Atari 8-bit family

Atari 400 (1979) with a membrane keyboard and a door covering the single cartridge slot.

Atari 800 with the cover removed, showing expansion cards and two cartridge slots. The slots are molded into the cast aluminum RF shield.

The Atari 800 uses expansion cards for the RAM, ROM, and processor. It eventually shipped with three of these 16KB RAM cards, for a total of 48KB.

Management identified two sweet spots for the new computers: a low-end version known internally as "Candy", and a higher-end machine known as "Colleen" (named after two Atari secretaries).[15] Atari would market Colleen as a computer and Candy as a game machine or hybrid game console. Colleen included user-accessible expansion slots for RAM and ROM, two 8 KB ROM cartridge slots, RF and monitor output (including two pins for separate luma and chroma, allowing a complete S-Video output) and a full keyboard. Candy was initially designed as a game console, lacking a keyboard and input/output ports, although an external keyboard was planned that could be plugged into joystick ports 3 and 4. At the time, plans called for both to have a separate audio port supporting cassette tapes as a storage medium.[16]

A goal for the new systems was user-friendliness. One executive stated, "Does the end user care about the architecture of the machine? The answer is no. 'What will it do for me?' That's his major concern. ... why try to scare the consumer off by making it so he or she has to have a double E or be a computer programmer to utilize the full capabilities of a personal computer?" Cartridges would for example, Atari believed, make the computers easier to use.[17] To minimize handling of bare circuit boards or chips, as was common with other systems of that period, the computers were designed with enclosed modules for memory, ROM cartridges, with keyed connectors to prevent them being plugged into the wrong slot. The operating system boots automatically, loading drivers from devices on the serial bus (SIO). The DOS system for managing floppy storage was menu-driven. When no software is loaded, rather than leaving the user at a blank screen or machine language monitor, the OS goes to the "Memo Pad" mode allowing the user to type using the built-in full-screen editor.[13]

As the design process for the new machines continued, there were questions about what the Candy should be. There was a running argument about whether the keyboard would be external or built in.[18] By the summer of 1978, education had become a focus for the new systems. While the Colleen design was largely complete by May 1978, it was not until early 1979 that the decision was made that Candy would also be a complete computer, but one intended for children. As such, it would feature a new keyboard designed to be resistant to liquid spills.[19]

Atari intended to port Microsoft BASIC to the machine as an 8 KB ROM cartridge. However, the existing 6502 version from Microsoft was around 7,900 bytes, leaving no room for extensions for graphics and sound. The company contracted with local consulting firm Shepardson Microsystems to complete the port. They recommended writing a new version from scratch, resulting in Atari BASIC.[20]

At the time the 400 and 800 were being designed, the Federal Communications Commission (FCC) mandated consumer devices to have extremely low signal leakage in the television frequency range. An RF modulator is normally used for television output, which is difficult to shield to the mandated levels. Other manufacturers avoided this by using built-in composite monitors, such as the Commodore PET and TRS-80.[lower-alpha 3]

In a July 1977 visit with the engineering staff, a Texas Instruments (TI) salesman presented a new possibility in the form of an inexpensive fibre optic cable with built-in transceivers. During the meeting, Joe Decuir proposed placing an RF modulator on one end, thereby completely isolating any electrical signals so that the computer itself would have no RF components. His manager, Wade Tuma, later shot down the idea saying "The FCC would never let us get away with that stunt." Unknown to Atari, TI was designing its own computer, the TI-99/4, and decided to use Decuir's idea. As Tuma had predicted, the FCC rejected the design and this led to delays in that machine's release.[21]

To meet the off-the-shelf requirement while including internal TV circuitry, the machines needed to be heavily shielded. Both were built around very strong cast aluminum shields forming a partial Faraday cage, with the various components screwed down onto this internal framework. This resulted in an extremely sturdy computer, at the disadvantage of added manufacturing expense and complexity.[3]

