Editing Atari 2600 (section)

==Hardware==
{{Main|Atari 2600 hardware}}

The Atari 2600's CPU is the [[MOS Technology 6507]], a version of the [[MOS Technology 6502|6502]],<ref name="EGM62">{{cite magazine|date=September 1994|title=When Pac Ruled the Earth|page=18|magazine=[[Electronic Gaming Monthly]]|publisher=EGM Media, LLC|issue=62|url=https://archive.org/details/Electronic_Gaming_Monthly_62/page/n17/mode/2up}}</ref> running at 1.19 [[megahertz|MHz]] in the 2600.<ref>{{cite web | url = https://www.theguardian.com/technology/gallery/2017/feb/24/10-most-influential-games-consoles-in-pictures | title = 10 most influential games consoles – in pictures | first = Keith | last = Stewart | date = February 24, 2017 | access-date = September 17, 2018 | work = [[The Guardian]] | archive-date = September 17, 2018 | archive-url = https://web.archive.org/web/20180917215537/https://www.theguardian.com/technology/gallery/2017/feb/24/10-most-influential-games-consoles-in-pictures | url-status = live }}</ref> Though their internal silicon was identical, the 6507 was cheaper than the 6502 because its package included fewer [[Memory address|memory-address]] pins—13 instead of 16.{{sfn|Montfort|Bogost|2009|p=25}} The designers of the Atari 2600 selected an inexpensive cartridge interface<ref name="cartridge-socket">{{harvnb|Montfort|Bogost|2009|p=26}} The cartridge connector's 24 pins are allocated to one supply-voltage line, two ground lines, 8 data lines, and 13 address lines. The uppermost address line is used as a so-called [[chip select]] for the cartridge's ROM chip, however, leaving only 12 address lines for the chip's game program. Thus, without special "hardware tricks" built into the cartridge, an Atari 2600 game can occupy a maximum address space of 4 KB.</ref> that has one fewer address pins than the 13 allowed by the 6507, further reducing the already limited addressable memory from 8 KB (2<sup>13</sup> = 8,192) to 4 KB (2<sup>12</sup> = 4,096). This was believed to be sufficient as ''[[Combat (video game)|Combat]]'' was only 2 KB.{{sfn|Montfort|Bogost|2009|pp=25–26}} Later games circumvented this limitation with [[bank switching]].{{sfn|Montfort|Bogost|2009|p=88}}

The console has 128 [[byte]]s of [[random-access memory|RAM]] for scratch space, the [[call stack]], and the state of the game environment.

The top bezel of the console originally had six switches: power, TV type selection (color or black-and-white), game selection, left and right player difficulty, and game reset. The difficulty switches were moved to the back of the bezel in later versions of the console. The back bezel also included the controller ports, TV output, and power input.

===Graphics===
{{Main|Television Interface Adaptor}}
{{anchor|Racing the beam}}
[[File:A2600 Pitfall.png|thumb|''[[Pitfall!]]'' (1982) has more advanced graphics than the games the VCS launched with. The black bar on the left provides extra time for the program to prepare graphics between each scanline.<ref name=":0" />]]

The Atari 2600 was designed to be compatible with the [[cathode-ray tube]] television sets produced in the late 1970s and early 1980s, which commonly lack auxiliary video inputs to receive audio and video from another device. Therefore, to connect to a TV, the console generates a [[radio frequency]] signal compatible with the regional television standards ([[NTSC]], [[PAL]], or [[SECAM]]), using a special switch box to act as the television's antenna.<ref>{{cite journal |last1=Arceneaux |first1=Noah |title=Review Article: Game theories, technologies and techniques of play |journal=New Media & Society |date=19 February 2010 |volume=12 |issue=1 |pages=161–166 |doi=10.1177/1461444809350996|s2cid=220595570 }}</ref><ref name="ieee decuir"/>

