Editing Enhanced Graphics Adapter

{{Short description|IBM PC graphic adapter and display standard}}
{{Infobox GPU
| name         = Enhanced Graphics Adapter
| image        =IBM EGA card.jpg 
| codename     = 
| created      = {{Start date and age|October 1984}}<ref>{{cite web | url=http://www-01.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_ca/4/897/ENUS184-114/index.html | title=IBM Enhanced Graphics Adapter, IBM Graphics Memory Expansion Card, and IBM Graphics Memory Module | date=10 September 1984 }}</ref>
| transistors  = 
| architecture = [[Motorola 6845]]; [[Chips and Technologies]] 82C431, 82C432, 82C433, 82C434
| entry        = IBM EGA card, [[Chips and Technologies]], [[ATI Wonder series#EGA Cards|ATI EGA Wonder]]
| midrange     = [[ATI Wonder series#EGA Cards|ATI EGA Wonder 800]]
| highend      = [[ATI Wonder series#EGA Cards|ATI EGA Wonder 800+]]
| enthusiast   = 
| d3dversion   = 
| predecessor  = [[IBM Monochrome Display Adapter|Monochrome Display Adapter]], [[Color Graphics Adapter]]
| successor    = [[IBM 8514]], [[Video Graphics Array]]
|caption=Original 64&nbsp;KB IBM EGA card}}

The '''Enhanced Graphics Adapter''' ('''EGA''') is an [[IBM PC compatible|IBM PC]] [[Video card|graphics adapter]]<ref name=":4" /><ref name=":5" />  and ''de facto'' [[computer display standard]] from 1984 that superseded the [[Color Graphics Adapter|CGA]] standard introduced with the [[IBM Personal Computer|original IBM PC]], and was itself superseded by the [[Video Graphics Array|VGA]] standard in 1987. In addition to the original EGA card manufactured by [[IBM]], many compatible third-party cards were manufactured, and EGA graphics modes continued to be supported by VGA and later standards.

== History ==
EGA was introduced in October 1984 by IBM,<ref name=":4">High-Resolution Standard Is Latest Step in DOS Graphics Evolution, ''InfoWorld'', June 26, 1989, p. 48.</ref><ref name=":5">News Briefs, Big Blue Turns Colors, ''InfoWorld'', October 8, 1984.</ref> shortly after its new [[IBM Personal Computer AT|PC/AT]]. The EGA could be installed in previously released IBM PCs, but required a [[Read-only memory|ROM]] upgrade on the [[Motherboard|mainboard]].<ref>{{Cite book |url=https://ibm.retropc.se/ibm_ega/IBM%20EGA%20-%20Installation%20Instructions.pdf |title=IBM EGA Installation Instructions |year=1984 |pages=1 |access-date=2020-08-15 |archive-date=2022-02-11 |archive-url=https://web.archive.org/web/20220211184437/https://ibm.retropc.se/ibm_ega/IBM%20EGA%20-%20Installation%20Instructions.pdf |url-status=dead }}</ref>

[[Chips and Technologies]]' first product, announced in September 1985, was a four-chip EGA [[chipset]] that handled the functions of 19 of IBM's proprietary chips on the original Enhanced Graphics Adapter. By that November's [[COMDEX]], more than a half dozen companies had announced EGA-compatible boards based on C&T's chipset.<ref name="EGS">[https://books.google.com/books?id=a91QXlvTPHAC&pg=PA140 The Enhanced Graphics Standard Comes of Age], ''[[PC Magazine]]'', August 1986.</ref> The first EGA-compatible board was Vega in December 1985, released by [[Video Seven]] and using C&T's chipset.<ref name=ega>{{cite journal | last=Bermant | first=Charles | date=February 11, 1986 | url=https://books.google.com/books?id=yCeTeDMBhg8C&pg=PA34 | title=EGA Standard Evolves for PC Graphics Users | work=PC Magazine | publisher=Ziff-Davis | volume=5 | issue=3 | pages=33–34 | via=Google Books | access-date=February 20, 2024 | archive-date=February 20, 2024 | archive-url=https://web.archive.org/web/20240220094029/https://books.google.com/books?id=yCeTeDMBhg8C&pg=PA34 | url-status=live }}</ref>{{rp|34}} The Vega was half the length of the original IBM EGA board.<ref name=race>{{cite journal | last=Clark | first=Don | date=April 23, 1987 | url=https://www.proquest.com/docview/302120522/ | title=IBM Signals a New Race for Video-7 | work=The San Francisco Chronicle | page=33 | via=ProQuest}}</ref>