The FCC ruling also made it difficult to have any sizable holes in the case, which eliminated expansion slots or cards that communicated with the outside world via their own connectors. Instead, Atari designed the Serial Input/Output (SIO) computer bus, a daisy-chainable system that allowed multiple, auto-configuring devices to connect to the computer through a single shielded connector. The internal slots were reserved for ROM and RAM modules; they did not have the control lines necessary for a fully functional expansion card, nor room to route a cable outside the case to communicate with external devices.[3]

After announcing intent to enter the home computer market in December 1978,[22] the Atari 400 and Atari 800 were presented at the Winter CES in January 1979[23] and shipped in November of the same year.

The names originally referred to the amount of memory: 4 KB RAM in the 400 and 8 KB in the 800. By the time they were released, RAM prices had started to fall, so the machines were both released with 8 KB, using 4kx1 DRAMs. The user-installable RAM modules in the 800 initially had plastic casings but this proved to have overheating issues, so the casings were removed. Later, the expansion cover was held down with screws instead of the easier to open plastic latches.[24] The computers eventually shipped with maxed-out RAM: 16k and 48k respectively, using 16kx1 DRAMs.

Both models have four joystick ports, but only a few games such as M.U.L.E. use them all to permit four simultaneous players. Paddle controllers are wired in pairs, and eight players can play Super Breakout.[25] The Atari 400, despite its membrane keyboard and single internal ROM slot, outsold the Atari 800 by a 2-to-1 margin.[4] Only one cartridge for the 800's right slot was produced by March 1983, and later machines in the family omitted the slot.[26][25]

Creative Computing mentioned the Atari machines in an April 1979 overview of the CES show. Calling Atari "the videogame people", it went on to state they came with "some fantastic educational, entertainment and home applications software".[27] In an August 1979 interview Atari's Peter Rosenthal suggested that demand might be low until the 1980-81 time frame, when he predicted about one million home computers being sold.[28] The April 1980 issue compared the machines with the Commodore PET, focused mostly on the BASIC dialects.[29]

Ted Nelson reviewed the computer in the magazine in June 1980, calling it "an extraordinary graphics box". Describing his and a friend's "shouting and cheering and clapping" during a demo of Star Raiders, Nelson wrote that he was so impressed that "I've been in computer graphics for twenty years, and I lay awake night after night trying to understand how the Atari machine did what it did". He described the machine as "something else" before criticizing the company for a lack of developer documentation. Nelson concluded by stating "The Atari is like the human body - a terrific machine, but (a) they won't give you access to the documentation, and (b) I'd sure like to meet the guy that designed it".[30]

Kilobaud Microcomputing wrote in September 1980 that the Atari 800 "looks deceptively like a video game machine, [but had] the strongest and tightest chassis I have seen since Raquel Welch. It weighs about ten pounds ... The large amount of engineering and design in the physical part of the system is evident". The reviewer also praised the documentation as "show[ing] the way manuals should be done", and the "excellent 'feel'" of the keyboard.[31]

InfoWorld favorably reviewed the 800's performance, graphics, and ROM cartridges, but disliked the documentation and cautioned that the unusual right Shift key location might make the computer "unsuitable for serious word processing".[lower-alpha 4] Noting that the amount of software and hardware available for the computer "is no match for that of the Apple II or the TRS-80", the magazine concluded that the 800 "is an impressive machine that has not yet reached its full computing potential".[32]

Despite planning an extensive advertising campaign for 1980,[17] Atari found competing with microcomputers from market leaders Commodore, Apple, and Tandy difficult. By mid-1981 it had reportedly lost $10 million on sales of $10–13 million from more than 50,000 computers.[33][34]

