-512: The memory was ignored). The Nascom 2 used an identical character set but implemented it in a ROM that was footprint compatible with a 2716 2Kbyte device. The Nascom 2 allowed a second 2Kbyte character generator ROM (or EPROM) to be fitted (approximate price £20 in 1980) . The so-called NAS-GRA ROM was used to display characters with the byte codes 0x80–0xFF. The built-in Microsoft BASIC (8K ROM) interpreter could use these graphics to create

5124-435: The mid-19th and first decades of the 20th century. The first practical application of semiconductors in electronics was the 1904 development of the cat's-whisker detector , a primitive semiconductor diode used in early radio receivers. Developments in quantum physics led in turn to the invention of the transistor in 1947 and the integrated circuit in 1958. Semiconductors in their natural state are poor conductors because

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5208-589: The monitor program to enter it in hexadecimal format. The Nascom 1 provided two 24-pin 0.6"-pitch DIL sockets for ROM memory, each wired to accept a 2708 1 KB device. The first monitor program on the Nascom 1 was named NAS-BUG and was supplied as a single 1 KB 2708 EPROM. This was superseded by NAS-BUG T2. All later versions of the monitor were 2 KB in size and so occupied both ROM sockets. The 2 KB monitors were BBUG (a 1 KB extension that co-existed with T2), T4, NAS-SYS 1 and NAS-SYS 3. The Nascom 2 provided one 24-pin 0.6"-pitch DIL socket for ROM memory (other sockets on

5292-505: The movement of charge carriers in a crystal lattice . Doping greatly increases the number of charge carriers within the crystal. When a semiconductor is doped by Group V elements, they will behave like donors creating free electrons , known as " n-type " doping. When a semiconductor is doped by Group III elements, they will behave like acceptors creating free holes, known as " p-type " doping. The semiconductor materials used in electronic devices are doped under precise conditions to control

5376-449: The other. A slice cut from the specimen at the p–n boundary developed a voltage when exposed to light. The first working transistor was a point-contact transistor invented by John Bardeen , Walter Houser Brattain , and William Shockley at Bell Labs in 1947. Shockley had earlier theorized a field-effect amplifier made from germanium and silicon, but he failed to build such a working device, before eventually using germanium to invent

5460-508: The point-contact transistor. In France, during the war, Herbert Mataré had observed amplification between adjacent point contacts on a germanium base. After the war, Mataré's group announced their " Transistron " amplifier only shortly after Bell Labs announced the " transistor ". In 1954, physical chemist Morris Tanenbaum fabricated the first silicon junction transistor at Bell Labs . However, early junction transistors were relatively bulky devices that were difficult to manufacture on

5544-524: The principle behind the light-emitting diode . Oleg Losev observed similar light emission in 1922, but at the time the effect had no practical use. Power rectifiers, using copper oxide and selenium, were developed in the 1920s and became commercially important as an alternative to vacuum tube rectifiers. The first semiconductor devices used galena , including German physicist Ferdinand Braun's crystal detector in 1874 and Indian physicist Jagadish Chandra Bose's radio crystal detector in 1901. In

5628-500: The product with a 16Kbyte DRAM board and NASBUS interconnect but to keep the price at £295 + VAT . This arrangement only required 2 MK4118 devices, allowing Nascom to ship 2,500 systems. By December 1979, PCW reported that the first deliveries of the Nascom 2 were going out. On 23 May 1980, Nascom reported that it had asked Grovewood Securities Ltd to appoint a receiver after it had been unable to secure further investment. Grovewood appointed Messrs Cork Gully, and Marshall resigned from

5712-574: The pure semiconductors, the electrical conductivity may be varied by factors of thousands or millions. A 1 cm specimen of a metal or semiconductor has the order of 10 atoms. In a metal, every atom donates at least one free electron for conduction, thus 1 cm of metal contains on the order of 10 free electrons, whereas a 1 cm sample of pure germanium at 20   °C contains about 4.2 × 10 atoms, but only 2.5 × 10 free electrons and 2.5 × 10 holes. The addition of 0.001% of arsenic (an impurity) donates an extra 10 free electrons in

5796-629: The resistance of specimens of silver sulfide decreases when they are heated. This is contrary to the behavior of metallic substances such as copper. In 1839, Alexandre Edmond Becquerel reported observation of a voltage between a solid and a liquid electrolyte, when struck by light, the photovoltaic effect . In 1873, Willoughby Smith observed that selenium resistors exhibit decreasing resistance when light falls on them. In 1874, Karl Ferdinand Braun observed conduction and rectification in metallic sulfides , although this effect had been discovered earlier by Peter Munck af Rosenschöld ( sv ) writing for

5880-534: The same volume and the electrical conductivity is increased by a factor of 10,000. The materials chosen as suitable dopants depend on the atomic properties of both the dopant and the material to be doped. In general, dopants that produce the desired controlled changes are classified as either electron acceptors or donors . Semiconductors doped with donor impurities are called n-type , while those doped with acceptor impurities are known as p-type . The n and p type designations indicate which charge carrier acts as

5964-472: The same way as the electron. Combined with the negative effective mass of the electrons at the top of the valence band, we arrive at a picture of a positively charged particle that responds to electric and magnetic fields just as a normal positively charged particle would do in a vacuum, again with some positive effective mass. This particle is called a hole, and the collection of holes in the valence band can again be understood in simple classical terms (as with

