[[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 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.
==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.
POKEY (POt KEYboard integrated circuit) is a digital Input/Output chip. It handles such disparate tasks as the SIO bus and its peripherals, audio generation, keyboard scan, and random number generation. It also digitizes the resistive paddle inputs and controls maskable interrupt (IRQ) requests from peripherals.