Between 1984 and 1987, several third-party manufacturers produced [[Computer compatibility|compatible]] cards, such as the ''Autoswitch EGA''<ref name=":0">{{Cite news |last=Kallenbach |first=Rolf |date=July 28, 1986 |title=Paradise EGA Makes Switching Automatic |pages=53 |work=InfoWorld |url=https://books.google.com/books?id=Vy8EAAAAMBAJ&q=infoworld+enhanced+%22EGA%22&pg=PA53}}</ref> or [[Genoa Systems]]' ''Super EGA'' chipset.<ref>{{Cite news |last=Brownstein |first=Mark |date=February 23, 1987 |title=Genoa Systems Ready to Ship $449 Half-Size Graphics Card |pages=16 |work=InfoWorld |url=https://books.google.com/books?id=1DAEAAAAMBAJ&q=Genoa+Systems+Ready+to+Ship+%24449+Half-Size+Graphics+Card%2C+InfoWorld%2C+February+23%2C+1987&pg=PA16}}</ref> Later cards supporting an extended version of the VGA were similarly named [[Super VGA]].

The EGA standard was made obsolete in 1987 by the introduction of [[Multi-Color Graphics Array|MCGA]] and VGA with the [[IBM PS/2|PS/2]] computer line.<ref>Scott Mueller, ''Upgrading and Repairing PCs, Tenth Edition'', Que, 1998, 0-7897-1636-4, page 515.</ref>

== Adoption ==
By 1985 ''[[InfoWorld]]'' described EGA as the "next graphics standard", but with "sluggish sales" because of high cost and lack of software support. The magazine said that "market reaction ... although positive, has not been overwhelming, in part because the EGA's complexity has slowed software vendors' efforts to support it".{{r|petrosky19850819}} Commercial software began supporting EGA soon after its introduction, with ''[[The Ancient Art of War]],'' released in 1984.<ref>{{Cite web |title=The Ancient Art of War for DOS (1984) |url=https://www.mobygames.com/game/dos/ancient-art-of-war |access-date=2022-12-10 |website=MobyGames}}</ref>  ''[[Microsoft Flight Simulator 2.0|Microsoft Flight Simulator v2.12]],<ref name="auto1">{{Cite web |title=Microsoft Flight Simulator (v2.0) for PC Booter (1984) |url=https://www.mobygames.com/game/microsoft-flight-simulator-v20 |website=MobyGames}}</ref><ref>{{Cite news |last=Dudek |first=Virginia |date=July 23, 1985 |title=PC Update |pages=53 |work=PC Magazine |url=https://books.google.com/books?id=Dwvc24nC0IQC&dq=%22%22Microsoft+Flight+Simulator+3%22&pg=PA53}}</ref>'' ''Jet'',<ref>{{Cite web |title=Jet for DOS (1985) |url=https://www.mobygames.com/game/dos/jet |access-date=2022-12-10 |website=MobyGames}}</ref> [[Silent Service (video game)|''Silent Service'']],<ref>{{Cite web |title=Silent Service for DOS (1985) |url=https://www.mobygames.com/game/dos/silent-service |access-date=2022-12-10 |website=MobyGames}}</ref> and ''Cyrus'',<ref>{{Cite web |title=Cyrus for DOS (1985) |url=https://www.mobygames.com/game/dos/cyrus |access-date=2022-12-10 |website=MobyGames}}</ref> all released in 1985, offered EGA support, along with [[Windows 1.0x|Windows 1.0]]. Sierra's ''[[King's Quest III]]'', released in 1986, was one of the earliest mainstream [[PC game]]s to use it.

