S-Video
S-Video is a signaling standard for standard definition video 480i or 576i. By separating the black-and-white and coloring signals, it achieves better image quality than composite video, but has lower color resolution than component video. Standard analog television signals go through several processing steps on their way to being broadcast, each of which discards information and lowers the quality of the resulting images; the image is captured in RGB form and processed into three signals known as YPbPr. The first of these signals is called Y, created from all three original signals based on a formula that produces an overall brightness of the image, or luma; this signal matches a traditional black and white television signal and the Y/C method of encoding was key to offering backward compatibility. Once the Y signal is produced, it is subtracted from the blue signal to produce Pb and from the red signal to produce Pr. To recover the original RGB information for display, the signals are mixed with the Y to produce the original blue and red, the sum of those is mixed with the Y to recover the green.
A signal with three components is no easier to broadcast than the original three-signal RGB, so additional processing is required. The first step is to combine the Pr to form the C signal, for chrominance; the phase and amplitude of the signal represent the two original signals. This signal is bandwidth-limited to comply with requirements for broadcasting; the resulting Y and C signals are mixed together to produce composite video. To play back composite video, the Y and C signals must be separated, this is difficult to do without adding artifacts; each of these steps is subject to unavoidable loss of quality. To retain that quality in the final image, it is desirable to eliminate as many of the encoding/decoding steps as possible. S-Video is an approach to this problem, it eliminates the final subsequent separation at playback time. The S-video cable carries video using two synchronized signal and ground pairs, termed Y and C. Y is the luma signal, which carries the luminance – or black-and-white – of the picture, including synchronization pulses.
C is the chroma signal. This signal contains the hue of the video; the luminance signal carries horizontal and vertical sync pulses in the same way as a composite video signal. Luma is a signal carrying luminance after gamma correction, is therefore termed "Y" because of the similarity to the lower-case Greek letter gamma. In composite video, the signals co-exist on different frequencies. To achieve this, the luminance signal must be low-pass filtered; as S-Video maintains the two as separate signals, such detrimental low-pass filtering for luminance is unnecessary, although the chrominance signal still has limited bandwidth relative to component video. Compared with component video, which carries the identical luminance signal but separates the color-difference signals into Cb/Pb and Cr/Pr, the color resolution of S-Video is limited by the modulation on a subcarrier frequency of 3.57 to 4.43 megahertz, depending on the standard. This difference is meaningless on home videotape systems, as the chrominance is severely constrained by both VHS and Betamax.
Carrying the color information as one signal means that the color has to be encoded in some way in accord with NTSC, PAL, or SECAM, depending on the applicable local standard. S-Video suffers from low color resolution. NTSC S-Video color resolution is 120 lines horizontal, versus 250 lines horizontal for the Rec. 601-encoded signal of a DVD, or 30 lines horizontal for standard VCRs. In many European Union countries, S-Video was less common because of the dominance of SCART connectors, which are present on most existing televisions, it is possible for a player to output S-Video over SCART, but televisions' SCART connectors are not wired to accept it, if not the display would show only a monochrome image. In this case it is sometimes possible to modify the SCART adapter cable to make it work; some game consoles. Early consoles came with RF adapters, the uncommon composite video on the classic RCA type video jack. Instead of S-Video, consoles like the GameCube had RGB output. In the US and some other NTSC countries, S-Video was provided on some video equipment, including most televisions and game consoles.
