The Atari ST was a series of personal computers made by Atari Corporation. It replaced the company's earlier 8-bit computers. The first model, the Atari 520ST, was released in limited amounts between April and June 1985 and became widely available in July. It was the first personal computer with a color graphical user interface that used a version of Digital Research's GEM environment, which was introduced in February 1985. The Atari 1040ST, released in 1986 with 1 MB of memory, was the first home computer with a cost per kilobyte of RAM under US$1/KB.

After Jack Tramiel bought the consumer division of Atari, Inc. in 1984 to form Atari Corporation, the 520ST was created in five months by a small team led by Shiraz Shivji. Along with the Macintosh, Amiga, Apple IIGS, and Archimedes, the ST was part of a group of mid-1980s computers that used 16 or 32-bit processors, had 256 KB or more of RAM, and included mouse-controlled graphical user interfaces. The "ST" in the name stands for "Sixteen/Thirty-two," which refers to the Motorola 68000 processor's 16-bit external bus and 32-bit internal components.

The ST was sold with either Atari's color monitor or a less expensive monochrome monitor. Color graphics modes were only available with the color monitor, while the highest-resolution mode required the monochrome monitor. Most models could display color modes on a television. In Germany and other markets, the ST became popular for computer-aided design and desktop publishing. Its built-in MIDI ports made it popular for music sequencing and controlling musical instruments among amateur and professional musicians. The Atari ST's main competitor was the Amiga from Commodore.

The 520ST and 1040ST were followed by the Mega series, the STE, and the portable STacy. In the early 1990s, Atari released three final versions of the ST with major technical changes compared to the original models: the TT030 (1990), the Mega STE (1991), and the Falcon (1992). Atari stopped making the ST line in 1993 and shifted its focus to the Jaguar video game console.

Development

The Atari ST was created because of competition between two companies, Atari, Inc. and Commodore International. Jay Miner, who helped design special chips for the Atari 2600 and Atari 8-bit computers, tried to convince Atari’s leaders to build a new chip for a video game console and computer. When his idea was not accepted, he left Atari in 1982 and started a small group called Hi-Toro. This group began working on a new chip called "Lorraine."

Hi-Toro later changed its name to Amiga, but it ran out of money to finish Lorraine. Atari, which was owned by Warner Communications at the time, paid Amiga to continue the work. In return, Atari got the right to use Lorraine for one year as a video game console. After that time, Atari could add a keyboard and sell the full computer, called the 1850XLD.

In January 1984, Jack Tramiel left Commodore International and formed a new company called Tramel Technology, Ltd. with his sons and other former Commodore workers. He planned a new computer and wanted to use Atari’s manufacturing and distribution network. In May and June 1984, he negotiated with Warner and bought Atari’s consumer division, which included the console and home computer departments. The arcade game division stayed with Warner. As people left Commodore to join Tramel Technology, Commodore sued four former employees for breaking trade secret agreements. Tramiel did not buy the employee contracts from Atari, so he rehired about 100 of the 900 former employees. Tramel Technology later changed its name to Atari Corporation.

While rumors spread that Tramiel was trying to buy Atari, Amiga Corp. began talks with Commodore. This led Commodore to want to buy Amiga outright, which would cancel any agreements with Atari. Instead of giving Lorraine to Atari, Commodore sent a $500,000 check to Amiga on Atari’s behalf, returning the money Atari had invested. Tramiel responded by suing Amiga Corp. on August 13, 1984, asking for money and a legal order to stop Amiga and Commodore from using the technology.

The lawsuit left the Amiga team without clear direction in mid-1984. Commodore continued its plans to improve the Lorraine chip and develop an operating system. In July 1985, Commodore announced the Amiga 1000 with the Lorraine chip, but it was not widely available until 1986. This delay allowed Atari to release the Atari 520ST in June 1985. In March 1987, the two companies settled their dispute in court without public details.

The main designer of the new computer project at Tramel Technology and Atari Corporation was Shiraz Shivji, a former Commodore employee who worked on the Commodore 64. Engineers considered different computer chips, including the 32-bit National Semiconductor NS32000, but were not satisfied with its performance. They switched to the Motorola 68000 chip. The Atari ST design was completed in five months in 1984 and was shown at the January 1985 Consumer Electronics Show.