The first clone boards appeared in late 1985, lowering EGA's cost.<ref name="petrosky19850819">{{Cite magazine |last=Petrosky |first=Mary |date=1985-08-19 |title=Market Looks to EGA as De Facto Standard |url=https://books.google.com/books?id=_S4EAAAAMBAJ&lpg=PA23&dq=MacBasic&pg=PA32#v=onepage&f=true |access-date=2025-01-09 |magazine=InfoWorld |publisher=InfoWorld Media Group, Inc. |pages=32-36 |language=en}}</ref> By 1987, EGA support was commonplace.<ref>{{Cite news |last=Hummel |first=Robert |date=June 23, 1987 |title=Get the full EGA color spectrum |pages=311 |work=PC Magazine |url=https://books.google.com/books?id=sgKP4GXb1AQC&q=EGA+popularity&pg=PA311}}</ref> Most software made up to 1991 could run in EGA, although the vast majority of commercial games used {{resx|320×200}} with 16 colors for backward compatibility with CGA and [[Tandy Graphics Adapter|Tandy]], and to support users who did not own an enhanced EGA monitor. 350-line modes were mostly used by freeware/shareware games and application software, although ''[[SimCity (1989 video game)|SimCity]]'' is a notable example of a commercial game that runs in {{resx|640×350}} with 16 colors mode.<ref>{{Cite web |last=Edwards |first=Benj |date=2019-06-10 |title=EGA Turns 35: 10 Iconic EGA Games of Yesteryear |url=https://au.pcmag.com/gallery/62407/ega-turns-35-10-iconic-ega-games-of-yesteryear |access-date=2022-12-09 |website=PCMag Australia |language=en-au}}</ref><ref>{{Citation |last=Maxis |title=SimCity Graphics - Graphics Set 1 Ancient Cities (IBM-PC) - Box, Manual, Disk Scans (1200DPI) |date=1990 |url=http://archive.org/details/sim-city-graphics-graphics-set-1-ancient-cities-ibmpchiresscans |access-date=2022-12-09}}</ref> Modern adventure games, like ''[[The Crimson Diamond]]'', use freeware tools like the [[Adventure Game Studio]] to create games with EGA-style color palettes but with modern features.<ref name=":32">{{Cite web |last=Extension |first=Time |date=2024-06-21 |title="I Have No Interest In 3D Games" - Meet The Devs Keeping EGA Alive In The Modern Day |url=https://www.timeextension.com/features/i-have-no-interest-in-3d-games-meet-the-devs-keeping-ega-alive-in-the-modern-day |access-date=2024-08-19 |website=Time Extension |language=en-GB}}</ref>

== Hardware design ==
[[File:IBM_5151,_5153,_5154_monitors.jpg|alt=|thumb|IBM MDA, CGA and EGA monitors, all supported by the EGA card]]
The original IBM EGA was an 8-bit PC [[Industry Standard Architecture|ISA]] card with 64&nbsp;KB of onboard [[Random-access memory|RAM]]. An optional [[Expansion card|daughter-board]] (the ''Graphics Memory Expansion Card'') provided a minimum of 64&nbsp;KB additional RAM, and up to 192 KB if fully populated with the ''Graphics Memory Module Kit''.<ref>{{Cite book |url=https://ibm.retropc.se/ibm_ega/IBM%20EGA%20-%20Installation%20Instructions.pdf |title=IBM EGA Installation Instructions |pages=9, 10, 11 |access-date=2020-08-15 |archive-date=2022-02-11 |archive-url=https://web.archive.org/web/20220211184437/https://ibm.retropc.se/ibm_ega/IBM%20EGA%20-%20Installation%20Instructions.pdf |url-status=dead }}</ref> Without these upgrades, the card would be limited to four colors in 640&nbsp;×&nbsp;350 mode.<ref>{{Cite book |url=http://minuszerodegrees.net/oa/OA%20-%20IBM%20Enhanced%20Graphics%20Adapter.pdf |title=IBM Enhanced Graphics Adapter manual |pages=7}}</ref>

Output was via direct-drive [[RGB color model|RGB]],<ref>{{Cite book|url=http://minuszerodegrees.net/oa/OA%20-%20IBM%20Enhanced%20Graphics%20Adapter.pdf |title=IBM Enhanced Graphics Adapter manual |pages=83}}</ref> as with the CGA, but no [[composite video]] output was included.<ref>{{cite journal |last=Hart |first=Glenn A. |date=December 25, 1984 |title=IBM Sets a New Standard |url=https://books.google.com/books?id=azbgSlPdJawC&pg=PA173 |journal=PC Magazine |publisher=Ziff-Davis Publishing |volume=3 |issue=25 |page=173}}</ref> MDA and CGA monitors could be driven, as well as newly released enhanced color monitors for use specifically with EGA.<ref name=":3">{{Cite book |url=http://minuszerodegrees.net/oa/OA%20-%20IBM%20Enhanced%20Graphics%20Adapter.pdf |title=IBM Enhanced Graphics Adapter manual |pages=5, 6, 7}}</ref>