The primary exceptions were Beta VCRs. The European usage of RGB video is because the RGB quality of most retro computers and consoles is better than S-Video; the Atari 800 introduced separate Chroma/Luma output in late 1979. The signals were put on pin 5 of a 5-pin 180 degree DIN Connector socket. Atari did not sell a monitor for its 8-bit computer line, however; the Commodore 64 released in 1982 offers separate chroma and luma signals using a different connector. Although Commodore Business Machines did not use the term "S-Video" as the standard did not formally exist until 1987, a simple adapter connects the computer's "LCA" 8-pin DIN socket to a S-Video display, or an S-Video device to the Commodore 1702 monitor's LCA jacks; the four-pin mini-DIN connector is the most common of several S-Video connector types. The same mini-DIN connector is used in the Apple Desktop Bus for Macintosh computers and the two cable types can be interchanged. Other connector variants include seven-pin locking "dub" connectors used on many professional S-VHS machines, dual "Y" and "C" BNC connectors used fo
Commodore 64
The Commodore 64 known as the C64 or the CBM 64, is an 8-bit home computer introduced in January 1982 by Commodore International. It has been listed in the Guinness World Records as the highest-selling single computer model of all time, with independent estimates placing the number sold between 10 and 17 million units. Volume production started in early 1982, marketing in August for US$595. Preceded by the Commodore VIC-20 and Commodore PET, the C64 took its name from its 64 kilobytes of RAM. With support for multicolor sprites and a custom chip for waveform generation, the C64 could create superior visuals and audio compared to systems without such custom hardware; the C64 dominated the low-end computer market for most of the 1980s. For a substantial period, the C64 had between 30% and 40% share of the US market and two million units sold per year, outselling IBM PC compatibles, Apple computers, the Atari 8-bit family of computers. Sam Tramiel, a Atari president and the son of Commodore's founder, said in a 1989 interview, "When I was at Commodore we were building 400,000 C64s a month for a couple of years."
In the UK market, the C64 faced competition from the BBC Micro and the ZX Spectrum, but the C64 was still one of the two most popular computers in the UK. Part of the Commodore 64's success was its sale in regular retail stores instead of only electronics or computer hobbyist specialty stores. Commodore produced many of its parts in-house to control costs, including custom integrated circuit chips from MOS Technology, it has been compared to the Ford Model T automobile for its role in bringing a new technology to middle-class households via creative and affordable mass-production. 10,000 commercial software titles have been made for the Commodore 64 including development tools, office productivity applications, video games. C64 emulators allow anyone with a modern computer, or a compatible video game console, to run these programs today; the C64 is credited with popularizing the computer demoscene and is still used today by some computer hobbyists. In 2011, 17 years after it was taken off the market, research showed that brand recognition for the model was still at 87%.
In January 1981, MOS Technology, Inc. Commodore's integrated circuit design subsidiary, initiated a project to design the graphic and audio chips for a next generation video game console. Design work for the chips, named MOS Technology VIC-II and MOS Technology SID, was completed in November 1981. Commodore began a game console project that would use the new chips—called the Ultimax or the Commodore MAX Machine, engineered by Yash Terakura from Commodore Japan; this project was cancelled after just a few machines were manufactured for the Japanese market. At the same time, Robert "Bob" Russell and Robert "Bob" Yannes were critical of the current product line-up at Commodore, a continuation of the Commodore PET line aimed at business users. With the support of Al Charpentier and Charles Winterble, they proposed to Commodore CEO Jack Tramiel a true low-cost sequel to the VIC-20. Tramiel dictated. Although 64-Kbit dynamic random-access memory chips cost over US$100 at the time, he knew that DRAM prices were falling, would drop to an acceptable level before full production was reached.
The team was able to design the computer because, unlike most other home-computer companies, Commodore had its own semiconductor fab to produce test chips. The chips were complete by November, by which time Charpentier and Tramiel had decided to proceed with the new computer; the product was code named the VIC-40 as the successor to the popular VIC-20. The team that constructed it consisted of Yash Terakura, Shiraz Shivji, Bob Russell, Bob Yannes and David A. Ziembicki; the design and some sample software were finished in time for the show, after the team had worked tirelessly over both Thanksgiving and Christmas weekends. The machine used the same case, same-sized motherboard, same Commodore BASIC 2.0 in ROM as the VIC-20. BASIC served as the user interface shell and was available on startup at the READY prompt; when the product was to be presented, the VIC-40 product was renamed C64. The C64 made an impressive debut at the January 1982 Consumer Electronics Show, as recalled by Production Engineer David A. Ziembicki: "All we saw at our booth were Atari people with their mouths dropping open, saying,'How can you do that for $595?'"