In 1982, Atari started the Sweet 8 (or "Liz NY") and Sweet 16 projects to create an upgraded set of machines that were easier to build and less costly to produce. Atari ordered a custom 6502, initially labelled 6502C, but eventually known as SALLY to differentiate it from a standard 6502C.[lower-alpha 5] SALLY was incorporated into late-production 400/800 machines, all XL/XE models, and the Atari 5200 and 7800 consoles. SALLY adds logic to disable the clock signal, called HALT. This lets ANTIC shut off the CPU to access the data/address bus, allowing them to coexist.[35]

Like the earlier machines, the Sweet 8/16 was intended to be released in two versions: the 1000 with 16 KB, and the 1000X with 64 KB. To support expansion, similar to the card slots used in the Apple II, the 1000 series also supported the Parallel Bus Interface (PBI), a single expansion slot on the back of the machine. An external chassis could be plugged into the PBI, supporting card slots for further expansion.

Atari 1200XL

The original Liz plans were dropped and only one machine using the new design was released. Announced at a New York City press conference on December 13, 1982,[36][37] the rechristened 1200XL was presented at the Winter CES on January 6–9, 1983.[38] It shipped in March 1983[39] with 64 KB of RAM, built-in self test, a redesigned keyboard (with four function keys and a HELP key), and redesigned cable port layout.[26]

Announced with a $1000 price,[40] the 1200XL was released at $899.[38] This was $100 less than the announced price of the 800 at its release in 1979,[1] but by this time the 800 was available for much less.

The 1200XL omitted several features, or they were poorly implemented. The PBI expansion connector from the original 1000X design was omitted, making the design rely entirely on the SIO port again. The +12V pin in the SIO port was left unconnected; only +5V power was available which made a few devices stop working.[lower-alpha 6] An improved video circuit provided more chroma for a more colorful image, but the chroma line was not connected to the monitor port, the only place that could make use of it. The rearrangement of the ports made some joysticks and cartridges difficult or impossible to use. Changes made to the operating system resulted in compatibility problems with some older software.

It was discontinued in June 1983. There was no PAL version of the 1200XL.

The press warned that the 1200XL was too expensive. Compute! stated in an early 1983 editorial:[41]

We're hard pressed to figure out what Atari is up to ... We're concerned about the emperor's new clothes because the actual features of the XL seem off base when compared to the competition. For example, the Atari 800, [less than $700] ... we're concerned that the 1200XL has been introduced to fill a nonexistent hole in Atari's product line.

John J. Anderson, writing in Creative Computing's Outpost: Atari column, echoed these comments:[42]

If it had been announced at $499 instead of $899, it would have been a welcome addition to the Atari computer line... The 1200 has met with nearly universal insouciance in the microcomputer community, and for good reason. It has an extra 16K in a designer case, without a right cartridge slot, expansion slots, or a third and fourth controller jack. It has no standard parallel or RS-232 ports. Only substantive price cuts will help its image in any tangible way.

Bill Wilkinson, author of Atari BASIC, co-founder of Optimized Systems Software, and columnist for Compute!, in May 1983 criticized the computer's features and price:[43]

So how do I rate the 1200XL in overall features and performance? Quite honestly, it depends entirely on what the price of the machine is. At anything under $450, it's a terrific bargain ... it should be able to sell for half the cost of the 800. However, the indications are that the price of the 800 will be dropped and that the 1200 will cost more than the 800. If so, buy an 800 quick!

The 800XL was the best-selling model in the Atari 8-bit line.

The 600XL has a slightly shallower case than the 800XL, as it lacks one row of RAM chips.

By this point in time Atari was involved in what would soon develop into a full-blown price war. Several years earlier, Commodore was a major calculator vendor, selling designs based on a Texas Instruments (TI) chipset. TI decided to enter the market themselves and suddenly raised the prices to other vendors, nearly putting Commodore out of business.

To ensure his supply of the 6502, Jack Tramiel of Commodore International purchased MOS Technology. When TI introduced the TI-99, Tramiel turned the tables on them by pricing his machines below theirs. A price war ensued, causing a dramatic decline in home computer prices, reducing them as much as eight times over a period of a few months.

