Editing Atari 2600

{{Infobox computer
| name         = Atari 2600
| image        = [[File:Atari-2600-Wood-4Sw-Set.jpg|250px]]
| caption      = Atari 2600 4-switch "woodgrain" model (1980-1982)
| manufacturer = Atari, Inc.
| type         = Home video game console
| release date = 11 September 1977 (as Video Computer System)<br>NA: September 1977<br>EU: 1978<br>JP: October 1983 (as Atari 2800)
| discontinued = 1 January 1992
| price        = US$199 (1977)
| cpu          = MOS Technology 6507 @ 1.19 MHz (NTSC) / 1.18 MHz (PAL)
| memory       = 128 bytes RAM (within 6532 RIOT)
| storage      = ROM cartridge (2 KB - 64 KB with bank switching)
| display      = 160 × 192 pixels (NTSC), 160 × 228 (PAL), 128 colors
| sound        = TIA custom chip, 2 channel mono
| dimensions   = 340 mm W × 240 mm D × 64 mm H (6-switch)
| weight       = 1.36 kg (Heavy Sixer), 1.14 kg (Light Sixer)
| os           = None
| predecessor  = Dedicated Pong consoles
| successor    = [[Atari 5200]]
| codename     = Stella
| model        = CX2600, CX2600A, 2600 Jr.
}}

The '''Atari 2600''', originally sold as the '''Atari Video Computer System''' (Atari VCS), is an 8-bit home video game console developed and manufactured by Atari, Inc. Released in September 1977, it popularized the use of ROM cartridges for game storage and established the modern video game console market. The system is built around the MOS Technology 6507 processor and the custom Television Interface Adaptor (TIA) chip, which handles graphics and sound generation without a frame buffer, requiring precise timing in software.

== System Architecture ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Sub-system !! Specification
|-
| '''CPU''' || MOS Technology 6507 @ 1.193182 MHz (NTSC) / 1.182298 MHz (PAL)<br>6502 variant with 13 address lines (8 KB address space)
|-
| '''Graphics/Sound''' || Television Interface Adaptor (TIA) CO10444 (NTSC) / CO11903 (PAL)<br>Generates video signal in real-time without frame buffer
|-
| '''RAM/I/O/Timer''' || MOS Technology 6532 RIOT<br>128 bytes RAM, two 8-bit I/O ports, programmable timer
|-
| '''Video''' || 160 × 192 pixels (NTSC), 160 × 228 (PAL)<br>128 colors (NTSC), 104 colors (PAL), 8 colors (SECAM)
|-
| '''Sprites''' || 2 players (8 pixels wide), 2 missiles (1 pixel), 1 ball (1 pixel)<br>All sprites can be stretched to 2×, 4×, or 8× width
|-
| '''Background''' || 40-pixel playfield (20-bit register, mirrored or repeated)
|-
| '''Audio''' || 2 independent channels, 4-bit volume, 5-bit frequency control<br>31 kHz max frequency, square wave and noise generation
|-
| '''ROM Space''' || 4 KB standard, up to 64 KB with bank switching
|}

== Memory Map ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+'''6507 Address Space'''
! Range !! Size !! Purpose
|-
| $0000-$007F || 128 bytes || TIA registers (write)
|-
| $0030-$003D || 14 bytes || TIA registers (read)
|-
| $0080-$00FF || 128 bytes || RIOT RAM (also mirrored at $0180-$01FF)
|-
| $0280-$0297 || 24 bytes || RIOT I/O and timer
|-
| $1000-$1FFF || 4 KB || Cartridge ROM (mirrored at $3000, $5000, $7000, $9000, $B000, $D000, $F000)
|}