The answer was vertical integration. Commodore had a reputation for announcing products that never appeared, so sought to ship the C64. Production began in spring 1982 and volume shipments began in August; the C64 faced a wide range of competing home computers, but with a lower price and more flexible hardware, it outsold many of its competitors. In the United States the greatest competitors were the Atari 8-bit 400, the Atari 800, the Apple II; the Atari 400 and 800 had been designed to accommodate stringent FCC emissions requirements and so were expensive to
North America
North America is a continent within the Northern Hemisphere and all within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16.5% of the earth's land area and about 4.8% of its total surface. North America is the third largest continent by area, following Asia and Africa, the fourth by population after Asia and Europe. In 2013, its population was estimated at nearly 579 million people in 23 independent states, or about 7.5% of the world's population, if nearby islands are included. North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge 40,000 to 17,000 years ago; the so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago. The Classic stage spans the 6th to 13th centuries.
The Pre-Columbian era ended in 1492, the transatlantic migrations—the arrival of European settlers during the Age of Discovery and the Early Modern period. Present-day cultural and ethnic patterns reflect interactions between European colonists, indigenous peoples, African slaves and their descendants. Owing to the European colonization of the Americas, most North Americans speak English, Spanish or French, their culture reflects Western traditions; the Americas are accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass unknown by Europeans. In 1507, Waldseemüller produced a world map, in which he placed the word "America" on the continent of South America, in the middle of what is today Brazil, he explained the rationale for the name in the accompanying book Cosmographiae Introductio:... ab Americo inventore... quasi Americi terram sive Americam.
For Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespucci's name, but in its feminine form "America", following the examples of "Europa", "Asia" and "Africa". Other mapmakers extended the name America to the northern continent, In 1538, Gerard Mercator used America on his map of the world for all the Western Hemisphere; some argue that because the convention is to use the surname for naming discoveries, the derivation from "Amerigo Vespucci" could be put in question. In 1874, Thomas Belt proposed a derivation from the Amerrique mountains of Central America. Marcou corresponded with Augustus Le Plongeon, who wrote: "The name AMERICA or AMERRIQUE in the Mayan language means, a country of perpetually strong wind, or the Land of the Wind, and... the can mean... a spirit that breathes, life itself." The United Nations formally recognizes "North America" as comprising three areas: Northern America, Central America, The Caribbean.
This has been formally defined by the UN Statistics Division. The term North America maintains various definitions in accordance with context. In Canadian English, North America refers to the land mass as a whole consisting of Mexico, the United States, Canada, although it is ambiguous which other countries are included, is defined by context. In the United States of America, usage of the term may refer only to Canada and the US, sometimes includes Greenland and Mexico, as well as offshore islands. In France, Portugal, Romania and the countries of Latin America, the cognates of North America designate a subcontinent of the Americas comprising Canada, the United States, Mexico, Greenland, Saint Pierre et Miquelon, Bermuda. North America has been referred to by other names. Spanish North America was referred to as Northern America, this was the first official name given to Mexico. Geographically the North American continent has many subregions; these include cultural and geographic regions. Economic regions included those formed by trade blocs, such as the North American Trade Agreement bloc and Central American Trade Agreement.
Linguistically and culturally, the continent could be divided into Latin America. Anglo-America includes most of Northern America and Caribbean islands with English-speaking populations; the southern North American continent is composed of two regions. These are the Caribbean; the north of the continent maintains recognized regions as well. In contrast to the common definition of "North America", which encompasses the whole continent, the term "North America" is sometimes used to refer only to Mexico, the United States, Greenland; the term Northern America refers to the northern-most countries and territories of North America: the United States, Bermuda, St. Pierre and Miquelon and Greenland. Although the term does not refer to a unifie
DVD player
A DVD player is a device that plays DVD discs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. Some DVD players will play audio CDs. DVD players are connected to a television to watch the DVD content, which could be a movie, a recorded TV show, or other content; the first DVD player was created by Sony Corporation in Japan in collaboration with Pacific Digital Company from the United States in 1997. Some manufacturers announced that DVD players would be available as early as the middle of 1996; these predictions were too optimistic. Delivery was held up for "political" reasons of copy protection demanded by movie studios, but was delayed by lack of movie titles; the first players appeared in Japan on November 1, 1996, followed by the United States on March 26, 1997 with distribution limited to only seven major cities for the first six months. Players trickled into other regions around the world. Prices for the first players in 1997 started at $600 and could top out at prices over $1000.