In May 1981, the Atari 800's price was $1,050,[32] but by mid-1983 it was $165[44] and the 400 was under $150.[40] Although Atari had never been a deliberate target of Tramiel's wrath, the Commodore/TI price war affected the entire market. The timing was particularly bad for Atari; the 1200XL was a flop, and the earlier machines were too expensive to produce to be able to compete at the rapidly falling price points.

A new lineup was announced at the 1983 Summer CES, closely following the original Liz/Sweet concepts. The 600XL was essentially the Liz NY model, and the spiritual replacement for the 400, while the 800XL would replace both the 800 and 1200XL. The machines looked similar to the 1200XL, but were smaller back to front, the 600 being somewhat smaller as it lacked one row of memory chips on the circuit board. The high-end 1400XL added a built-in 300 baud modem and a voice synthesizer, and the 1450XLD also included a built-in double-sided floppy disk drive in an enlarged case, with a slot for a second drive. The machines had Atari BASIC built into the ROM of the computer and the PBI at the back that allowed external expansion.

The 800XL main circuit board

Atari had difficulty in transitioning manufacturing to Asia after closing its US factory.[45] Originally intended to replace the 1200XL in mid-1983, the new models did not arrive until late that year. Although the 600XL/800XL were well positioned in terms of price and features, during the critical Christmas season they were available only in small numbers while the Commodore 64 was widely available.[46] Brian Moriarty stated in ANALOG Computing that Atari "fail[ed] to keep up with Christmas orders for the 600 and 800XLs", reporting that as of late November 1983 the 800XL had not appeared in Massachusetts stores while 600XL "quantities are so limited that it's almost impossible to obtain".[47]

Although the 800XL would ultimately be the most popular computer sold by Atari, the company was unable to defend its market share, and the ongoing race to the bottom reduced Atari's profits. Prices continued to erode; by November 1983 one toy store chain sold the 800XL for $149.97, $10 above the wholesale price. After losing $563 million in the first nine months of the year, Atari that month announced that prices would rise in January, stating that it "has no intention of participating in these suicidal price wars".[48] The 600XL and 800XL's prices in early 1984 were $50 higher than for the Commodore VIC-20 and 64,[49] and a rumor stated that the company planned to discontinue hardware and only sell software.[50] Combined with the simultaneous effects of the video game crash of 1983, Atari was soon losing millions of dollars a day. Their owners, Warner Communications, became desperate to sell off the division.

The 1400XL and the 1450XLD had their delivery dates pushed back, and in the end, the 1400XL was cancelled outright, and the 1450XLD so delayed that it would never ship. Other prototypes which never made it to market include the 1600XL, 1650XLD, and 1850XLD. The 1600XL was to have been a dual-processor model capable of running 6502 and 80186 code, while the 1650XLD was a similar machine in the 1450XLD case. These were canceled when James J. Morgan became CEO and wanted Atari to return to its video game roots.[51] The 1850XLD was to have been based on the custom chipset in the Amiga Lorraine[52] (later to become the Commodore Amiga).

ANALOG Computing, writing about the 600XL in January 1984, stated that "the Commodore 64 and Tandy CoCo look like toys by comparison." The magazine approved of its not using the 1200XL's keyboard layout, and predicted that the XL's parallel bus "actually makes the 600 more expandable than a 400 or 800". While disapproving of the use of an operating system closer to the 1200XL's than the 400 and 800's, and the "inadequate and frankly disappointing" documentation, ANALOG concluded that "our first impression ... is mixed but mostly optimistic". The magazine warned, however, that because of "Atari's sluggish marketing", unless existing customers persuaded others to buy the XL models, "we'll all end up marching to the beat of a drummer whose initials are IBM".[47]

Although Commodore emerged intact from the computer price wars, conflict inside Commodore soon led to Jack Tramiel's ousting in January 1984. Looking to re-enter the market, he purchased the Atari consumer division in July 1984 from Warner for an extremely low price.[lower-alpha 7] When Tramiel took over, the high-end XL models were canceled and the low-end XLs were redesigned into the XE series. Nearly all Atari's research, design and prototype projects were cancelled, often with the new management ignorant of the nature of the projects. This included the Amiga-based 1850XLD system and other existing 68000 prototypes while Tramiel focused on developing the 68000-based Atari ST system and bringing in ex-Commodore engineers to work on the ST line.