A custom sound chip called AMY was being developed by Atari, Inc. and was considered for the ST. However, it was not finished in time, so Atari used a different chip, the Yamaha YM2149F version of the General Instrument AY-3-8910.

After buying Atari, Microsoft suggested to Tramiel that it could move Windows to the Atari platform, but the timeline was delayed by two years. A proposal to create a new operating system was rejected because Atari’s leaders were unsure if the company had the needed skills.

Digital Research was working on a new system called Crystal, which later became GEM. However, the company was focused on the Intel platform. A team from Atari visited Digital Research’s headquarters to help port GEM to the Motorola 68000 chip. Atari’s Leonard Tramiel oversaw "Project Jason" (also called "The Operating System") for the ST series, named after designer Jason Loveman.

GEM is based on CP/M-68K, a version of CP/M for the 68000 chip. By 1985, CP/M was becoming outdated because it did not support features like subdirectories. Digital Research was also working on GEMDOS, a disk operating system for GEM, and debated whether it could be completed in time for product delivery in June. They decided to port it, creating a GEMDOS file system that became part of Atari TOS (short for "The Operating System"). This gave the ST a fast, organized file system needed for hard drives and provided programmers with tools similar to MS-DOS. The Atari ST’s character set uses codepage 437.

Release

After six months of hard work following Tramiel's takeover, Atari introduced the 520ST at the Winter Consumer Electronics Show in Las Vegas in January 1985. InfoWorld described the prototypes shown at computer shows in this way:

Atari surprised people by showing the ST at Atlanta COMDEX in May. The ST looked similar to the original Macintosh, and Tramiel's involvement in its creation led to it being called "Jackintosh." Many were impressed by how quickly Atari developed the ST, but others were unsure, pointing to its simple design, Atari's financial problems, and poor relationships between Tramiel's company, Commodore, and software developers.

In early 1985, the 520ST was sent to the press, developers, and user groups. It became available for sale to the public in early July 1985. This helped save the company. Atari's advertisements said, "America, We Built It For You," and quoted Atari president Sam Tramiel: "We promised. We delivered. With pride, determination, and good old ATARI know how." By November, Atari reported that more than 50,000 520STs had been sold, with U.S. sales reaching over 50,000 units. The machine moved from idea to store shelves in less than a year.

Atari planned to release the 130ST with 128 KB of RAM and the 260ST with 256 KB. However, the ST initially did not have TOS in its memory and needed to load TOS from a floppy disk, which used 206 KB of memory that could have been used for other programs. The 260ST was sold in Europe on a limited scale. Early models had six memory slots for easy upgrades to TOS. Later, new TOS versions were released and included in new machines or offered as upgrades for older ones.

Atari originally planned to include GEM's Graphical Device Operating System (GDOS), which allows programs to send GEM VDI (Virtual Device Interface) commands to drivers loaded by GDOS. This lets developers send VDI instructions to other devices by pointing to them. However, GDOS was not ready when the ST started shipping and was later included in software packages and with later ST models. Later GDOS versions supported vector fonts.

A limited set of GEM fonts was included in the ST's memory, including its standard 8×8 pixel graphical character set. This set included four characters that could be arranged to form the face of J. R. "Bob" Dobbs, a figure from the Church of the SubGenius.

The ST was less expensive than many similar computers, such as the Macintosh Plus, and faster than many others. Because of its price and performance, the ST became popular, especially in Europe where exchange rates made other computers more expensive. Atari's advertising slogan at the time was "Power Without the Price." An Atari ST with terminal software was much cheaper than a Digital VT220 terminal, which was often needed by offices with central computers.

By late 1985, the 520ST added an RF modulator for displaying images on a television.