== TIA Register Map ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Key TIA Registers'''
! Address !! Register !! Function
|-
| $00 || VSYNC || Vertical sync set-clear
|-
| $01 || VBLANK || Vertical blank set-clear
|-
| $02 || WSYNC || Wait for horizontal sync
|-
| $04-$05 || NUSIZ0-1 || Number-size player-missile 0-1
|-
| $06-$09 || COLUP0-1, COLUPF, COLUBK || Color registers
|-
| $0A || CTRLPF || Playfield control
|-
| $0D-$0F || PF0-2 || Playfield graphics
|-
| $10-$14 || RESP0-1, RESM0-1, RESBL || Reset sprite positions
|-
| $1B-$1D || GRP0-1 || Graphics player 0-1
|-
| $20-$24 || HMP0-1, HMM0-1, HMBL || Horizontal motion
|-
| $2A || HMOVE || Apply horizontal motion
|-
| $2C || CXCLR || Clear collision latches
|}

== Model Variants ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:90%; text-align:center;"
|+'''Production Models'''
! Model !! Years !! Description !! Key Features
|-
| '''Heavy Sixer''' || 1977-1978 || CX2600, thick plastic base || Sunnyvale manufacture, 6 front switches, channel selector
|-
| '''Light Sixer''' || 1978-1980 || CX2600, cost-reduced || Taiwan/Hong Kong manufacture, thinner case
|-
| '''4-Switch Woodgrain''' || 1980-1982 || CX2600A || Difficulty switches moved to rear, single PCB design
|-
| '''4-Switch Vader''' || 1982-1983 || CX2600A || All-black case, same internals as woodgrain
|-
| '''2600 Jr. (Short Rainbow)''' || 1984-1985 || Cost-reduced || Smaller form factor, rainbow stripe
|-
| '''2600 Jr. (Long Rainbow)''' || 1986-1991 || Final revision || Extended rainbow, slight PCB changes
|}

== Motherboard Revisions ==
Early 6-switch models used a two-board design with the main board housed in thick RF shielding and a separate switch board connected via ribbon cable. The 4-switch models consolidated to a single angled PCB. Key revisions include:
* '''Pre-Rev 14:''' CD4050 buffer IC for controller inputs (prone to static damage)
* '''Rev 14-15:''' Added static protection diodes, improved color output
* '''Jr. models:''' Fully integrated single board, cost-optimized design

== General Maintenance ==
{{Main|Atari 2600 General Maintenance}}

The Atari 2600 requires regular maintenance to ensure reliable operation after 40+ years. Common maintenance tasks include cleaning cartridge slots with isopropyl alcohol, treating oxidized switch contacts with DeoxIT, and ensuring proper ventilation to prevent overheating. The cartridge connector's 24 gold-plated contacts are prone to tarnishing and should be cleaned periodically. Power switches on 6-switch models frequently develop oxidation that can be resolved by working the switch repeatedly or applying contact cleaner through the switch opening.

== Troubleshooting Guide ==
{{Main|Atari 2600 Troubleshooting Guide}}

Common failures include blank screens caused by dirty cartridge contacts, power supply issues from failed 7805 voltage regulators, and static-damaged controller ports. The TIA chip is particularly sensitive to failure and typically requires replacement from a donor unit. No video output often indicates oxidized power switch contacts or failed electrolytic capacitors. Audio problems frequently stem from failed 820pF styrene capacitors (C206/C207 on 6-switch, C53/C54 on Jr.) which should be replaced with ceramic equivalents.

== Capacitor Replacement ==
{{Main|Atari 2600 Capacitor Replacement Guide}}

Critical capacitors requiring replacement on all models include the main 2200µF 16V filter capacitor and multiple 4.7µF bypass capacitors. The 6-switch models additionally require replacement of C103/C104 (0.22µF) near the voltage regulator to eliminate video artifacts. Styrene capacitors C206/C207 (6-switch) or C53/C54 (Jr.) commonly fail and cause audio loss. The 7805 voltage regulator should be upgraded from the original 0.5A rated part to a 1A version during any capacitor replacement.