Atari sold about 700,000 computers in 1984, compared to Commodore's two million.[53] As his new company prepared to ship the Atari ST in 1985, Tramiel stated that sales of Atari 8-bit computers were "very, very slow".[54] They were never an important part of Atari's business compared to video games, and it is possible that the 8-bit line was never profitable for the company despite selling almost 1.5 million computers by early 1986.[33][50][44]

By that year the Atari software market was decreasing in size. Antic magazine stated in an editorial in May 1985 that it had received many letters complaining that software companies were ignoring the Atari market, and urged readers to contact the companies' leaders.[55] "The Atari 800 computer has been in existence since 1979. Six years is a pretty long time for a computer to last. Unfortunately, its age is starting to show", ANALOG Computing wrote in February 1986. The magazine stated that while its software library was comparable in size to that of other computers, "now—and even more so in the future—there is going to be less software being made for the Atari 8-bit computers", warning that 1985 only saw a "trickle" of major new titles and that 1986 "will be even leaner".[56]

Computer Gaming World that month stated "games don't come out for the Atari first anymore".[57] In April the magazine published a survey of ten game publishers which found that they planned to release 19 Atari games in 1986, compared to 43 for Commodore 64, 48 for Apple II, 31 for IBM PC, 20 for Atari ST, and 24 for Amiga; only the Macintosh's 17 was fewer. Companies stated that one reason for not publishing for Atari was the unusually high amount of software piracy on the computer, partly caused by the Happy Drive.[58][59][60] The magazine warned later that year, "Is this the end for Atari 800 games? It certainly looks like it might be from where I write",[59] and in 1987 MicroProse explicitly denied rumors that it would release Gunship for the Atari, stating that the market was too small.[61] Lack of products remained a problem, Antic stating in May 1988 that "the biggest problem facing Atarians today is the difficulty of finding software and other products for our computers. Product unavailability is especially severe for the 8-bit Atari". The magazine urged readers to "SUPPORT Atari software publishers by buying the programs you want—DON'T trade illegal copies with your friends!"[62]

Atari 130XE

The 65XE and 130XE (XE stood for XL-Compatible Eight Bit)[63] were announced in 1985 at the same time as the initial models in the Atari ST series, and they visually resembled the ST. The 65XE has 64 KB of RAM and is functionally equivalent to the 800XL minus the PBI connection. The 130XE has 128 KB of memory, accessible through bank-selection. The 130XE was aimed to appeal at the mass market.[64]

The 130XE added the Enhanced Cartridge Interface (ECI), which is almost compatible with the Parallel Bus Interface (PBI), but physically smaller, since it is located next to the standard 400/800-compatible Cartridge Interface. It provides only those signals that did not exist in the latter. ECI peripherals were expected to plug into both the standard Cartridge Interface and the ECI port. Later revisions of the 65XE contain the ECI port as well.

The 65XE was marketed as 800XE in Germany and Czechoslovakia,[65] to ride on the popularity of the 800XL in those markets. All 800XE units contain the ECI port.[66]

Atari XE Game System

Atari released the XE Game System (Atari XEGS) in 1987. It is a repackaged 65XE with a removable keyboard.

ANTIC is a microprocessor which processes a sequence of instructions known as a display list. An instruction adds one row of the specified graphics mode to the display. Each mode varies based on whether it represents text or a bitmap, the resolution and number of colors, and its vertical height in scan lines. An instruction also indicates if it contains an interrupt, if fine scrolling is enabled, and optionally where to fetch the display data from memory.