Computer Gaming World noted that Tramiel's poor reputation before joining Atari might make stores unwilling to sell the ST, hurting its availability. One retailer said, "If you can believe Lucy when she holds the football for Charlie Brown, you can believe Jack Tramiel." Another said, "Our interest in Atari is zero, zilch." Neither Atari nor Commodore could convince large chains like ComputerLand or BusinessLand to sell their products. Observers criticized Atari's unclear plans for the ST, as it changed its strategies between using mass retailers, specialty stores, and both. At COMDEX, Atari executives could not name any stores that would sell the ST. After meeting with Atari, one analyst said, "We've seen marketing strategies changed before our eyes."

Tramiel's reputation affected software developers. One said, "Dealing with Commodore is like dealing with Attila the Hun. I don't know if Tramiel will follow his old habits… I don't see a lot of people rushing to get software on the machine." Large companies like Lotus, Ashton-Tate, and Microsoft did not promise software for the ST or Amiga, and most companies hesitated to support platforms other than the IBM PC, Apple, and Commodore 64. Philippe Kahn of Borland said, "These days, if I were a consumer, I'd stick with companies like Apple and IBM that I know will be around."

At Las Vegas COMDEX in November 1985, more than 30 companies showed ST software, while the Amiga had almost none. After Atlanta COMDEX, The New York Times reported that "more than 100 software titles will be available for the [ST], most written by small software houses that desperately need work," and contrasted the "small, little-known companies" at Las Vegas with larger ones like Electronic Arts and Activision, which planned Amiga applications.

Trip Hawkins of Electronic Arts said, "I don't think Atari understands the software business. I'm still skeptical about its resources and its credibility." Although Michael Berlyn of Infocom promised to publish all his games for the ST, he doubted others would do so quickly. Spinnaker and Lifetree were more positive, both promising to release ST software. Spinnaker said, "Atari has a vastly improved attitude toward software developers. They are eager to give us technical support and machines." Lifetree said, "We are giving Atari high priority." Some, like Software Publishing Corporation, were unsure whether to develop for the ST or Amiga. John C. Dvorak wrote that the public saw both Commodore and Atari as selling "cheap disposable" game machines, partly because of their computers' advanced graphics.

Design

The original 520ST computer case was designed by Ira Velinsky, Atari's chief industrial designer. It has a wedge shape with sharp, angular lines and openings on the back for airflow. The keyboard has a soft feel when typing and diamond-shaped function keys at the top. It is an all-in-one unit, like the Commodore 64, but with a larger keyboard that includes arrow keys and a numeric keypad. The 520ST has an external floppy disk drive (SF354) and a power adapter. Starting with the 1040ST model, the floppy drive and power supply are built into the main unit.

The ports on the 520ST remained mostly the same throughout its production.

• RS-232c serial port (DB25 male, used for basic 9-conductor data transfer)
• Centronics printer port (DB25 female, works with basic one-way printing but can also be used for game controls with special adapters)
• Atari joystick ports (DE-9 male, for the mouse and game controllers)
• 2 MIDI ports (5-pin DIN, labeled "IN" and "OUT")

Because the Centronics printer port can work both ways, it was sometimes used for joystick input. Some games used adapters that connected to the printer port, adding two more 9-pin joystick ports.

• Monitor port (custom 13-pin DIN, with 12 pins in a rectangle, supporting signals for both color and black-and-white monitors, audio, and later models with composite video)
• ACSI port (similar to SCSI, custom 19-pin D-sub, for hard drives and laser printers, capable of transferring up to 2 MB/s with proper programming)
• Floppy port (14-pin DIN, operating at 250 kbit/s)
• ST cartridge port (double-sided 40-contact edge connector, for 128 KB ROM cartridges)

The Atari ST can connect to either a black-and-white or color monitor. The color monitor supports two resolutions: 320 × 200 pixels with 16 of 512 colors, and 640 × 200 pixels with 4 of 512 colors. The black-and-white monitor is less expensive and has one resolution: 640 × 400 pixels at 71.25 Hz. The type of monitor connected determines which resolutions are available, so software either supports both or only one. Most games require a color monitor, while productivity programs often use the black-and-white version. The Philips CM8833-II was a popular color monitor for the Atari ST.

