The Atari 8-bit computers, formally launched as the Atari Home Computer System, are a series of home computers introduced by Atari, Inc., in 1979 with the Atari 400 and Atari 800.Atari's PC Evolution The History of Atari Computers, Benj Edwards, PC World April 21, 2011, retrieved August 20 2016. The architecture is designed around the 8-bit MOS Technology 6502 CPU and three custom coprocessors which provide support for sprites, smooth multidirectional scrolling, four channels of audio, and other features. The graphics and sound are more advanced than most of its contemporaries, and video games are a key part of the software library. The 1980 first-person space combat simulator Star Raiders is considered the platform's killer app.
The Atari 800 was positioned as a high-end model and the 400 as more affordable. The 400 has a pressure-sensitive, spillproof membrane keyboard and initially shipped with a non-upgradable of RAM. The 800 has a conventional keyboard, a second cartridge slot, and allows easy RAM upgrades to 48KB. Both use identical 6502 CPUs at ( for PAL versions) and coprocessors ANTIC, POKEY, and CTIA/GTIA. The plug-and-play peripherals use the Atari SIO serial bus, and one of the SIO developers eventually went on to co-patent USB (Universal Serial Bus). The architecture of the Atari 8-bit computers was reused in the 1982 Atari 5200 game console, but games for the two systems are incompatible.
The 400 and 800 were replaced by multiple computers with identical core technology and different presentation. The 1200XL was released in early 1983 to supplant the 800. It was discontinued in June 1983, but the industrial design carried over to the 600XL and bestselling 800XL released later the same year. After the company was sold and reestablished, Atari Corporation released the 65XE (called the 800XE in some European markets) and 130XE in 1985. The XL and XE are lighter in construction, have two joystick ports instead of four, and Atari BASIC is built-in. The 130XE has 128 KB of bank-switched RAM. In 1987, after the Nintendo Entertainment System reignited the console market, Atari Corporation packaged the 65XE as a game console, with an optional keyboard, as the Atari XEGS. It is compatible with 8-bit computer software and peripherals.
The 8-bit computers were sold both in computer stores and department stores such as Sears using an animated demo to attract customers. Two million Atari 8-bit computers were sold during its major production run between late 1979 and mid-1985. The primary global competition came when the similarly equipped Commodore 64 was introduced in August 1982. In the latter half of the 1980s, the 800XL was the leading home computer in Eastern Bloc countries. In 1992, Atari Corporation officially dropped all remaining support for the 8-bit line.
History
Design of the "Home Computer System" started at Atari as soon as the Atari Video Computer System was released in late 1977. While designing the VCS in 1976, the engineering team from Atari Grass Valley Research Center (originally Cyan Engineering) said the system would have a three-year lifespan before becoming obsolete. They started planning for a console that would be ready to replace it around 1979.
Because of decisions made while designing the VCS, it could not be expanded into a backwards-compatible home computer. Atari developed essentially a greatly updated version of the VCS, fixing its major limitations, but sharing a similar philosophy; the coin-op division offered many suggestions. The newer design has better speed, graphics, and sound. Work on the chips for the new system continued throughout 1978 and focused on a much-improved video coprocessor known as the CTIA (the VCS version was the TIA).
During the early development period, the home computer era began in earnest with the TRS-80, PET, and Apple II—what Byte magazine dubbed the "1977 Trinity". Nolan Bushnell sold Atari to Warner Communications for in 1976 to fund the launch of the VCS. In 1978, Warner hired Ray Kassar as CEO of Atari. Kassar wanted the chipset used in a home computer to challenge Apple, so it needed character graphics, some form of expansion for peripherals, and run the then-universal BASIC programming language.
Atari engineer Jay Miner created a two chip display architecture for the Atari 8-bit computers. The CTIA chip handles sprites and background graphics, but to reduce load on the main CPU, loading video registers and buffers is delegated to a dedicated microprocessor, the Alphanumeric Television Interface Controller or ANTIC. CTIA and ANTIC work together to produce a complete display, with ANTIC fetching scan line data from a framebuffer and sprite memory in RAM, plus character set bitmaps for character modes, and feeding these to the CTIA. CTIA processes the sprite and playfield data via its own color, sprite, and graphics registers to produce the final color video output.
Development
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). Atari would market Colleen as a computer and Candy as a game machine or hybrid game console. Colleen includes 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 suitable for superior 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 for 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.
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?" For example, cartridges were expected to make the computers easier to use. To minimize handling of bare circuit boards or chips, as is 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 disk operating 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" which is a built-in full-screen editor without file storage support.
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. By the summer of 1978, education had become a focus for the new systems. The Colleen design was largely complete by May 1978, but in early 1979 the decision was made that Candy would also be a complete computer, but intended for children. As such, it would feature a new keyboard designed to be resistant to liquid spills; the membrane keyboard "didn't feel great, but it worked", Decuir said. Another reason for including a keyboard on Candy was strong initial reaction to Star Raiders.
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.
FCC issues
Televisions of the time normally had only one input: the antenna connection. For devices like a computer, the video is generated and then sent to an RF modulator to convert it to antenna-like output. The introduction of many game consoles during this era led to situations where poorly designed modulators generated so much signal as to cause interference with other nearby televisions, even in neighboring houses. In response to complaints, the Federal Communications Commission (FCC) introduced new testing standards which are extremely exacting and difficult to meet.
To meet the FCC requirements, both new machines were built around cast aluminum shields forming a partial Faraday cage, with the various components screwed onto this internal framework. This resulted in a sturdy computer, at the disadvantage of added manufacturing expense and complexity.
The FCC ruling also made it difficult to have any sizable holes in the case, which would allow RF leakage. This 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 system for daisy-chaining multiple, auto-configuring devices to the computer through a single shielded connector. The internal slots are reserved for ROM and RAM modules; they do 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.
400 and 800 release
After Atari announced its intent to enter the home computer market in December 1978, the Atari 400 and Atari 800 were presented at the Winter CES in January 1979 and shipped in November 1979.
Their 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 caused overheating issues, so the casings were removed. Later, the expansion cover was held down with screws instead of the easier-to-open plastic latches. The computers eventually shipped with maxed-out RAM: 16k and 48k, respectively, using 16kx1 DRAMs.
Both models have four joystick ports, permitting four simultaneous players, but only a few games (such as M.U.L.E.) use them all. Paddle controllers are wired in pairs, and Super Breakout supports eight players. The Atari 400, with a membrane keyboard and single internal ROM slot, outsold the Atari 800 by a 2-to-1 margin. Only one cartridge for the 800's right slot was produced by March 1983, and later machines in the series have only one slot.