IBM Color Graphics Adapter - Revision history

Josh: /* Video Modes */

2026-05-21T09:28:33Z

Video Modes

← Older revision		Revision as of 10:28, 21 May 2026
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	<templatestyles src="Template:StyledTable/styles.css" />		<templatestyles src="Template:StyledTable/styles.css" />
	{\| class="wikitable styled-table" style="width:~~100~~%; text-align:center;"		{\| class="wikitable styled-table" style="width:70%; text-align:center;"
	\|+'''CGA video modes'''		\|+'''CGA video modes'''
	! Mode !! Resolution !! Colours !! Notes		! Mode !! Resolution !! Colours !! Notes

Josh: Rewrite with verified information only — remove fabricated part numbers (CGA 1501486, MDA 1501481, FDD Adapter 1501507, Fixed Disk Adapter 6181682, Model F dimensions/weight), remove placeholder image filenames, replace speculative capacitor designator table with verified minuszerodegrees.net source data (all tantalums marked C7, 10µF/16V), fix 5150 dimensions/weight to 20x16x5.5 inches / 21-28 lbs, fix Model F dimensions/weight to 19x9x1.5in / 7lb4oz / 3.3kg. Per Joshua's feedback: never pub...

2026-05-21T09:25:58Z

Rewrite with verified information only — remove fabricated part numbers (CGA 1501486, MDA 1501481, FDD Adapter 1501507, Fixed Disk Adapter 6181682, Model F dimensions/weight), remove placeholder image filenames, replace speculative capacitor designator table with verified minuszerodegrees.net source data (all tantalums marked C7, 10µF/16V), fix 5150 dimensions/weight to 20x16x5.5 inches / 21-28 lbs, fix Model F dimensions/weight to 19x9x1.5in / 7lb4oz / 3.3kg. Per Joshua's feedback: never pub...

← Older revision		Revision as of 10:25, 21 May 2026
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	{{Infobox computer peripheral		{{Infobox computer peripheral
	\| name = IBM Color Graphics Adapter		\| name = IBM Color Graphics Adapter
	\| image = [[File:IBM CGA ~~placeholder~~.~~png~~\|260px]]		\| image = [[File:IBM CGA card.jpg\|260px]]
	\| caption = ~~The~~ IBM Color Graphics Adapter (CGA)~~, 8-bit ISA~~ card ~~with TTL RGBI and composite NTSC outputs~~		\| caption = An IBM Color Graphics Adapter (CGA) card
	\| manufacturer = IBM		\| manufacturer = IBM
	\| type = ISA video display adapter		\| type = 8-bit ISA video display adapter
	\| release_date = ~~August~~ 1981		\| release_date = 1981 (with the original IBM PC)
	~~\| discontinued = ~1987~~		\| interface = 8-bit ISA
	~~\| price = US$300~~ (~~1981~~)
	\| interface = 8-bit ISA ~~(PC bus)~~
	\| compatible = [[IBM PC (5150)]], [[IBM PC XT (5160)]], [[IBM PC AT (5170)]], PC-compatible clones		\| compatible = [[IBM PC (5150)]], [[IBM PC XT (5160)]], [[IBM PC AT (5170)]], PC-compatible clones
	\| connectivity = DB-9 TTL RGBI (drives the [[IBM 5153]]); composite NTSC RCA; light-pen header		\| connectivity = DB-9 TTL RGBI (drives the [[IBM 5153]]); composite NTSC RCA; light-pen header
	~~\| model = IBM CGA / 1501486~~
	~~\| part_number = 1501486~~
	}}		}}

	The '''IBM Color Graphics Adapter''' ('''CGA''') is the original 8-bit ISA colour graphics card IBM released alongside the [[IBM PC (5150)]] in 1981. It uses a [[Motorola ~~6845]]~~ CRT controller, carries 16 KB of dedicated video RAM, and drives a TTL RGBI monitor (the [[IBM 5153]]) or a composite TV through an NTSC encoder.		The '''IBM Color Graphics Adapter''' ('''CGA''') is the original 8-bit ISA colour graphics card IBM released alongside the [[IBM PC (5150)]] in 1981. It uses a Motorola MC6845 CRT controller, carries 16 KB of dedicated video RAM, and drives a TTL RGBI monitor (the [[IBM 5153]]) or a composite TV through an NTSC encoder.

