Atari 800XL

Atari 800XL
	Atari 800XL home computer
Specifications
Manufacturer	Atari, Inc.
Type	Home Computer
Released	1983
Discontinued	1985
Intro price	US$299 (1983)
CPU	MOS Technology 6502C @ 1.79 MHz (NTSC) / 1.77 MHz (PAL)
Memory	64 KB RAM, 16 KB ROM
Storage	External cassette tape, optional 5.25" floppy disk drive (Atari 1050)
Display	320×192 pixels (max), 40×24 text, 16 colours (ANTIC/GTIA)
Sound	POKEY: 4 voices, 8-bit mono
Dimensions	40.6 cm × 24.1 cm × 7.6 cm
Weight	2.1 kg
OS / Firmware	Atari BASIC (in ROM), Atari OS-B
Predecessor	Atari 800
Successor	Atari 65XE
Codename	Sweet-16
Model no.	800XL

The Atari 800XL is a home computer released by Atari, Inc. in 1983 as part of the Atari 8-bit family. It combined the improved electronics of the XL line with a revised, compact case and a full 64 KB of RAM, becoming one of the most popular Atari 8-bit models worldwide.

Architecture and Processor

The 800XL is powered by the MOS Technology 6502C microprocessor, running at:

1.79 MHz (NTSC systems)
1.77 MHz (PAL systems)

The CPU is supported by custom Atari chips:

ANTIC – programmable video interface, generating display lists and handling graphics modes.
GTIA – manages colour, player/missile graphics, and collision detection.
POKEY – provides sound, keyboard scanning, serial I/O, and random number generation.
PIA – handles parallel I/O for peripheral connections.

This architecture enabled advanced graphics and sound for its era, with hardware support for smooth scrolling, sprites (player/missile graphics), and multiple display modes.

Memory and Storage

The Atari 800XL features:

64 KB RAM – the maximum addressable by the 6502, allowing for more complex software and full compatibility with most Atari 8-bit programs.
16 KB ROM – containing the OS-B operating system and Atari BASIC (in most regions).

Storage options include:

Atari 1010 Program Recorder – cassette tape drive for data storage and loading.
Atari 1050 Floppy Disk Drive – external 5.25" disk drive for faster, more reliable storage.
Cartridge slot – for instant-loading software and utilities.

Display and Graphics

Graphics are handled by the ANTIC and GTIA chips, offering:

Resolution: up to 320×192 pixels (bitmap mode)
Text: 40 columns × 24 rows (default), with hardware support for 20, 40, or 80 columns (via software)
Colours: up to 16 on screen simultaneously, with a palette of 256 hues and 16 luminance levels
Player/Missile Graphics: 4 players (sprites) and 4 missiles, with collision detection and priority control
Smooth scrolling and fine control over display lists, enabling split-screen and mixed-mode graphics

These capabilities made the 800XL a favourite for games and graphics-intensive applications.

Sound Capabilities

Audio is generated by the POKEY chip, providing:

4 independent voices (channels), each with 8-bit resolution
Programmable frequency, volume, and distortion
White noise generation for percussion and effects
Keyboard scanning, serial I/O, and random number generation

The POKEY chip's flexibility allowed for a wide range of sound effects and music, contributing to the system's strong gaming library.

Input/Output and Expansion

The 800XL offers a comprehensive set of I/O ports:

Cartridge slot – for game and utility cartridges
SIO (Serial Input/Output) port – daisy-chained connection for disk drives, printers, modems, and other peripherals
Parallel Bus Interface (PBI) – a 50-pin edge connector for direct memory-mapped expansion (unique to XL models)
2 joystick ports – compatible with Atari-standard controllers
Composite and RF video outputs – for connection to TVs and monitors
Audio output – mono sound via TV or monitor
Power input – external power supply