EGA-specific monitors used a [[Dual-sync monitor|dual-sync]] design which could switch from the 15.7&nbsp;kHz of 200-line modes to 21.8&nbsp;kHz for 350-line modes.<ref name=":3" />[[File:KL Genoa EGA.jpg|thumb|A non-IBM EGA card]]

Many EGA cards have [[DIP switch]]es on the back of the card to select the monitor type. If CGA is selected, the card will operate in 200-line mode and use 8×8 characters in [[text mode]]. If EGA is selected, the card will operate in 350-line mode and use 8×14 text.

Some third-party cards using the EGA specification were sold with the full 128&nbsp;KB of RAM from the factory, while others included as much as 256&nbsp;KB to enable multiple graphics pages, multiple text-mode [[Character encoding|character sets]], and large [[scrolling]] displays.<ref name=":0" /> A few third-party cards, such as the [[ATI Technologies]] [[EGA Wonder]], built on the EGA standard to additionally offer features such as extended graphics modes as high as {{resx|800×560}} and automatic monitor type detection.<ref>{{Cite news |date=August 17, 1987 |title=EGA Wonder Any Software. Any Monitor. Any Time. 800x560 640x480 |pages=41 |work=InfoWorld |url=https://books.google.com/books?id=2jsEAAAAMBAJ&q=infoworld+ATI+EGA+400+line&pg=PA41}}</ref>

== Capabilities ==
[[File:Ega 320x200x16 ratio.png|thumb|EGA {{resx|320×200}}&nbsp;×&nbsp;16 colors, CGA-compatible palette]]
[[File:Ega 640x200x16 aspect ratio.png|thumb|EGA {{resx|640×200}}&nbsp;×&nbsp;16 colors, CGA-compatible  palette]]
[[File:Birds ega.png|thumb|EGA {{resx|640×350}}&nbsp;×&nbsp;16 colors, EGA palette]]
[[File:Arachne EGA Mode.png|thumb|Screenshot of the [[Arachne (web browser)|Arachne]] web browser using the {{resx|640×350}} graphics mode. The screenshot contains 14 colors.]] 
[[File:VGA text sample animation.gif|thumb|Sample of [[text mode]] characters with cursor]]
EGA produces a display of up to 16 colors (using a fixed [[Palette (computing)|palette]], or one selected from a [[List of monochrome and RGB color formats#6-bit RGB|gamut of 64 colors (6-bit RGB)]], depending on mode) at several resolutions up to 640&nbsp;×&nbsp;350  pixels, as well as two monochrome modes at higher resolutions. EGA cards include a ROM to extend the system [[BIOS]] for additional graphics functions, and a custom [[Video display controller|CRT controller (CRTC)]].<ref name=":1" />

The IBM EGA CRTC supports all of the modes of the IBM [[IBM Monochrome Display Adapter|MDA]] and CGA adapters through specific mode options,<ref name=":1">{{Cite book |url=http://minuszerodegrees.net/oa/OA%20-%20IBM%20Enhanced%20Graphics%20Adapter.pdf |title=IBM Enhanced Graphics Adapter manual |pages=1, 81}}</ref> but it is not fully register-compatible with the [[Motorola]] [[MC6845]] used in those cards, so software that directly programs the registers to select modes may produce different results on the EGA.<ref>{{Cite book| url=http://minuszerodegrees.net/oa/OA%20-%20IBM%20Enhanced%20Graphics%20Adapter.pdf |title=IBM Enhanced Graphics Adapter manual |pages=75}}</ref>

