When work started on the follow-up to the VCS in 1977, the engineering team Joe Decuir, Jay Miner, and Steve Mayer were tasked to create a machine that could both follow up the VCS, and double as an entry into the burgeoning personal computer market.
"(The follow-up had to) support 1978-vintage arcade games. We knew we would need to leapfrog the 2600 before somebody else did. (It also had to) support home computer character and bitmap graphics. We saw the Apple II, Commodore, and Radio Shack appliance machines coming." xxxiii
- Joe Decuir
The project was soon split into two separate projects, dubbed "Colleen" and "Candy" after two particularly attractive secretaries These products were later re-named the Atari 800 and 400 respectively. "Colleen" was to be the full-fledged computer, while "Candy" was more suited as the game machine follow-up to the 2600.
Both were based on the same basic hardware design with four separate silicon chips that handled different parts of the computer's operation: the 6502 CPU running at 1.8 MHz, the ANTIC display microprocessor, CTIA graphics chip, and POKEY sound chip. The power of these multiple processors pushed the 8-bit computers power far beyond that of the VCS.
Jay Miner, as system architect, led a group that included Joe Decuir, George McCloud and Francois Michel that designed the ANTIC microprocessor for processing display information and the CTIA graphics chip to put it on a screen xxxiv.
It was a very potent combination, giving the Colleen and Candy the most sophisticated graphics for any microcomputer at the time. The ANTIC took graphics information in the form of Display Lists. Display List Interrupts allowed the screen to be cut horizontally into multiple parts, allowing for almost limitless display options.
These instructions were processed and displayed by one of multiple graphics modes by the CTIA (later GTIA) processor. The design also included hardware based sprites (Player-Missile Graphics) for creating games, a character-set that could be completely redefined in code, and per-line fine scrolling. xxxv In terms of sheer horsepower, the graphics capabilities of these new machines made the output of the TIA chip in the VCS look primitive by comparison.
After the 6502, ANTIC and CTIA, the 4th chip of the design was the POKEY. POKEY was a dedicated sound processor started by the core team and finished off by Doug Neubauer.
"The Atari 800's architecture evolved as an upgrade of the 2600. Conceived primarily by Steve Mayer, Joe Decuir and Jay Miner before I arrived at Atari, the original plan for the POKEY chip called for keyboard interface, audio and paddle controllers." xxxvi
- Doug Neubauer
The chip had four distinct sound channels, with the ability to set volume, frequency and waveform per channel. This gave Colleen and Candy sound production abilities far beyond the speaker beeps of most other personal computers at the time.
As the hardware was being finalized, Atari started working on the software required to get the computers up and running. After announcing late in 1978 that the new computer systems would be on display at the January CES in 1979, the scramble was on write software that would run the machines.
"Atari had been designing a personal computer for a couple years and had a group of programmers working on the OS for a long time. Atari then pre-announced that the computer would debut at the January 1979 CES. " xxxvii
- Alan Miller
To meet this date, Atari tapped some of the best programmers from the VCS team, Alan Miller, Larry Kaplan, Bob Whitehead, and David Crane to work on the operating system, while outsourcing the job of creating a version of the BASIC language for the computers.
"There is a period at Atari when there were no games coming from Larry Kaplan, Alan Miller, Bob Whitehead, and myself. As the most senior designers at Atari, we were tasked with creating the 800 operating system. This group, plus two others, wrote the entire operating system in about 8 months. A funny story from this time that Al Miller likes to tell has to do with the Atari BASIC cartridge that was to ship with the system. Atari had contracted with a young programmer named Bill Gates to modify a BASIC compiler that he had for another system to be used on the 800. After that project stalled for over a year Al was called upon to replace him with another developer. So, while Al is the only person I know ever to have fired Bill Gates, I suspect that rather than work on Atari BASIC, Gates was spending all his time on DOS for IBM. Probably not a bad career choice for him, do you think?" xxxviii
- David Crane
The BASIC language was finished by SMI corporation in time for CES, as was the internally developed OS.
"I'm very proud of the OS we created for the Atari 400/800. It was similar in complexity to QDOS -- the OS that Microsoft licensed a couple of years later from Seattle Computer Products and renamed MS-DOS for the IBM Personal Computers. However, the Atari OS was much better designed in terms of its user friendliness and it had a much, much richer graphics subsystem and many fewer bugs." xxxix
- Alan Miller