Atari first used single-sided 3.5-inch floppy disk drives that could store up to 360 KB. Later models used double-sided drives, storing 720 KB. Some software, especially games, was released on single-sided disks, providing two 360 KB disks instead of one 720 KB disk to avoid confusing early users.

Some software uses formats that let double-sided drives read the full disk but allow single-sided drives to only read side A. Many magazine cover disks (like the first 30 issues of ST Format) and some games used this method. For example, the music in Carrier Command and the intro in Populous cannot be read by single-sided drives.

ST computers with double-sided drives can read disks formatted by MS-DOS, but IBM PC-compatible computers cannot read Atari disks because of differences in how data is arranged on track 0.

Later systems

In 1986, Atari improved the basic design with the 1040STF, named 1040ST. This model had twice the memory (RAM) of the 520ST and included a built-in power supply and double-sided floppy drive with twice the storage capacity. These changes made the machine larger but reduced the number of cables needed. The joystick and mouse ports, which were on the right side of earlier models, were moved to a recess under the keyboard. An "FM" version added an RF modulator, allowing users to connect a television instead of a monitor.

The letters "F" and "FM" were often not used in everyday language. In March 1986, BYTE magazine's cover photo showed the system as 1040ST, but the article referred to it simply as "1040ST."

The 1040ST was one of the first personal computers to ship with 1 MB of RAM as standard. It had a list price of $999 in the United States (about $2,900 in today's money). BYTE magazine called it the first computer to break the $1,000 per megabyte price barrier. Compute! magazine noted that the 1040ST was the first computer with 1 MB of RAM to sell for less than $2,500.

A limited number of 1040STFs came with a single-sided floppy drive that stored 360KB, compared to 720KB in the double-sided version.

Sales of the 1040ST were strong, especially in Europe, where Atari sold 75% of its computers. West Germany became Atari's largest market, with small business owners using the computers for tasks like desktop publishing and CAD (computer-aided design).

To meet demand, Atari introduced the ST1 at Comdex in 1986. It was later renamed the Mega. The Mega had a high-quality keyboard, a stronger case to support a monitor, and an internal bus expansion connector. An optional 20 MB hard drive could be placed above or below the main case. The Mega initially had 2 or 4 MB of RAM, with a 1 MB version called the Mega 1. It could be paired with Atari's laser printer for a low-cost desktop publishing package.

A special chip called a blitter coprocessor improved some graphics performance, but it was not included in all models. Developers had to check for its presence in their programs. Applications using the GEM API automatically used the blitter.

In late 1989, Atari released the 520ST and 1040ST (also called STE), which were improved versions of the ST. These models had better multimedia features, including a larger color palette of 4,096 colors (though only 16 could be used in the lowest resolution). They also added genlock support and a blitter coprocessor (called "BLiTTER"), which could move large amounts of data quickly. The STE was the first Atari computer with PCM audio, allowing playback of 8-bit samples at various frequencies using direct memory access (DMA). The audio channels could be arranged as mono or LRLRLRLR… bytes. Upgrading RAM became easier with SIMMs.

Two improved joystick ports were added, placed in more accessible locations on the side of the case. These ports were later used in the Atari Jaguar console and were compatible with existing joysticks.

Early STE models had software and hardware conflicts, causing some applications and games to malfunction. This was often due to programs accessing hardware directly instead of using the operating system. Some applications, like the word processor 1st Word Plus, had issues when a joystick was connected. The only major game released exclusively for the STE was Sleepwalker. Other games, such as Another World, Zool, and The Chaos Engine, had improvements for the STE.

The last STE model, the Mega STE, was an STE in a gray Atari TT case. It had a switchable 16 MHz, dual-bus design (16-bit external, 32-bit internal), an optional Motorola 68881 FPU, a built-in 1.44 MB floppy drive, a VME expansion slot, a network port, and an optional hard drive. It came with TOS 2.00, which improved hard drive support and added features like a better desktop interface. It was marketed as more affordable than the TT but more powerful than a standard ST.