Atari developed the [[Television Interface Adaptor]] (TIA) chip in the VCS to handle the graphics and conversion to a television signal. It provides a single-color, 20-bit background register that covers the left half of the screen (each bit represents 4 adjacent pixels) and is either repeated or reflected on the right side. There are 5 single-color [[Sprite (computer graphics)|sprites]]: two 8-pixel wide ''players''; two 1 bit ''missiles'', which share the same colors as the players; and a 1-pixel ''ball'', which shares the background color. The 1-bit sprites all can be controlled to stretch to 1, 2, 4, or 8 pixels.<ref name="Wright">{{citation|last=Wright|first=Steve|title=Stella Programmer's Guide|date=1979-12-03}}</ref>

The system was designed without a [[frame buffer]] to avoid the cost of the associated [[Random-access memory|RAM]]. The background and [[Sprite (computer graphics)|sprites]] apply to a single [[scan line]], and as the display is output to the television, the program can change colors, sprite positions, and background settings. The careful timing required to sync the code to the screen on the part of the programmer was labeled "[[racing the beam]]"; the actual game logic runs when the television beam is outside of the visible area of the screen.{{sfn|Montfort|Bogost|2009}}<ref name="Wired racing"/> Early games for the system use the same visuals for pairs of scan lines, giving a lower vertical resolution, to allow more time for the next row of graphics to be prepared. Later games, such as ''Pitfall!'', change the visuals for each scan line or extend the black areas around the screen to extend the game code's processing time.<ref name="gi activision start" /><ref name=":0">{{Cite magazine|url=https://www.wired.com/2009/03/racing-the-beam/|title=Racing the Beam: How Atari 2600's Crazy Hardware Changed Game Design|last=Kohler|first=Chris|date=March 13, 2009|magazine=[[Wired (magazine)|Wired]]|archive-url=https://web.archive.org/web/20140712094639/https://www.wired.com/2009/03/racing-the-beam/|archive-date=July 12, 2014|url-status=live}}</ref>

Regional releases of the Atari 2600 use modified [[Television Interface Adaptor|TIA]] chips for each region's television formats, which require games to be developed and published separately for each region. All modes are 160 pixels wide. [[NTSC]] mode provides 192 visible lines per screen, drawn at 60&nbsp;[[Hertz|Hz]], with 16 colors, each at 8 levels of brightness. [[PAL]] mode provides more vertical scanlines, with 228 visible lines per screen, but drawn at 50&nbsp;Hz and only 13 colors. [[SECAM]] mode, also a 50&nbsp;[[Hertz|Hz]] format, is limited to 8 colors, each with only a single brightness level.<ref name="Wright"/><ref name="TIA color chart">Atari 2600 [http://www.biglist.com/lists/stella/archives/200109/msg00285.html "TIA color chart"] {{webarchive |url=https://web.archive.org/web/20110707234118/http://www.biglist.com/lists/stella/archives/200109/msg00285.html |date=July 7, 2011 }}</ref>

===Controllers===
{{multiple image
 | total_width = 320
 | image1      = Atari-2600-Paddle-Controller-FR.jpg 
 | caption1    = CX30 paddle
 | image2      = Atari-2600-Joystick.jpg
 | caption2    = CX40 joystick
}}