Supported resolutions are 320&nbsp;×&nbsp;200 and 640&nbsp;×&nbsp;200 (on a CGA or EGA monitor<ref name=":2">{{Cite book |url=http://minuszerodegrees.net/oa/OA%20-%20IBM%20Enhanced%20Graphics%20Adapter.pdf |title=IBM Enhanced Graphics Adapter manual |pages=5, 6, 7}}</ref>), 720&nbsp;×&nbsp;350  and 640&nbsp;×&nbsp;350 (on an MDA monitor) and 320&nbsp;×&nbsp;350 and 640&nbsp;×&nbsp;350 (on an EGA monitor). EGA scans at 21.8&nbsp;kHz when 350-line modes are used and 15.7&nbsp;kHz when 200-line modes are used. For both horizontal scan rates, the vertical scan rate is 60 Hz.<ref name=":3" />

In the 640&nbsp;×&nbsp;350 high-resolution mode, which requires an enhanced EGA monitor, 16 colors can be selected from a palette of 64, comprising all combinations of two bits per pixel (four levels of intensity) for red, green and blue. On EGA adapters with only 64&nbsp;KB of video RAM, only 4 colors can be selected per pixel.<ref name=":3" /> The 640&nbsp;×&nbsp;200 and 320&nbsp;×&nbsp;200 graphics modes provide backward compatibility with CGA software and monitors, but they can use the entire 16-color [[Color Graphics Adapter#Color palette|CGA palette]] simultaneously, instead of the smaller 4-color palettes that CGA is limited to in those modes.<ref name=":2" />

EGA's 16-color [[All points addressable|graphic modes]] use [[bit plane]]s and [[bit mask|mask]] [[hardware register|registers]]<ref>[http://support.microsoft.com/KB/45699 Complete Instructions to BLOAD and BSAVE EGA and VGA Screens], [[Microsoft]].</ref> together with CPU [[bitwise operation]]s<ref>{{cite book |title=Graphics Programming Black Book |last=Abrash |first=Michael |author-link=Michael Abrash |year=2001 |publisher=[[Penguin Group|Coriolis Group Books]] |isbn=1-57610-174-6 |pages=[https://archive.org/details/michaelabrashsgr00abra/page/1342 1342] |url=https://archive.org/details/michaelabrashsgr00abra/page/1342 |chapter=Chapter 43: Bit-plane animation |chapter-url=http://www.phatcode.net/res/224/files/html/ch43/43-01.html |access-date=February 6, 2017 |url-access=registration }}</ref> for [[graphics accelerator|accelerated graphics]]. The same techniques went on to be used in the [[Video Graphics Array|VGA]].

=== Modes ===
EGA supports:
* {{resx|640×350}}&nbsp;×&nbsp;16 colors (from a 6&nbsp;bit palette of 64 colors), pixel [[aspect ratio]] of 1:1.37.
* {{resx|640×350}}&nbsp;×&nbsp;2 colors, pixel aspect ratio of 1:1.37.
* {{resx|640×200}}&nbsp;×&nbsp;16 colors, pixel aspect ratio of 1:2.4.
* {{resx|320×200}}&nbsp;×&nbsp;16 colors, pixel aspect ratio of 1:1.2.

Text modes:
* {{resx|40x25}} with {{resx|8x8}} pixel font (effective resolution of {{resx|320×200}})
* {{resx|80x25}} with {{resx|8x8}} pixel font (effective resolution of {{resx|640×200}})
* {{resx|80x25}} with {{resx|8x14}} pixel font (effective resolution of {{resx|640×350}})
* {{resx|80x43}} with {{resx|8x8}} pixel font (effective resolution of {{resx|640×344}})

Extended graphics modes of third-party boards:{{cn|date=January 2024}}
* {{resx|640×400}}
* {{resx|640×480}}
* {{resx|720×540}}
* {{resx|800×560}}

=== Color palette ===
With the EGA, all [[List of 16-bit computer hardware palettes#EGA|16 CGA colors]] can be used simultaneously, and each can be mapped in from a larger palette of 64 colors (two bits each for red, green and blue). The [[Color Graphics Adapter#With an RGBI monitor|CGA's alternate brown]] color is included in the larger palette, so it can be used without any additional display hardware. The later VGA standard built on this by mapping each of the 64 colors in from a larger, customizable, palette of 256.