By the end of 2000, players were available for under $100 at discount retailers. In 2003 players became available for under $50. Six years after the initial launch, close to one thousand models of DVD players were available from over a hundred consumer electronics manufacturers. Fujitsu released the first DVD-ROM-equipped computer on November 6th in GB. Toshiba released a DVD-ROM-equipped computer and a DVD-ROM drive in Japan in early 1997. DVD-ROM drives from Toshiba, Panasonic and Sony began appearing in sample quantities as early as January 1997, but none were available before May; the first PC upgrade kits became available from Creative Labs, Hi-Val, Diamond Multimedia in April and May 1997. In 2014, every major PC manufacturer has models that include DVD-ROM drives; the first DVD-Audio players were released in Japan by Pioneer in late 1999, but they did not play copy-protected discs. Matsushita first released full-fledged players in July 2000 for $700 to $1,200. DVD-Audio players are now made by Aiwa, Denon, JVC, Madrigal, Nakamichi, Toshiba and others.
Sony released the first SACD players in May 1999 for $5,000. Pioneer's first DVD-Audio players released in late 1999 played SACD. SACD players are now made by Accuphase, Denon, Marantz, Philips and others. A DVD player has to complete these tasks: Read a DVD disc in ISO – UDF version 1.02 format Optionally decrypt the data with either CSS and/or Macrovision Read and obey the DVD's Regional lockout codes and display a warning if the player is not authorized to play the DVD Decode the MPEG-2 video stream with a maximum of 10 Mbit/s or 8 Mbit/s Decode sound in MP2, PCM or AC-3 format and output on stereo connector, optical or electric digital connector Output a video signal, either an analog one on the composite, S-Video, SCART, or component video connectors, or a digital one on the DVI or HDMI connectors. DVD players cannot play Blu-ray discs due to using different wavelength laser's Blu ray use a Blue Violet laser instead of a Red laser. However, all Blu-ray players are "backwards compatible" and they will play DVD's and some are compatible with CD and other disc formats.
Additionally, most DVD players allow users to play audio CDs and Video CDs. A few include a home cinema decoder; some newer devices play videos in the MPEG-4 ASP video compression format popular in the Internet. Most hardware DVD players must be connected to a television. Portable DVD players are used for long road trips and travel, they have a plug for the 12 volt power jack in cars. Some models have two screens, so that two people in the back seat can both watch the movie. Other portable DVD players have a single screen that opens up like a laptop computer screen. Due to multiple audio output devices, there are many outputs on a DVD player, such as an RCA jack, component outputs, an HDMI output. Consumers may become confused with how to connect a player to a TV or amplifier. Most systems include an optional digital audio connector for this task, paired with a similar input on the amplifier; the physical connection is RCA connectors or TOSLINK, which transmits a S/PDIF stream carrying either uncompressed digital audio or the original compressed audio data to be decoded by the audio equipment.
Video is another issue which continues to present most problems. Current players output analog video only, both composite video on an RCA jack as well as S-Video in the standard connector. However, neither connector was intended to be used for progressive video, so yet another set of connectors has started to appear, to carry a form of component video, which keeps the three components of the video, one luminance signal and two color difference signal, as stored on the DVD itself, on separate wires; the connectors are further confused by using a number of different physical connectors on different player models, RCA or BNC, as well as using VGA cables in a non-standard way. Worse, there are two sets of component outputs, one carrying interlaced v
Video game console
A video game console is a computer device that outputs a video signal or visual image to display a video game that one or more people can play. The term "video game console" is used to distinguish a console machine designed for consumers to use for playing video games, in contrast to arcade machines or home computers. An arcade machine consists of a video game computer, game controller and speakers housed in large chassis. A home computer is a personal computer designed for home use for a variety of purposes, such as bookkeeping, accessing the Internet and playing video games. While arcades and computers are expensive or “technical” devices, video game consoles were designed with affordability and accessibility to the general public in mind. Unlike similar consumer electronics such as music players and movie players, which use industry-wide standard formats, video game consoles use proprietary formats which compete with each other for market share. There are various types of video game consoles, including home video game consoles, handheld game consoles and dedicated consoles.