== Power Supply ==
The console uses an external 9V DC power adapter (500mA minimum) with center-positive polarity. Internal regulation provides:
* '''+5V:''' Main logic supply (should measure 4.85-5.15V)
* '''Unregulated 9V:''' Direct to TIA for video generation

The 7805 voltage regulator mounted to the RF shield (6-switch) or heat sink (4-switch/Jr.) frequently fails after decades of operation. Symptoms include no power, intermittent operation, or voltage outside specifications.

== Controller Ports ==
The DE-9 controller ports support various peripherals:
* '''Standard joystick:''' 4 directions + 1 fire button
* '''Paddle controllers:''' Analog rotation via 1MΩ potentiometer
* '''Driving controller:''' Continuous rotation encoder
* '''Keyboard controllers:''' 12-key matrix (0-9, #, *)
* '''Track Ball:''' Digital pulses for X/Y movement

Port pinout is compatible with Commodore, Atari 8-bit computers, and Sega Master System (single button games only).

== Cartridge Slot ==
The 24-pin (2×12) edge connector accepts cartridges from 2 KB to 64 KB using various bank-switching schemes:
* '''Standard 2K/4K:''' Direct mapped, no switching
* '''F8 (8K):''' Atari standard, two 4K banks
* '''F6/F4 (16K):''' Four banks switched via $FFF6-$FFF9
* '''F0 (Megaboy):''' 64K with special switching

Cartridges contain mask ROM or EPROM chips, with some including additional RAM (Super Chip) or coprocessors (DPC, Pitfall II).

== Video Output ==
The TIA generates composite video internally, output through an RF modulator on channels 2 or 3 (selectable on some models). The video signal consists of:
* '''Horizontal:''' 228 color clocks per line (160 visible pixels)
* '''Vertical:''' 262 lines NTSC (192 visible), 312 lines PAL (228 visible)
* '''Frame rate:''' 59.92 Hz NTSC, 49.70 Hz PAL

Common video modifications include composite output (bypassing RF modulator) and S-Video separation for improved picture quality.

== Audio System ==
The TIA contains two independent audio channels, each with:
* '''Frequency divider:''' 5-bit (32 settings)
* '''Audio control:''' 4-bit waveform/noise selection
* '''Volume:''' 4-bit (16 levels)

Output is mixed to mono and routed through the RF modulator. Common modifications add stereo output by separating the two TIA audio channels.

== Common IC Identification ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Atari Part !! Standard Part !! Function
|-
| C010745 || MOS 6507 || CPU
|-
| C010750 || MOS 6532 || RIOT (RAM/IO/Timer)
|-
| C010444 || TIA (NTSC) || Television Interface Adaptor
|-
| C011903 || TIA (PAL) || Television Interface Adaptor
|-
| C012173A || CD4050 || Hex buffer (early models)
|}

== Technical Specifications Summary ==
* '''Clock Speed:''' 1.19 MHz (NTSC), 3.58 MHz pixel clock
* '''Instruction Timing:''' ~1.5 machine cycles per 160 pixels (racing the beam)
* '''Color Palette:''' 128 colors (16 hues × 8 luminance levels) NTSC
* '''Maximum Sprites:''' 5 hardware sprites, software multiplexed for more
* '''Playfield:''' 40 pixels wide, asymmetric or mirrored/repeated

== Service Information ==
Detailed schematics and service information are available in the Atari Field Service Manual. The system uses all through-hole components, making repairs feasible with basic soldering equipment. Common replacement parts include:
* '''7805 voltage regulator:''' Standard TO-220 package
* '''Power jack:''' 3.5mm × 1.3mm barrel connector
* '''RF modulator:''' UM1233 or compatible
* '''Controller ports:''' DE-9 female connectors

== Related Pages ==
* [[Atari 2600 General Maintenance]]
* [[Atari 2600 Troubleshooting Guide]]
* [[Atari 2600 Capacitor Replacement Guide]]
* [[Atari 5200]]
* [[Atari 7800]]

[[Category:Atari Systems]]