Standard EGA monitors do not support use of the extended color palette in 200-line modes, because the monitor cannot distinguish between being connected to a CGA card or being connected to an EGA card outputting a 200-line mode. EGA redefines some pins of the connector to carry the extended color information. If the monitor were connected to a CGA card, these pins would not carry valid color information, and the screen might be garbled if the monitor were to interpret them as such. For this reason, standard EGA monitors will use the CGA pin assignment in 200-line modes, so the monitor can also be used with a CGA card.{{Citation needed|date=August 2020}}

Some EGA monitors are ''switchable'', meaning that they can be set up to use the full palette even in 200-line modes, often through a mechanical switch. Only a few commercial games were released with support for the extended color palette in {{resx|320×200}} or {{resx|640×200}} (including the DOS version of ''[[Super Off Road]]'').<ref>{{Cite web |last=swarmik |date=November 2018 |title=EGA 64-color 320x200 mode on switchable monitors |url=https://swarmik.tumblr.com/post/179660020524/ega-64-color-320x200-mode-on-switchable-monitors |access-date=2022-12-09 |website=Tumblr}}</ref><ref>{{Cite web |last=RetroArchivesFr |date=2018-12-16 |title=Ivan "Ironman" Stewart's Super Off Road |url=https://retroarchives.fr/ivan-ironman-stewarts-super-off-road/ |access-date=2022-12-09 |website=Retro Archives |language=fr-FR}}</ref>

When selecting a color from the EGA palette, two bits are used for the red, green and blue channels to signal values of 0, 1, 2 or 3. For instance, to select the color magenta, the red and blue values would be medium intensity (2, or 10 in binary) and the green value would be off (0).

The table below displays an example palette matching the standard 16 CGA colors, with their representations in rgbRGB binary (internal card bit order), where the lowercase letters are the low-intensity bits, and uppercase letters are high-intensity bits. Decimal and hexadecimal values (converted to equivalent [[Color depth#True color (24-bit)|24-bit]] [[sRGB]] [[web colors]]) are also shown.

[[File:Screen color test EGA 16colors CGA.png|thumb|Screen color test with standard 16-color palette]] 
{| class="wikitable sortable" style="text-align:center"
|+ Default EGA 16-color palette, matching [[Color Graphics Adapter|CGA]] colors
|-
! Index
! Default palette number
! Default palette color
! rgbRGB
! Hexadecimal
|- style="color: white;" bgcolor="#000000"
| 0
| 0 || align="left" | Black || 000000 
| #000000
|- style="color: white;" bgcolor="#0000AA"
| 1
| 1 || align="left" | Blue || 000001 
| #0000AA
|- style="color: white;" bgcolor="#00AA00"
| 2
| 2 || align="left" | Green || 000010 
| #00AA00
|- style="color: white;" bgcolor="#00AAAA"
| 3
| 3 || align="left" | Cyan || 000011 
| #00AAAA
|- style="color: white;" bgcolor="#AA0000"
| 4
| 4 || align="left" | Red || 000100 
| #AA0000
|- style="color: white;" bgcolor="#AA00AA"
| 5
| 5 || align="left" | Magenta || 000101 
| #AA00AA
|- style="color: white;" bgcolor="#AA5500"
| 20
| 6 || align="left" | Brown || 010100 
| #AA5500
|- style="color: black;" bgcolor="#AAAAAA"
| 7
| 7 || align="left" | White / light gray || 000111 
| #AAAAAA
|- style="color: white;" bgcolor="#555555"
| 56
| 8 || align="left" | Dark gray / bright black || 111000 
| #555555
|- style="color: white;" bgcolor="#5555FF"
| 57
| 9 || align="left" | Bright Blue || 111001 
| #5555FF
|- style="color: black;" bgcolor="#55FF55"
| 58
| 10 || align="left" | Bright green || 111010 
| #55FF55
|- style="color: black;" bgcolor="#55FFFF"
| 59
| 11 || align="left" | Bright cyan || 111011 
| #55FFFF
|- style="color: black;" bgcolor="#FF5555"
| 60
| 12 || align="left" | Bright red || 111100 
| #FF5555
|- style="color: black;" bgcolor="#FF55FF"
| 61
| 13 || align="left" | Bright magenta || 111101 
| #FF55FF
|- style="color: black;" bgcolor="#FFFF55"
| 62
| 14 || align="left" | Bright yellow || 111110 
| #FFFF55
|- style="color: black;" bgcolor="#FFFFFF"
| 63
| 15 || align="left" | Bright white || 111111 
| #FFFFFF
|}