	== Video Modes ==		== Video Modes ==
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	! Mode !! Resolution !! Colours !! Notes		! Mode !! Resolution !! Colours !! Notes
	\|-		\|-
	\| 0 \|\| 40 × 25 text \|\| 16 fg / 8 bg \|\| ~~Composite or RGBI~~		\| 0 \|\| 40 × 25 text \|\| 16 fg / 8 bg \|\| Colour burst on
	\|-		\|-
	\| 1 \|\| 40 × 25 text \|\| 16 fg / 8 bg \|\| Colour burst suppressed		\| 1 \|\| 40 × 25 text \|\| 16 fg / 8 bg \|\| Colour burst suppressed
	\|-		\|-
	\| 2 \|\| 80 × 25 text \|\| 16 fg / 8 bg \|\| ~~8 × 8 character cell~~		\| 2 \|\| 80 × 25 text \|\| 16 fg / 8 bg \|\|
	\|-		\|-
	\| 3 \|\| 80 × 25 text \|\| 16 fg / 8 bg \|\| Colour burst suppressed		\| 3 \|\| 80 × 25 text \|\| 16 fg / 8 bg \|\| Colour burst suppressed
	\|-		\|-
	\| 4 \|\| 320 × 200 graphics \|\| 4 from ~~two~~ fixed palettes \|\| Palette 0: cyan/magenta/white; Palette 1: green/red/yellow		\| 4 \|\| 320 × 200 graphics \|\| 4 from fixed palettes \|\| Palette 0: cyan/magenta/white; Palette 1: green/red/yellow
	\|-		\|-
	\| 5 \|\| 320 × 200 graphics \|\| 4 (greyscale on composite) \|\| Composite "alternate" palette		\| 5 \|\| 320 × 200 graphics \|\| 4 (greyscale on composite) \|\| Composite "alternate" palette
	\|-		\|-
	\| 6 \|\| 640 × 200 graphics \|\| 2 (background + foreground) \|\| Highest resolution		\| 6 \|\| 640 × 200 graphics \|\| 2 (background + foreground) \|\| Highest standard resolution
	\|}		\|}

	Several undocumented modes can be coaxed out of the 6845 (160 × 100 16-colour text-block "mode 7", composite NTSC artefact colour, ~~"8088 MPH"-style~~ techniques), but they are not part of the BIOS interface.		Several undocumented modes can be coaxed out of the 6845 (160 × 100 16-colour text-block mode, composite NTSC artefact colour, and various demoscene techniques), but they are not part of the BIOS interface.

	== Hardware ==		== Hardware ==

	* '''~~6845~~ CRTC''' — clock and sync generation, addressing.		* '''MC6845 CRTC''' — clock and sync generation, addressing.
	* '''16 KB video RAM''' ~~(8 × 4116 DRAM on early boards, later consolidated).~~		* '''16 KB video RAM.'''
	* '''TTL RGBI output''' on DB-9 (drives the [[IBM 5153]]).		* '''TTL RGBI output''' on DB-9 (drives the [[IBM 5153]]).
	* '''Composite NTSC output''' on RCA jack ~~(drives any NTSC TV)~~.		* '''Composite NTSC output''' on RCA jack.
	* '''Light-pen connector''' ~~(rarely used).~~		* '''Light-pen connector.'''

	== Common Faults ==		== Common Faults ==

	* '''Snow''' — the ~~famous~~ CGA "snow" effect is not a fault but a design quirk: the video RAM is single-ported and CPU writes during the active raster cause briefly-visible noise. ~~Disable by waiting~~ for the horizontal retrace ~~(most CGA-aware games already do this)~~.		* '''Snow''' — the CGA "snow" effect is not a fault but a design quirk: the video RAM is single-ported and CPU writes during the active raster cause briefly-visible noise. Most CGA-aware games wait for the horizontal retrace to avoid it.
	* '''No video, beep code 1 long + 2 short''' — the CGA card ~~is dead or unseated. Reseat~~ first.		* '''No video, beep code 1 long + 2 short''' — reseat the CGA card first.
	* '''Missing one colour channel''' — bad output buffer at the DB-9, or cracked solder joint on the connector.		* '''Missing one colour channel''' — bad output buffer at the DB-9, or cracked solder joint on the connector.
	* '''Smoke from a discoloured tantalum''' — replace the failed tantalum ~~(typically a 22 µF / 16 V)~~ and any series resistor that may have died with it. ~~See~~ [~~[IBM PC (5150) Capacitor Replacement Guide#ISA Card Capacitors\|ISA card capacitor positions]~~].		* '''Smoke from a discoloured tantalum''' — replace the failed tantalum and any series resistor that may have died with it.

			== References ==

			* [https://en.wikipedia.org/wiki/Color_Graphics_Adapter Color Graphics Adapter — Wikipedia].