6048-591: The scale at which the materials are used. A high degree of crystalline perfection is also required, since faults in the crystal structure (such as dislocations , twins , and stacking faults ) interfere with the semiconducting properties of the material. Crystalline faults are a major cause of defective semiconductor devices. The larger the crystal, the more difficult it is to achieve the necessary perfection. Current mass production processes use crystal ingots between 100 and 300 mm (3.9 and 11.8 in) in diameter, grown as cylinders and sliced into wafers . There

6132-425: The semiconductor body by contact with gaseous compounds of the desired element, or ion implantation can be used to accurately position the doped regions. Some materials, when rapidly cooled to a glassy amorphous state, have semiconducting properties. These include B, Si , Ge, Se, and Te, and there are multiple theories to explain them. The history of the understanding of semiconductors begins with experiments on

6216-1007: The semiconductor composition and electrical current allows for the manipulation of the emitted light's properties. These semiconductors are used in the construction of light-emitting diodes and fluorescent quantum dots . Semiconductors with high thermal conductivity can be used for heat dissipation and improving thermal management of electronics. They play a crucial role in electric vehicles , high-brightness LEDs and power modules , among other applications. Semiconductors have large thermoelectric power factors making them useful in thermoelectric generators , as well as high thermoelectric figures of merit making them useful in thermoelectric coolers . A large number of elements and compounds have semiconducting properties, including: The most common semiconducting materials are crystalline solids, but amorphous and liquid semiconductors are also known. These include hydrogenated amorphous silicon and mixtures of arsenic , selenium , and tellurium in

6300-458: The silicon. After the process is completed and the silicon has reached room temperature, the doping process is done and the semiconducting wafer is almost prepared. Semiconductors are defined by their unique electric conductive behavior, somewhere between that of a conductor and an insulator. The differences between these materials can be understood in terms of the quantum states for electrons, each of which may contain zero or one electron (by

6384-559: The success of their seminar in Wembley , Lynx electronics held a similar event in Manchester (Saturday, 1 April 1978. Tickets cost £5.50). The launch price for the Nascom 1 was £197.50 plus 8% VAT , in kit form. The kit included keyboard and sockets for some (but not all) of the ICs . The purchaser needed to supply a TV, a cassette recorder and a power supply. Over its lifetime, the price

6468-407: The term Halbleiter (a semiconductor in modern meaning) in his Ph.D. thesis in 1910. Felix Bloch published a theory of the movement of electrons through atomic lattices in 1928. In 1930, B. Gudden  [ de ] stated that conductivity in semiconductors was due to minor concentrations of impurities. By 1931, the band theory of conduction had been established by Alan Herries Wilson and

6552-406: The use of semiconductors, with the most important aspect being the integrated circuit (IC), which are found in desktops , laptops , scanners, cell-phones , and other electronic devices. Semiconductors for ICs are mass-produced. To create an ideal semiconducting material, chemical purity is paramount. Any small imperfection can have a drastic effect on how the semiconducting material behaves due to

6636-520: The video display required that the CPU and the video circuitry shared access to the video RAM (the CPU had read/write access and the video circuitry had read-only access). If the CPU and the video circuitry accesses the video RAM simultaneously, the CPU was given priority and the video circuitry would read incorrect data. On the Nascom 1 this gave rise to white flicker on the screen that was termed "snow". The International Nascom Microcomputer Club (INMC) published

6720-450: The whole of the I/O address space. On an expanded system, the bus signal /NASIO allowed control of the I/O address space. The memory address map was decoded as follows: 1 or 2 1Kbyte 2708 EPROM 2Kbyte ROM or 2716 EPROM The Nascom keyboards used Licon solid-state (induction transformer) key switches in a matrix arrangement which was scanned under software control. The keys were mounted in

6804-467: The years preceding World War II, infrared detection and communications devices prompted research into lead-sulfide and lead-selenide materials. These devices were used for detecting ships and aircraft, for infrared rangefinders, and for voice communication systems. The point-contact crystal detector became vital for microwave radio systems since available vacuum tube devices could not serve as detectors above about 4000 MHz; advanced radar systems relied on

6888-478: Was implemented under software control. Due to an idiosyncrasy of the video memory decoding on the Nascom 1 (which was then retained on the Nascom 2), the lines were decoded discontiguously, with the top line of the display being the 16th region of memory. The top line was not scrolled, except by the Nascom CP/M implementation. The Nascom 1 used a MCM6576P character generator to display 128 characters (bit 7 of

6972-443: Was reduced to £165 + VAT (March 1979) then £125 + VAT or £140 + VAT assembled (January 1980). By July 1978, The Micronics Company was advertising a cased, built and tested Nascom 1 (with power supply) for £399 + VAT . The advert does not name the machine as a Nascom 1 but the specification is identical. By January 1979, Lynx Electronics had appointed multiple dealers in the UK and were advertising as Nascom Microcomputers, with

7056-637: Was sometimes poor. This was later explained by John Bardeen as due to the extreme "structure sensitive" behavior of semiconductors, whose properties change dramatically based on tiny amounts of impurities. Commercially pure materials of the 1920s containing varying proportions of trace contaminants produced differing experimental results. This spurred the development of improved material refining techniques, culminating in modern semiconductor refineries producing materials with parts-per-trillion purity. Devices using semiconductors were at first constructed based on empirical knowledge before semiconductor theory provided

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