Although Ralph Baer had built working game consoles by 1966, it was nearly a decade before the Pong game made them commonplace in regular people's living rooms. Through evolution over the 1990s and 2000s, game consoles have expanded to offer additional functions such as CD players, DVD players, Blu-ray disc players, web browsers, set-top boxes and more; the first video games appeared in the 1960s. They were played on massive computers connected to vector displays, not analog televisions. Ralph H. Baer conceived the idea of a home video game in 1951. In the late 1960s, while working for Sanders Associates, Baer created a series of video game console designs. One of these designs, which gained the nickname of the 1966 "Brown Box", featured changeable game modes and was demonstrated to several TV manufacturers leading to an agreement between Sanders Associates and Magnavox. In 1972, Magnavox released the Magnavox Odyssey, the first home video game console which could be connected to a TV set. Ralph Baer's initial design had called for a huge row of switches that would allow players to turn on and off certain components of the console to create different games like tennis, volleyball and chase.
Magnavox replaced the switch design with separate cartridges for each game. Although Baer had sketched up ideas for cartridges that could include new components for new games, the carts released by Magnavox all served the same function as the switches and allowed players to choose from the Odyssey's built-in games; the Odyssey sold about 100,000 units, making it moderately successful, it was not until Atari's arcade game Pong popularized video games that the public began to take more notice of the emerging industry. By autumn 1975, bowing to the popularity of Pong, canceled the Odyssey and released a scaled-down version that played only Pong and hockey, the Odyssey 100. A second, "higher end" console, the Odyssey 200, was released with the 100 and added on-screen scoring, up to four players, a third game—Smash. Released with Atari's own home Pong console through Sears, these consoles jump-started the consumer market. All three of the new consoles used simpler designs than the original Odyssey did with no board game pieces or extra cartridges.
In the years that followed, the market saw many companies rushing similar consoles to market. After General Instrument released their inexpensive microchips, each containing a complete console on a single chip, many small developers began releasing consoles that looked different externally, but internally were playing the same games. Most of the consoles from this era were dedicated consoles playing only the games that came with the console; these video game consoles were just called video games because there was little reason to distinguish the two yet. While a few companies like Atari and newcomer Coleco pushed the envelope, the market became flooded with simple, similar video games. Fairchild released the Fairchild Video Entertainment System in 1976. While there had been previous game consoles that used cartridges, either the cartridges had no information and served the same function as flipping switches or the console itself was empty and the cartridge contained all of the game components.
The VES, contained a programmable microprocessor so its cartridges only needed a single ROM chip to store microprocessor instructions. RCA and Atari soon released their own cartridge-based consoles, the RCA Studio II and the Atari 2600, respectively; the first handheld game console with interchangeable cartridges was the Microvision designed by Smith Engineering, distributed and sold by Milton-Bradley in 1979. Crippled by a small, fragile LCD display and a narrow selection of games, it was discontinued two years later; the Epoch Game Pocket Computer was released in Japan in 1984. The Game Pocket Computer featured an LCD screen with 75 X 64 resolution and could produce graphics at about the same level as early Atari 2600 games; the system sold poorly, as a result, only five games were made for it. Nintendo's Game & Watch series of dedicated game systems proved more successful, it helped to establish handheld gaming as popular and lasted until 1991. Many Game & Watch games were re-released on Nintendo's subsequent handheld systems.
The VES continued to be sold at a profit after 1977, both Bally and Magnavox brought their own programmable cartridge-based consoles to the market. However, i
Atari 2600
The Atari 2600 sold as the Atari Video Computer System or Atari VCS until November 1982, is a home video game console from Atari, Inc. Released on September 11, 1977, it is credited with popularizing the use of microprocessor-based hardware and games contained on ROM cartridges, a format first used with the Fairchild Channel F in 1976; this contrasts with the older model of having dedicated hardware that could play only those games that were physically built into the unit. The 2600 was bundled with two joystick controllers, a conjoined pair of paddle controllers, a game cartridge: Combat, Pac-Man; the Atari VCS launched with nine low-resolution games in 2 KiB cartridges. Disagreements over sales potential of the VCS led Bushnell to leave Atari in 1978; the system found its killer app with the port of Taito's Space Invaders in 1980 and became successful, leading to the creation of third-party game developers, notably Activision, competition from other home console makers such as Mattel and Coleco.
