[[File:Atari XE Games System-gen1.jpeg|thumb|right|Atari XEGS]]
The [[Atari 8-bit]] computer series, launched in 1979 as the Atari Home Computer System, included the Atari 400 and 800. Powered by the 8-bit MOS Technology [[6502 ]] CPU and custom coprocessors, these computers offered advanced graphics and sound for their time.
The Atari 800 was the high-end model, while the 400 was a budget-friendly option with a membrane keyboard and 8 KB of RAM. Both supported plug-and-play peripherals via the Atari SIO serial (Serial I/O) bus, a precursor to USB technology. The architecture was later used in the 1982 Atari 5200 console, though the systems were not software-compatible.
Newer models followed, beginning with the short-lived 1200XL in 1983, replaced by the 600XL and 800XL. After Atari Corporation took over, the 65XE and 130XE were released in 1985, featuring a lighter design, two joystick ports, and built-in Atari BASIC. The 130XE had 128 KB of RAM.
==Hardware==
The 400/800 originally used the standard 6502B CPU. Later 400/800 CPU board was released that boards used the SALLY 6502C (the C is for custom, not CMOS) chip. The SALLY chip equipped all new Atari 400 & 800, and their successors.
In addition to its 1POKEY (POt KEYboard integrated circuit) is a digital Input/Output chip.79 Mhz [[MOS 6502|6502]] CPU, It handles such disparate tasks as the Atari computer offloads some of the work to SIO bus and its specialized chips: ANTICperipherals, CTIA & POKEYaudio generation, keyboard scan, and random number generation. It also digitizes the resistive paddle inputs and controls maskable interrupt (IRQ) requests from peripherals.
ANTIC and CTIA together produce the graphics, up to a resolution of 320x192 pixels, sprites, scrolling in any direction, different graphic modes that can be mixed on the same screen, etc.
When launched in the US, the Atari 400 & 800 came with a CTIA (Color Television Interface Adapter) chip, which offered 9 graphic and text modes (GR.0-8) in Atari BASIC and a 128-colour palette. In early 1982, CTIA was replaced by GTIA (Graphic Television Interface Adapter), which provided 3 additional graphics modes (GR.9-10-11) in Atari BASIC, with a 256-colour palette. The GTIA chip equipped all new Atari 400 & 800, and their successors.
POKEY {| class="wikitable"! Parameter !! PAL Atari 8-bit !! NTSC Atari 8-bit|-| Master Clock Frequency || 17.734475 MHz || 14.31818 MHz|-| Clock Divider|| 10 || 8|-| CPU Clock Speed || 1,773,447 Hz || 1,789,772 Hz|-| Raster Lines per Frame || 312 || 262|-| CPU Cycles per Line || 114 || 114|-| Total CPU Cycles per Frame || 35,568 || 29,868|-| Calculated Frame Rate || ~49.86 Hz <br /><small>(POt KEYboard integrated circuit1,773,447 / 35,568) is a digital Input</Output chipsmall> || ~59. It handles such disparate tasks as the serial I92 Hz <br /O ><small>(SIO) bus and its peripherals1, audio generation789, keyboard scan772 / 29, and random number generation. It also digitizes the resistive paddle inputs and controls maskable interrupt (IRQ868) requests from peripherals.</small>|}
==Links==
*[https://youtu.be/57CNQ7xp69o Over 50 Atari 400/800 games in under 30 minutes] [https://youtu.be/06oF6gGybZI 1000 Atari 8-bit games]
*[https://youtu.be/WDAZAgrzNoo How Atari 8-Bit Computers Work!] by [[The 8-Bit Guy]]
* [https://www.atariarchives.org/dere/ De Re Atari] [https://www.musanim.com/mam/DeReAtari.pdf PDF version]
* [[media:Atari 400-800 Service Manual.pdf|Atari 400-800 Service Manual]]
* [[media:Pokey datasheet.pdf|POKEY]] [[media:GTIA datasheet.pdf|GTIA]] [[media:ANTIC datasheet.pdf|ANTIC]] Datasheets