The following images illustrate the full EGA palette in detail.
[[File:EGA Table.svg|left|thumb|Full 64-color EGA palette table]]
<gallery mode="packed" widths="240" heights="160">
File:EGA64 Full Palette.png|Full 64-color EGA palette illustration
File:Ega palette color test chart.png|Full 64-color EGA palette test card
File:Screen color test EGA 16colors.png|Screen color test with custom EGA palette
</gallery>
{{clear}}

=== Specifications ===
[[File:Numbered DE9 female Diagram.svg|thumb|right|EGA connector pinout when looking at back of computer]]
EGA uses a female nine-pin D-subminiature ([[DE-9]]) connector for output, identical to the CGA connector. The signal standard and pinout is backward-compatible with CGA, allowing EGA monitors to be used on CGA cards and conversely.

When operating in EGA modes, pins 2, 6 and 7 are repurposed for EGA's secondary RGB signals (see pinout table below). When operating in 200-line CGA modes, the EGA card is fully backward compatible with a standard IBM CGA monitor; however, third-party monitors had varying compatibility.{{Citation needed|date=August 2020}}

[[File:Tvm-md-3-prevga-monitor-front-and-rear.jpg|thumb|right|Front and rear views of the TVM MD-3, a third-party EGA monitor. DE-9 input, mode switch, contrast and brightness controls at front, V&nbsp;size and V&nbsp;hold knobs at rear.]]

Third-party monitors sometimes connected pin two to ground internally. When connected to an EGA card, this shorts the EGA's secondary red output to ground and can damage the card. Also, some monitors were wired with pin two as their sole ground, and these will not work with the EGA.{{Citation needed|date=August 2020}}

Conversely, an EGA monitor should work with a CGA adapter, but if it is not set to CGA mode, the secondary red signal will be grounded (always zero), and the secondary blue will be floating (unconnected), causing all high-intensity colors except brown to display incorrectly, and all colors to potentially have a variable blue tint due to the indeterminate state of the unconnected secondary blue.{{Citation needed|date=August 2020}}

The IBM 5154 EGA monitor has a special IBM 5153 CGA compatibility mode when operating with CGA sync signals and automatically changes to the CGA pinout to avoid all of the mentioned problems when operating in this mode.<ref>IBM Options and Adapters, Volume 1, "Enhanced Color Display", page 4: "When operating in Mode 1, the display maps the 4 input bits into 16 of the possible 64 colors as shown in the following chart." August 2, 1984.</ref>
{| class="wikitable"
|+ EGA DE-9 connector pin signals
|-
! Pin
! Name
! EGA modes
! CGA compatible modes
|-
| 1
| GND
| Ground
| Ground
|-
| 2
| SR
|style="background-color:#fe0000; color:#ffffff;"| Secondary Red (Intensity)
| Ground
|-
| 3
| PR
|style="background-color:#9a0000; color:#ffffff;" | Primary Red
|style="background-color:#9a0000; color:#ffffff;" | Red
|-
| 4
| PG
|style="background-color:#009901; color:#000000;" | Primary Green
|style="background-color:#009901; color:#000000;" | Green
|-
| 5
| PB
|style="background-color:#010066; color:#ffffff;" | Primary Blue
|style="background-color:#010066; color:#ffffff;" | Blue
|-
| 6
| SG
|style="background-color:#00fe01; color:#000000;" | Secondary Green (Intensity)
|style="color: white; background: #555;"| Intensity
|-
| 7
| SB
|style="background-color:#0000fe; color:#ffffff;" | Secondary Blue (Intensity)
| ''Reserved''
|-
| 8
| H
| Horizontal sync
| Horizontal sync
|-
| 9
| V
| Vertical sync
| Vertical sync
|}
The original IBM EGA card includes a [[feature connector]] (blue connector J4, see first photo on this page), providing access to two [[RCA connector|RCA connectors]] at the back of card, in addition to several analog and digital signals that the EGA adaptor can be configured to use.<ref>{{Cite book |url=https://minuszerodegrees.net/oa/OA%20-%20IBM%20Enhanced%20Graphics%20Adapter.pdf |title=IBM Enhanced Graphics Adapter |publisher=IBM |date=August 2, 1984 |pages=76–78}}</ref> 