By the end of its primary lifecycle in 1983-4, the 2600 was home to games with much more advanced visuals and gameplay than the system was designed for, such as scrolling platform adventure Pitfall II: Lost Caverns, which uses four times the ROM of the launch titles. Atari invested in two games for the 2600, Pac-Man and E. T. the Extra-Terrestrial, that would become commercial failures and contributed to the video game crash of 1983. The 2600 was shelved as the industry recovered, while Warner sold off the home console division of Atari to Commodore CEO Jack Tramiel; the new Atari Corporation under Tramiel re-released a lower-cost version of the 2600 in 1986, as well as the Atari 7800, backwards compatible with the 2600. Atari dropped support for the Atari 2600 on January 1, 1992, after an estimated 30 million units were sold over the system's lifetime. Atari was founded by Nolan Bushnell and Ted Dabney of which their first major product was Pong in 1972, one of the first successful arcade games.
It transitioned Pong into a home console version by 1975, helping to pit Atari against Magnavox, the only other major competitor for home consoles at the time. Bushnell recognized that this approach to home consoles has a drawback in that because it used custom logic burned onto the circuit board, it was limited to only one game and any variants, would require consumers to buy another console to play a different set of games. Further, while they could continue to take games they had created for arcade machines to home consoles, this development step cost at least US$100,000 and time to complete, once on the market, had only about a three-month shelf life before being outdated, making this a risky move. In 1974, Atari had acquired Cyan Engineering, an electronics company founded by Steve Mayer and Larry Emmons, both former colleagues of Bushnell and Dabney from Ampex, started Atari's Grass Valley Think Tank, where they were involved with coming up with new ideas for arcade games. Based on Bushnell's concern about single-game consoles, the Grass Valley team started working on how to achieve a home console with multi-game support.
Mayer and Emmons recognized that to achieve a home console with multiple game functionality, they would need newly-invented microprocessors within the console, but at that time, such microprocessors cost US$100–300, far outside the range that their market would support. In September 1975, Chuck Peddle of MOS Technology had created a low-cost replacement for the Motorola 6800, the MOS Technology 6502, which they introduced at the 1975 Wescon trade show in San Francisco. Mayer and Ron Milner attended the show, met with Peddle, invited Peddle to Cyan's headquarters to discuss using MOS's microprocessors for a game console. Mayer and Milner had been able to negotiate purchase of the 6502 chips for US$8 a piece, sufficient to begin development of a console. Through their discussions, Cyan and MOS decided that the better solution would be the MOS Technology 6507, a more restrictive but lower-cost version of the 6502. Cyan and MOS arranged to bring in Synertek, a semiconductor manufacturer whose co-founder, Bob Schreiner, was good friends with Peddle, to act as a second source for the 6507.
By December 1975, Atari hired Joe Decuir to help design the first prototype around the 6502, codenamed "Stella", the name of Decuir's bicycle. A second prototype had been completed by March 1976 with the help of Jay Miner, able to squeeze an entire wire wrap of equipment making up the Television Interface Adaptor, sending graphics and audio to the television display, into a single chip; the second prototype included the 6507, the TIA, a ROM cartridge slot and adapter, each cartridge holding a ROM image of a game. Believing that "Stella" would be a success, Bushnell acquired the entire Grass Valley Think Tank and relocated them into Atari's new headquarters in Sunnyvale, California by mid-1976, putting Steve Mayer in charge of the project. Bushnell feared that once this unit was released, competitors would try to copy it, preemptively made arrangements with all integrated chip manufacturers that had interest in the games market to deny sales to his competitors. Fairchild Semiconductor introduced its Fairchild Channel F home console in November 1976, which included ROM cartridge technology, beating Atari to the market.
The company lacked the funds to do so. Bushnell had considered taking Atari public but instead decided to sell the company to Warner Communications for US$28 million, subsequently Warner provided around US$100 million to Atari, allowing them to prioritize and fast-track Stella. By 1977, the product had advanced far enough to brand it as the "Atari Video Computer System" and enga
Tangerine Microtan 65
The Tangerine Microtan 65 was a 6502 based single board microcomputer, first sold in 1979, which could be expanded into, what was for its day, a comprehensive and powerful system. The design became the basis for what became the ORIC ATMOS and computers, which had similar keyboard addressing and tape I/O as in the Microtan 65; the Microtan 65 had a single step function. The computer was available as ready-built boards or as kits consisting of board and components requiring soldering together; the Microtan 65 was intended as a general purpose microcomputer which could be used by laboratories, Original Equipment Manufacturers s and the computer enthusiast, it was designed with expandability in mind. In this way the customer could customise the system, be it as a specialised control system, as a learning tool, or as a general purpose computing device. Price of the Microtan 65 board in 1981 was £ 79.35 in £ 90.85 ready-assembled. The system was not available in the shops, one of the few stockists at the time being Henry's Radio of Edgware Road, London.