In 1990, Atari released the high-end TT030 workstation, based on a 32 MHz Motorola 68030 processor. The name "TT" referred to the 32-bit internal and external buses of the 68030 chip. The TT had improved graphics and more powerful support chips, along with a new case design that included an integrated hard drive enclosure.

The final ST model was the Falcon030, also based on the 68030 processor but running at 16 MHz. It had improved video modes and an on-board Motorola 56001 audio digital signal processor. Like the STE, it supported sampling frequencies above 44.1 kHz. It could play and record audio using 8 mono or 4 stereo channels. The Falcon used a 16-bit bus instead of a 32-bit one, which reduced performance but lowered costs. It was sold in a budget-friendly case similar to earlier ST models. Aftermarket kits allowed users to upgrade to a desktop or rack-mount case with a separate keyboard.

Released in 1992, the Falcon was discontinued by Atari the following year. In Europe, C-Lab licensed the Falcon design and released the C-Lab Falcon Mk I, which was nearly identical to Atari's Falcon but had minor audio changes. The Mk II added a 500 MB SCSI hard drive, and the Mk X included a desktop case. Some C-Lab Falcons were sold in the United States through Atari dealers.

Software

Software publishers were hesitant to create games and programs for the Atari ST because they believed there was more software piracy than usual. In 1988, a magazine called Compute! reported that some companies thought pirate bulletin board systems (BBSs) were sharing software without permission. This led to warnings that piracy could harm the Atari ST's future. A review of a game called Typhoon Thompson noted that piracy was a major issue.

In 1989, a letter from Gilman Louie, who led a company called Spectrum HoloByte, explained that competitors warned him that releasing a game like Falcon on the Atari ST would fail because pirates would share it widely. Within 30 days of its release, the game was already on BBSs. Louie said the Atari ST market was smaller than the IBM PC market, making it easier for pirates to spread software. He also noted that the Amiga version of Falcon sold twice as much in six weeks as the Atari ST version did in nine weeks. The Mac and PC versions sold four times more. A gaming magazine called Computer Gaming World said Louie’s explanation was the clearest reason why fewer games were made for the Atari ST.

Several operating systems were created for or adapted to the Atari ST. These included Unix-like systems such as Idris, Minix, and MiNT OS, which was designed specifically for the Atari ST.

The Atari ST’s MIDI ports allowed professional music software to be developed. Early versions of popular programs like Cubase and Logic Pro were available on the Atari ST. A program called KCS let users run other applications, such as synthesizer tools, while using the sequencer. Another program, MasterTracks Pro, started on the Apple II and later had versions for the Atari ST and IBM PC. It continued on Windows and macOS.

Music tracker software like TCB Tracker helped users create music for the Yamaha synthesizer, now called chiptunes.

The Atari ST had more memory than other computers of its time, making sound sampling possible. A program called Replay Professional used the ST’s cartridge port to read sound and output it through the on-board frequency.

Professional desktop publishing tools included Timeworks Publisher, PageStream, and Calamus. Word processors available were WordPerfect, Microsoft Write, AtariWorks, Signum, Script, and First Word. Spreadsheets included 3D-Calc, and databases included Zoomracks. Graphics tools included NEOchrome, DEGAS & DEGAS Elite, Deluxe Paint, STAD, and Cyber Paint. The Spectrum 512 paint program used rapid palette switching to display 512 colors on screen.

3D graphics software like Cyber Studio CAD-3D allowed users to create 3D models and animations. Video editing tools used dongles connected to the cartridge port but had limited features, such as low frame rates and monochrome images. Later, Spectrum 512 and CAD-3D worked together to create realistic 3D images with 512 colors, though processing was slow.

Garry Kasparov, a famous chess player, helped create the first version of ChessBase, a program for storing chess game records. He called this development "the most important in chess research since printing."

Touchscreen point-of-sale software for restaurants was first developed for the Atari ST by Gene Mosher. He used a custom GUI instead of the standard GEM interface.

The Atari ST came with Digital Research Logo and Atari ST BASIC. Later, better BASIC systems like HiSoft BASIC, GFA BASIC, and Omikron BASIC were released. In Germany, Omikron BASIC was included with the Atari ST.