Since each row can be specified individually, the programmer can create displays containing different text or bitmapped graphics modes on one screen, where the data can be fetched from arbitrary, non-sequential memory addresses.

ANTIC reads this display list and the display data using DMA (Direct Memory Access), then translates the result into a pixel data stream representing the playfield text and graphics. This stream then passes to GTIA which applies the playfield colors and incorporates Player/Missile graphics (sprites) for final output to a TV or composite monitor. Once the display list is set-up, the display is generated without any CPU intervention.

There are 15 character and bitmap modes. In low-resolution modes, 2 or 4 colors per display line can be set. In high-resolution mode, one color can be set per line, but the luminance values of the foreground and background can be adjusted. High resolution bitmap mode (320x192 graphics) produces NTSC artifacts which are "tinted" depending on the color values; it was normally impossible to get color with this mode on PAL machines.

For text modes, the character set data is pointed to by a register. It defaults to an address in ROM, but if pointed to RAM then a programmer can create custom characters. Depending on the text mode, this data can be on any 1K or 512 byte boundary. Additional register controls allow flipping all characters uspide down and toglging inverse video.

The Color Television Interface Adaptor[71] (CTIA) is the graphics chip used in early Atari 400/800 home computers. It is the successor to the TIA chip used in the Atari 2600. According to Joe Decuir, George McLeod designed the CTIA in 1977. The CTIA chip was replaced with the Graphic Television Interface Adaptor[71] (GTIA) in later revisions of the 400 and 800 and all other members of the Atari 8-bit family. GTIA, also designed by George McLeod, adds three new color interpretation modes for ANTIC's Playfield graphics that enables the display of more colors on the screen than previously available.[72]

The CTIA/GTIA receives Playfield graphics information from ANTIC and applies colors to the pixels from a 128 or 256 color palette depending on the color interpretation mode in effect. CTIA/GTIA also controls Player/Missile Graphics (aka sprites) functionality including collision detection between displayed objects (Players, Missiles, and ANTIC's Playfield), display priority control over objects, and color/luminance control of all displayed objects. CTIA/GTIA outputs separate digital luminance and chroma signals, which are mixed to form an analog composite video signal.

The CTIA/GTIA is responsible for reading the console keys Option, Select, Start, and operating the keyboard speaker in the Atari 400/800. In later computer models the audio output for the keyboard speaker is mixed with the audio out for transmission to the TV/video monitor. CTIA/GTIA is also responsible for reading the joystick triggers.

Certain 65XE and 800XE machines sold in Eastern Europe had a buggy GTIA chip, specifically those machines made in China in 1991.

The third custom support chip, named POKEY, is responsible for reading the keyboard, generating sound and serial communications (in conjunction with the PIA chip (Peripheral Interface Adapter, 6520) commands and IRQs, plus controlling the 4 joystick movements on 400/800 and later RAM banks and/or ROM(OS/BASIC/Self-test) enables for XL/XE lines[73]). It also provides timers, a random number generator (for generating acoustic noise as well as random numbers), and maskable interrupts. POKEY has four semi-independent audio channels, each with its own frequency, noise and volume control. Each 8-bit channel has its own audio control register which select the noise content and volume. For higher sound frequency resolution (quality), two of the audio channels can be combined for more accurate sound (frequency can be defined with 16-bit value instead of usual 8-bit). The name POKEY comes from the words "POtentiometer" and "KEYboard", which are two of the I/O devices that POKEY interfaces with (the potentiometer is the mechanism used by the paddle). The POKEY chip—as well as its dual- and quad-core versions—was used in many Atari coin-op arcade machines of the 1980s, including Centipede and Millipede,[74] Missile Command, Asteroids Deluxe, Major Havoc, and Return of the Jedi.