To accompany the hardware and to offer further support to users, a magazine was created, the Tansoft Gazette. This was edited by Tangerine employee Paul Kaufman who continued as editor when the magazine was renamed Oric Owner. Tansoft became the name of Tangerine Computer's official software house which supplied a number of software products and book for the Microtan system and subsequently for the Oric range of computers; the Tansoft Gazette was prepared in-house using basic layout facilities and printed by local printer, Mid-Anglia Litho. Oric Owner improved on this by using a professional typsetting company; the Microtan 65 was quite simple by today's standards, with: an NMOS 6502 CPU running at 750 kHz clock rate 1K byte of RAM, used both for display memory and user programs 1K byte of ROM for the monitor program) video logic and a television RF modulator, for the 16 rows of 32 characters display a software scanned hexadecimal keypad an optional ASCII keyboard The major advance that the Microtan 65 had over a lot of the competition at that time was that the video display was flicker free.
At the time a lot of microcomputers would either access the screen memory asynchronously to the video timing, or would write to the screen memory during a non-display period. The Microtan 65 got over this problem by making use of an incidental feature of the 6502; the 6502 has a regular period in each instruction cycle when all CPU activity is inside the chip, leaving the external memory available without using complex external arbitration logic. This meant that video accesses could be made at maximum speed; this technique is used on the Oric-1 and Atmos, in the unrelated Apple II. The 32 × 16 characters was the reason. To get the circuitry to work at a standard video rate meant that the pixel clock had to be 6 MHz; when the Microtan 65 was designed only a 1 MHz 6502 was available, so 750 kHz was used. The 1K byte monitor program was called TANBUG; the software facilities were rudimentary: M = Memory modify / examine L = List a block of memory G = Go command R = Registers display / modify S = set Single step mode N = set Normal mode P = Proceed command B = set Breakpoints O = calculate Offset for use in branch instructions C = Copy a block of memory The Microtan 65 memory map is shown below: $0000 Zero Page $0100 Stack $0200 Screen RAM $0300 $0400 End of Microtan 65 RAM - map continued from $0400 to $0700 as RAM on TANEX $8000 I/O $C000 $F800 TANBUG V2 $FFFFThe screen memory occupies the space between $200 and $3FF.
In addition to the standard 8 bits of screen RAM, there was an additional single bit RAM shadowing the $200 to $300 space. This was configured as a 9th bit write-only plane, was used by the Microtan 65 for rudimentary, or "chunky", graphics. Setting the 9th bit displayed a Minitel type block graphic; the display is 32 characters across by 16 lines down, with memory address $200 representing the top left hand displayed character, $220 the second row, etc. The character representation is standard ASCII. Several pieces of Microtan 65 software write to the bottom line by writing to memory starting at $3E0 - the leftmost character on the bottom line, rather than vectoring through TANBUG. I/O in the Microtan 65 is decoded into a 16 KB space to simplify the hardware. In fact the 1 KB of RAM is mirrored through the bottom 32 KB, the I/O through the next 16 KB, the EPROM through the top 16 KB. If you added an expansion board the decoding was modified and the wasted space reclaimed. In common with other 6502 designs, I/O is mapped into the memory space.
There is no dedicated I/O space as on 8086 etc.. The I/O ports are: Write to $BFF0 Clear Keyboard Flag Read from $BFF0 Turn Graphics On Write to $BFF1 Used by the hardware single step Write to $BFF2 To write a scan pattern to the hex keypad Write to $BFF3 Turn off Graphics Read From $BFF3 Read Keyboard Port. Adding a TANEX board provided a number of features: an add-on to TANBUG called XBUG space for an additional 7K bytes of RAM five EPROM sockets two 6522 VIAs a 6551 UART, providing a cassette interface for storing and