Atari’s first development kit cost $5,000 (about $14,686 in 2025) and included a computer and manuals. A later kit cost $300 and included software tools like a C compiler and debugger. A third-party kit called Megamax C cost $200.

Other tools included assemblers, Pascal and Modula-2 compilers, and programming languages like C, LISP, and Prolog.

The Atari ST was successful in gaming because it was affordable, fast, and had colorful graphics compared to older systems. Developers like Steve Bak, Peter Molyneux, and Jeff Minter created games for the ST.

When the Atari ST was released in 1985, it seemed aimed at professionals. However, features like two joystick ports and a 320×200 pixel display with 16 colors hinted at its gaming potential. Early games did not show major improvements over 8-bit systems, but later games like Arena, Megaroids, and Joust demonstrated the ST’s capabilities.

As developers learned more about the ST, they created games with advanced graphics and sound. Examples include Goldrunner, which used sampled sound and smooth scrolling, and Starglider, which had a long audio sample and fast, colorful 3D graphics.

Music industry

The Atari ST's low cost, built-in MIDI ports, and fast, responsive performance made it popular among musicians.

• Aleksandr Zatsepin, a well-known Russian film and song composer, began using personal computers with the Atari 1040ST for his work and continued using Cubase and the Vienna Symphonic Library.
• German electronic music pioneers Tangerine Dream used the Atari ST extensively in their studio and for live performances during the late 1980s and 1990s.
• The album Earth Moving by Mike Oldfield was recorded using an Atari ST and C-Lab MIDI software.
• The Fatboy Slim album You've Come a Long Way, Baby was created using an Atari ST.
• During the Paris performance of Jean Michel Jarre's album Waiting for Cousteau, known as Paris La Défense – Une Ville En Concert, musicians connected Atari ST machines with C-Lab Unitor software to their keyboards, as shown in TV broadcasts and video recordings.
• White Town's song "Your Woman," which reached No. 1 in the UK singles charts, was created using an Atari ST.
• The Utah Saints used a 520ST and 1040ST running Cubase during the recording of their albums Utah Saints and Two. Their 1040ST was still used occasionally for re-recording or remixing early tracks up to 2015.
• Atari Teenage Riot programmed most of their music on an Atari ST, including the entire album Is This Hyperreal? (June 2011).
• Richard H. Kirk, founder of Cabaret Voltaire, said in 2016 that he continues to write music on an Atari 1040ST with C-Lab.
• The artist known as Darude used Cubase on an Atari 1040ST when he created his 2000 hit "Sandstorm."
• Depeche Mode used an Atari ST and Cubase in the studio during the production of Songs of Faith and Devotion in 1992. The machine is visible in the documentary included with the 2006 remaster of the album.
• Record producer Jimmy Hotz used an Atari ST to produce Fleetwood Mac's Tango in the Night album, as well as recordings for B. B. King and Dave Mason.
• English DJ and house producer Joey Negro.
• English songwriters and record producers Stock, Aitken, and Waterman.
• English synth-pop duo Pet Shop Boys replaced their Fairlight CMI with an Atari ST. Their programmer, Pete Gleadall, said, "[Atari ST] was just much easier to work with."
• Canadian industrial band Skinny Puppy used the Atari ST with Steinberg Pro 24 software to produce several albums, including Rabies and The Process. A 1040ST is visible in footage of the band jamming in their studio during the writing sessions for The Process.
• Dario G used the Atari ST to produce the dance track "Sunchyme," which reached No. 2 in the UK charts.

Technical specifications

All ST computers use both custom-designed and commercially available chips.

Custom Chips:
– ST Shifter (Video Shift Register Chip): This chip helps create bitmap graphics using 32 KB of memory that is all in one continuous block. The screen address must be a multiple of 256.
– ST GLU (Generalized Logic Unit): This chip controls how the system connects its other chips. It does not handle data movement but helps link chips together.
– ST MMU (Memory Management Unit): This chip sends signals to the CPU, blitter, and DMA to access dynamic RAM. Even memory access times are used by the CPU, blitter, or DMA, while odd times are used for refreshing DRAM or displaying screen content.
– ST DMA (Direct Memory Access): This chip transfers data between floppy or hard drives and the main memory of the ST.