A [[light pen]] interface was also present on the original card.<ref>{{Cite book |url=https://minuszerodegrees.net/oa/OA%20-%20IBM%20Enhanced%20Graphics%20Adapter.pdf |title=IBM Enhanced Graphics Adapter |publisher=IBM |date=August 2, 1984 |pages=84}}</ref> 

=== Memory mapping ===
For color text and CGA graphics modes, video memory is mapped to 16&nbsp;KB of addresses beginning at address B8000h, and in monochrome (MDA-compatible) text mode, video memory occupies 16&nbsp;KB beginning at B0000h. These address mappings are for backward compatibility.

For modes new to the EGA, the video memory begins at address A0000h and occupies 64&nbsp;KB. The different base addresses for color vs. monochrome modes makes it possible for an EGA to be used simultaneously with a monochrome graphics card in the same computer, or for an EGA in MDA text mode to be used simultaneously with a CGA in the same computer.

EGA's native graphics modes are [[planar (computer graphics)|planar]], as opposed to the interleaved CGA and [[Hercules Graphics Card|Hercules]] modes. Video memory is divided into four "planes" (except {{resx|640×350}}&nbsp;×&nbsp;2, which has one plane), one for each component of the RGBI color space. Each pixel is represented by one bit in each plane. If a bit in the red plane is on, but none of the equivalent bits in the other pages are, a red pixel will appear in that location on screen. If all the other bits for that particular pixel were also on, it would become white, and so forth.

Planes are different sizes depending on the mode:
{| class="wikitable"
|+ EGA video plane sizes
! Mode
! Plane size
|-
| 200-line modes,<br/>{{resx|640×350}}&nbsp;×&nbsp;2 mode
| 8 KB
|-
| {{resx|640×350}} with 64 KB RAM
| 16 KB
|-
| {{resx|640×350}} with 128 KB RAM
| 32 KB
|}
All planes reside at segment A000 in the CPU's address space. They are bank-switched, and only one plane can be read on the CPU bus at once<!--Though internally, the EGA always reads all 4 planes at once and stores the byte read from each plane in the Graphics Controller data latch for that plane, regardless of which plane is selected to be read on the [CPU] I/O bus-->; however, the programmer may set the control registers on the card to select which planes are written to and write to several at once. An exception is read mode&nbsp;1, in which all four planes are read and compared with programmed "Color Compare" data, and a byte indicating the result of comparing all four planes can be read on the I/O bus.

==See also==
{{Commons category|EGA}}
* {{interlanguage link|JEGA|ja|Japanese Enhanced Graphics Adapter}} (Japanese Enhanced Graphics Adapter for [[AX architecture|AX]] computers)
* [[Video card]]
* [[Graphics display resolution]]
* [[Graphics processing unit]]
* [[List of video connectors|List of display interfaces]]
* [[List of monochrome and RGB color formats#6-bit RGB|List of monochrome and RGB color formats]]{{snd}}6-bit RGB section
* [[List of 16-bit computer color palettes#EGA|List of 16-bit computer color palettes]]{{snd}}EGA section
* [[Professional Graphics Controller]]
* [[Hercules InColor Card]]
* [[VGA compatible text mode]]{{snd}}EGA's own modes are just a subset, and all features are nearly the same
* [[List of defunct graphics chips and card companies]]

== References ==
{{reflist|30em}}{{refbegin}}
* {{cite book |title=Upgrading and Repairing PCs |edition=second |last=Mueller |first=Scott |year=1992 |publisher=Que Books |isbn=0-88022-856-3 |url-access=registration |url=https://archive.org/details/upgradingrepairi0000muel_2ndedition }}
{{refend}}

== External links ==

* [https://web.archive.org/web/20110820211626/http://www.lauppert.ws/screen1/ega/ Representative screenshots of EGA games]

{{Computer display standard}}
{{IBM personal computers}}

[[Category:Computer display standards]]
[[Category:IBM video hardware]]
[[Category:Graphics cards]]
[[Category:Computer-related introductions in 1984]]