Production timeline dates retrieved from Atari 8-Bit Computers F.A.Q.,[66] and Chronology of Personal Computers.[75]

• 1400XL – Similar to the 1200XL but with a PBI, FREDDIE chip, built-in modem and a Votrax SC-01 speech synthesis chip. Cancelled.
• 1450XLD – a 1400XL with built-in 5¼″ disk drive and expansion bay for a second 5¼″ disk drive. Code named Dynasty. Made it to pre-production, but got abandoned by Tramiel.
• 1600XL – codenamed Shakti, this was dual-processor system with 6502 and 80186 processors and two built-in 5¼″ floppy disk drives.[76]
• 1850XL - codenamed Mickey, this was to use the "Lorraine" (aka "Amiga") custom graphics chips
• 900XLF – redesigned 800XLF. Became the 65XE.
• 65XEM – 65XE with AMY sound synthesis chip. Cancelled.
• 65XEP – "portable" 65XE with 3.5" disk drive, 5" green CRT and battery pack.

The startup screen of early Atari 8-bit models when no program is loaded. Memo Pad allows the user to type with the fullscreen editor.

The Atari 8-bit computers came with an operating system built into the ROM. The Atari 400/800 has two versions:

• OS Rev. A - 10 KB ROM (3 chips) early machines
• OS Rev. B - 10 KB ROM (3 chips) most common

The XL/XE all have OS revisions. This created compatibility issues with some of software. Atari responded with the Translator Disk, a floppy disk which loads the older 400/800 Rev. 'B' or Rev. 'A' OS into the XL/XE computers.

• OS Rev. 10 - 16 KB ROM (2 chips) for 1200XL Rev A
• OS Rev. 11 - 16 KB ROM (2 chips) for 1200XL Rev B (bug fixes)
• OS Rev. 1 - 16 KB ROM for 600XL
• OS Rev. 2 - 16 KB ROM for 800XL
• OS Rev. 3 - 16 KB ROM for 800XE/130XE
• OS Rev. 4 - 32 KB ROM (16 KB OS + 8 KB BASIC + 8 KB Missile Command) for XEGS

The XL/XE models that followed the 1200XL also have the Atari BASIC ROM built-in, which can be disabled at startup by holding down the silver OPTION key. Originally this was the notoriously buggy revision B. Later models have revision C.

The standard Atari OS only contained very low-level routines for accessing floppy disk drives. An extra layer, a disk operating system, was required to assist in organizing file system-level disk access. This was known as Atari DOS, and like most home computer DOSes of the era, had to be booted from floppy disk at every power-on or reset. Atari DOS was entirely menu-driven.

• DOS 1.0
• DOS 2.0S - Improved over DOS 1.0; became the standard for the 810 disk drive.
• DOS 3.0 - Came with 1050 drive. Uses a different disk format which is incompatible with DOS 2.0, making it unpopular.
• DOS 2.5 - Replaced DOS 3.0 with later 1050s. Functionally identical to DOS 2.0S, but able to read and write enhanced density disks.
• DOS XE - Designed for the XF551 drive.

Third-party replacement DOSes were also available.

GTIA modes are Antic Mode F displays with an alternate color interpretation option enabled via a GTIA register. The full color expression of these GTIA modes can be engaged in Antic text modes 2 and 3, though these will also requires a custom character set to achieve practical use of the colors.

• The Atari 800 Personal Computer System, by the Atari Museum, accessed November 13, 2008
• Goldberg, Marty; Vendel, Curt (2012). Atari Inc: Business is Fun. Syzygy Press. ISBN 9780985597405.
• Levy, Steven (1984). Hackers: Heroes of the Computer Revolution. Doubleday. ISBN 0-385-19195-2.
• Alcorn, Al (April 12, 2015). "ANTIC Interview 32 - Al Alcorn, Atari Employee #3". Antic (Interview). Interviewed by Randy Kindig.