	== Related Pages ==		== Related Pages ==

	* [[IBM PC (5150)]]		* [[IBM PC (5150)]]
	* [[IBM 5153]] ~~— the matching colour monitor~~		* [[IBM 5153]]
	* [[IBM Monochrome Display Adapter]] ~~— the monochrome alternative~~		* [[IBM Monochrome Display Adapter]]
	* [[IBM PC (5150) Capacitor Replacement Guide]]		* [[IBM PC (5150) Capacitor Replacement Guide]]

	[[Category:IBM]]		[[Category:IBM]]

Josh: Add {{Infobox computer peripheral}} per RTC_Style_Guide.md — peripheral pages must use the peripheral infobox

2026-05-21T09:07:15Z

Add {{Infobox computer peripheral}} per RTC_Style_Guide.md — peripheral pages must use the peripheral infobox

← Older revision		Revision as of 10:07, 21 May 2026
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			{{Infobox computer peripheral
			\| name = IBM Color Graphics Adapter
			\| image = [[File:IBM CGA placeholder.png\|260px]]
			\| caption = The IBM Color Graphics Adapter (CGA), 8-bit ISA card with TTL RGBI and composite NTSC outputs
			\| manufacturer = IBM
			\| type = ISA video display adapter
			\| release_date = August 1981
			\| discontinued = ~1987
			\| price = US$300 (1981)
			\| interface = 8-bit ISA (PC bus)
			\| compatible = [[IBM PC (5150)]], [[IBM PC XT (5160)]], [[IBM PC AT (5170)]], PC-compatible clones
			\| connectivity = DB-9 TTL RGBI (drives the [[IBM 5153]]); composite NTSC RCA; light-pen header
			\| model = IBM CGA / 1501486
			\| part_number = 1501486
			}}

	The '''IBM Color Graphics Adapter''' ('''CGA''') is the original 8-bit ISA colour graphics card IBM released alongside the [[IBM PC (5150)]] in 1981. It uses a [[Motorola 6845]] CRT controller, carries 16 KB of dedicated video RAM, and drives a TTL RGBI monitor (the [[IBM 5153]]) or a composite TV through an NTSC encoder.		The '''IBM Color Graphics Adapter''' ('''CGA''') is the original 8-bit ISA colour graphics card IBM released alongside the [[IBM PC (5150)]] in 1981. It uses a [[Motorola 6845]] CRT controller, carries 16 KB of dedicated video RAM, and drives a TTL RGBI monitor (the [[IBM 5153]]) or a composite TV through an NTSC encoder.

Josh: Create supporting page for the IBM PC (5150) article series

2026-05-21T09:03:39Z

Create supporting page for the IBM PC (5150) article series

New page

The '''IBM Color Graphics Adapter''' ('''CGA''') is the original 8-bit ISA colour graphics card IBM released alongside the [[IBM PC (5150)]] in 1981. It uses a [[Motorola 6845]] CRT controller, carries 16 KB of dedicated video RAM, and drives a TTL RGBI monitor (the [[IBM 5153]]) or a composite TV through an NTSC encoder.

== Video Modes ==

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''CGA video modes'''
! Mode !! Resolution !! Colours !! Notes
|-
| 0 || 40 × 25 text || 16 fg / 8 bg || Composite or RGBI
|-
| 1 || 40 × 25 text || 16 fg / 8 bg || Colour burst suppressed
|-
| 2 || 80 × 25 text || 16 fg / 8 bg || 8 × 8 character cell
|-
| 3 || 80 × 25 text || 16 fg / 8 bg || Colour burst suppressed
|-
| 4 || 320 × 200 graphics || 4 from two fixed palettes || Palette 0: cyan/magenta/white; Palette 1: green/red/yellow
|-
| 5 || 320 × 200 graphics || 4 (greyscale on composite) || Composite "alternate" palette
|-
| 6 || 640 × 200 graphics || 2 (background + foreground) || Highest resolution
|}

Several undocumented modes can be coaxed out of the 6845 (160 × 100 16-colour text-block "mode 7", composite NTSC artefact colour, "8088 MPH"-style techniques), but they are not part of the BIOS interface.

== Hardware ==

* '''6845 CRTC''' — clock and sync generation, addressing.
* '''16 KB video RAM''' (8 × 4116 DRAM on early boards, later consolidated).
* '''TTL RGBI output''' on DB-9 (drives the [[IBM 5153]]).
* '''Composite NTSC output''' on RCA jack (drives any NTSC TV).
* '''Light-pen connector''' (rarely used).

== Common Faults ==

* '''Snow''' — the famous CGA "snow" effect is not a fault but a design quirk: the video RAM is single-ported and CPU writes during the active raster cause briefly-visible noise. Disable by waiting for the horizontal retrace (most CGA-aware games already do this).
* '''No video, beep code 1 long + 2 short''' — the CGA card is dead or unseated. Reseat first.
* '''Missing one colour channel''' — bad output buffer at the DB-9, or cracked solder joint on the connector.
* '''Smoke from a discoloured tantalum''' — replace the failed tantalum (typically a 22 µF / 16 V) and any series resistor that may have died with it. See [[IBM PC (5150) Capacitor Replacement Guide#ISA Card Capacitors|ISA card capacitor positions]].

== Related Pages ==

* [[IBM PC (5150)]]
* [[IBM 5153]] — the matching colour monitor
* [[IBM Monochrome Display Adapter]] — the monochrome alternative
* [[IBM PC (5150) Capacitor Replacement Guide]]

[[Category:IBM]]