The first VCS bundle has two types of controllers: a joystick (part number CX10) and pair of rotary [[paddle (game controller)|paddle controllers]] (CX30). Driving controllers, which are similar to paddle controllers but can be continuously rotated, shipped with the ''[[Indy 500 (1977 video game)|Indy 500]]'' launch game. After less than a year, the CX10 joystick was replaced with the CX40 model<ref name="current"/> designed by James C. Asher.<ref>{{cite web|title=United States Patent 4,349,708|url=https://patentimages.storage.googleapis.com/pdfs/1ae0e2937613724a0e9f/US4349708.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://patentimages.storage.googleapis.com/pdfs/1ae0e2937613724a0e9f/US4349708.pdf |archive-date=2022-10-09 |url-status=live|date=September 14, 1982}}</ref> Because the [[Atari joystick port]] and [[Atari CX40 joystick|CX40 joystick]] became industry standards, 2600 joysticks and some other peripherals work with later systems, including the [[MSX]], [[Commodore 64]], [[Amiga]], [[Atari 8-bit computers]], and [[Atari ST]]. The CX40 joystick can be used with the [[Master System]] and [[Sega Genesis]], but does not provide all the buttons of a native controller. Third-party controllers include Wico's Command Control joystick.<ref>{{cite web|last=Hruschak|first=PJ|date=April 1, 2008|title=Gamertell Review: Wico's Command Control Joystick|url=http://www.technologytell.com/gaming/31885/gamertell-review-wicos-command-control-joystick/|url-status=dead|archive-url=https://web.archive.org/web/20160403210511/http://www.technologytell.com/gaming/31885/gamertell-review-wicos-command-control-joystick/|archive-date=April 3, 2016|website=Technologytell.com}}</ref> Later, the CX42 Remote Control Joysticks, similar in appearance but using wireless technology, were released, together with a receiver whose wires could be inserted in the controller jacks.<ref>{{Cite web|url=https://atariage.com/controller_page.php?SystemID=2600&ControllerID=27|title=AtariAge – Atari 2600 – Controllers – Remote Control Joysticks|website=atariage.com|access-date=2019-02-18|archive-date=October 11, 2017|archive-url=https://web.archive.org/web/20171011122525/http://atariage.com/controller_page.php?SystemID=2600&ControllerID=27|url-status=live}}</ref>

Atari introduced the CX50 Keyboard Controller in June 1978 along with two games that require it: ''Codebreaker'' and ''Hunt & Score''.<ref name="current"/> The similar, but simpler, CX23 Kid's Controller was released later for a series of games aimed at a younger audience.<ref>{{Cite web|url=https://atariage.com/controller_page.php?SystemID=2600&ControllerID=6|title=AtariAge – Atari 2600 – Controllers – Kid's Controller|website=atariage.com|access-date=2019-02-18|archive-date=May 18, 2019|archive-url=https://web.archive.org/web/20190518115901/https://atariage.com/controller_page.php?SystemID=2600&ControllerID=6|url-status=live}}</ref> The CX22 Trak-Ball controller was announced in January 1983 and is compatible with the Atari 8-bit computers.<ref>{{cite web|last1=Current|first1=Michael D.|title=Atari 8-Bit Computers FAQ|url=http://www.faqs.org/faqs/atari-8-bit/faq/section-102.html|access-date=May 24, 2018|archive-date=August 28, 2018|archive-url=https://web.archive.org/web/20180828161141/http://www.faqs.org/faqs/atari-8-bit/faq/section-102.html|url-status=live}}</ref>

There were two attempts to turn the Atari 2600 into a keyboard-equipped [[home computer]]: Atari's never-released CX3000 "Graduate" keyboard,<ref>{{cite web |title=The Atari "Graduate" Computer CX-3000 |url=http://www.atarimuseum.com/videogames/consoles/2600/a3000.html |website=Atari Museum |access-date=April 22, 2019 |archive-date=April 30, 2015 |archive-url=https://archive.today/20150430005623/http://www.atarimuseum.com/videogames/consoles/2600/a3000.html |url-status=live }}</ref> and the [[CompuMate]] keyboard by [[Spectravideo]] which was released in 1983.<ref>{{cite web |title=The Spectravideo "Compumate" Keyboard |url=http://www.atarimuseum.com/videogames/consoles/2600/compumat.html |website=Atari Museum |access-date=June 23, 2019 |archive-date=November 26, 2019 |archive-url=https://web.archive.org/web/20191126222146/http://www.atarimuseum.com/videogames/consoles/2600/compumat.html |url-status=live }}</ref>