Support Chips:
– MC6850P ACIA (Asynchronous Common Interface Adapter): This chip allows the ST to communicate directly with the keyboard and MIDI devices. It uses 7812.5 bits per second for the keyboard and 31.250 kilobits per second for MIDI.
– MC68901 MFP (Multi Function Peripheral): This chip handles interrupts, serial communication, and other control signals. The Atari TT030 uses two of these chips.
– WD-1772-PH (Western Digital Floppy Disk Controller): This chip controls the floppy disk drive.
– YM2149F PSG (Programmable Sound Generator): This chip creates three-voice sound, controls floppy disk signals, serial communication, and printer output.
– HD6301V1 (Hitachi Keyboard Processor): This chip scans the keyboard and manages mouse and joystick ports.

Original 520ST Specifications:
– CPU: Motorola 68000, a 16- or 32-bit processor running at 8 MHz. It uses 16-bit data, 32-bit internal processing, and 24-bit addressing.
– RAM: 512 kilobytes or 1 megabyte.
– Display Modes:
– Low resolution: 320 × 200 pixels (16 colors), with 512 colors available.
– Medium resolution: 640 × 200 pixels (4 colors), with 512 colors available.
– High resolution: 640 × 400 pixels (monochrome).
– Sound: Yamaha YM2149 chip provides three-voice square wave sound and one-voice white noise.
– Drive: Single-sided 3 1/2-inch floppy disk drive with 360 kilobytes of storage when formatted.
– Ports:
– TV output (on ST-M and ST-FM models, using NTSC or PAL standards).
– MIDI in/out with "out-thru" functionality.
– RS-232 serial port.
– Centronics parallel port (printer).
– Monitor output (RGB or Composite Video, 13-pin DIN).
– Extra disk drive port (14-pin DIN).
– DMA port (ACSI interface) for hard disks and Atari Laser Printer (shares memory with the computer).
– Joystick and mouse ports (9-pin MSX standard).
– Operating System: TOS v1.00 with Graphics Environment Manager (GEM).

Early models had the operating system stored on a floppy disk until a final version was placed in ROM. This version of TOS was started using a small boot ROM.

In 1986, most models became STs with either a single-sided (520STF) or double-sided (1040STF) double-density floppy disk drive built-in. No other changes were made. Also in 1986, the 520ST (or 520STM) added an RF modulator to allow color display on a TV. Later F and FM models of the 520ST had a built-in double-sided floppy disk drive instead of a single-sided one.

Original 520ST/1040ST Specifications:
– All features of the 520STFM/1040STFM.
– Expanded color palette with 4,096 colors available.
– Blitter Chip (BLiTTER): This chip copies, fills, or clears large data blocks at a maximum speed of 4 megabytes per second.
– Hardware Support: Enables fine horizontal and vertical scrolling, and split-screen display using the Shifter video chip.
– DMA Sound Chip: Provides two-channel stereo 8-bit PCM sound at 6.25/12.5/25/50 kHz with stereo RCA audio outputs. This uses enhancements to the Shifter video chip.
– National LMC 1992 Audio Controller: Adjusts left/right/master volume and bass/treble using a Microwire interface.
– Memory: 30-pin SIMM slots (SIPP packages in early versions) allow upgrades up to 4 MB. Supported sizes include 0.5, 1.0, 2.0, 2.5, and 4.0 MB. Later third-party upgrades allow up to 14 MB with the Magnum-ST, replacing the MMU and adding extra chips.
– Video Synchronization: Allows external devices to sync with the computer for video Genlock use.
– Analog Joypad Ports (2): Supports paddles, light pens, joysticks, and joypads. Atari Jaguar and Power Pad joypads work without adapters. Two Atari-style digital joysticks can be used per port with an adapter.
– Operating System: TOS 1.06 (also called TOS 1.6) or TOS 1.62 (fixes compatibility issues) stored in two socketed 128 KB ROM chips.
– Socketed PLCC 68000 CPU: Allows easy replacement of the CPU.

Models

The members of the ST family are listed below, in roughly the order they were created:

The 130ST was planned to be a version with 128 KB of memory. It was introduced at the 1985 Consumer Electronics Show along with the 520ST, but it was never made. The 4160ST was similar to the 1040ST but had 4 MB of RAM. A few test models were created, but the system was not officially sold. Atari made some metallic case badges labeled "4160STE" and gave them to dealers. These badges are sometimes found on systems that were originally 520/1040STE. No similar labels were made for the base of the systems.

The Atari Transputer Workstation was a self-contained computer created with Perihelion Hardware. It used modified ST hardware and could include up to 17 transputers, which allowed it to perform complex tasks like ray tracing.

After Atari left the computer market, two companies, Medusa Computer Systems and Milan Computer, made machines compatible with the Atari Falcon and TT models. These machines used 68040 and 68060 processors. The FireBee is a copy of the Atari ST/TT model that uses a Coldfire processor. The GE-Soft Eagle is a version of the TT model that runs at 32 MHz.

Peripherals

• SF354: Single-sided floppy drive for 3 1⁄2-inch disks (360 KB), with an external power supply
• SF314: Double-sided floppy drive for 3 1⁄2-inch disks (720 KB), with an external power supply
• PS3000: Combined 12-inch color monitor and 360 KB 3 1⁄2-inch floppy drive (SF354). Includes a speaker. Made by JVC in limited numbers (about 1,000 units), with only a few working models remaining.
• SM124: Monochrome monitor with a 12-inch screen (9.5-inch displayed image), speaker, 640 × 400 pixels, and 70 Hz refresh rate
• SM125: Monochrome monitor with a 12-inch screen, swivel stand for up/down/sideways movement, speaker, 640 × 400 pixels, and 70 Hz refresh rate
• SM147: Monochrome monitor with a 14-inch screen, no speaker, and designed to replace the SM124
• SC1224: Color monitor with a 12-inch screen, 640 × 200 pixels, and a speaker
• SC1425: Color monitor with a 14-inch screen, one speaker on the left side, and a jack for connecting ear-listeners
• SC1435: Color monitor with a 14-inch screen, stereo speakers, and designed to replace the SC1224 (rebuilt version of the Magnavox 1CM135)
• SM195: Monochrome monitor with a 19-inch screen for the TT030 computer, 1280 × 960 pixels, and 70 Hz refresh rate
• SH204: External hard drive with a 20 MB MFM drive, housed in a metal "shoe box" case
• SH205: External hard drive with a 20 MB MFM drive, compatible with Mega ST cases, and using a 3.5-inch (Tandon TM262) or 5.25-inch (Segate ST225) drive with an ST506 interface (later renamed Megafile 20)
• Megafile 20, 30, 60: External hard drives with Mega ST cases, using the ACSI bus; Megafile 30 and 60 include 5.25-inch RLL drives (often Seagate ST238R 30 MB or Seagate ST277R 60 MB) with an ST506 interface
• Megafile 44: Removable cartridge drive with an ACSI bus and Mega ST case
• SLM804: Laser printer connected through the ACSI DMA port, using the ST computer’s memory and processor to create pages for printing
• SLM605: Laser printer connected through the ACSI DMA port, smaller than the SLM804

SatanDisk is an adapter for SD and MMC cards used with Atari 16-bit computers, such as the Atari ST. Created in 2007, it was designed to replace older mechanical hard drives from Atari (SH204, SH205, and Megafile) and compatible devices. The adapter connects an SD or MMC card to the ACSI port of Atari computers and works with TOS versions 1.02 to 2.06. It supports up to 4 GB of storage and appears to the system as a regular ACSI hard disk. It requires the proprietary HDDriver software package to function.

In 2009, the developer Jookie (Miroslav NOHAJ) introduced UltraSatan, a newer version of the adapter. UltraSatan supports two SD/MMC cards at the same time, allows cards to be inserted or removed while the system is running, and includes a battery-powered clock chip. It works with both the commercial HDDriver software and the free ICD PRO software.