What is CGA?

Video Graphics Specifications
Creator :	IBM
Year Introduced :	1981
Video Standard :	CGA - Color Graphics Adapter
Horizontal Frequency :	15.7 kHz
Vertical Frequency :	60 Hz
Video RAM :	16K
Maximum Colors :	4
Maximum Resolution :	320x200
Starting Address :	B8000
Connector Type :	DB9
Video Signals :	4 TTL
Status :	Obsolete

Color Graphics Adapter

     Medium resolution IBM graphics standard capable of displaying 640 x 200 pixels in 2 colors, or 320 x 200 pixels in 4 colors.
     One of IBM's earliest hardware video display standards for use in IBM PCs. CGA can display 80*25 or 40*25 text in 16 colors, 640*200 pixels graphics in 2 colors or 320*200 in 4 colors. It is now obsolete.
     Color Graphics Adapter (CGA) The color graphics adapter (CGA) was, at one time, the most common graphics adapter available. It supports an RGB monitor with a maximum resolution of 640 x 200 pixels. The CGA card has two modes of operation: alphanumeric (A/N) and all points addressable (APA). In both modes, the basic character set is formed with a resolution of 8 x 8 pixels. The CGA card displays either 40 or 80 columns with 25 lines of text. In the A/N mode, the CGA card can display up to 16 colors. The all points addressable mode of operation can address each pixel individually. The CGA APA mode supports two resolutions on the screen: medium and high.

DB-9 pins for CGA
Pin	Description
1	Signal ground
2	Signal ground
3	Red video
4	Green video
5	Blue video
6	Signal intensity
7	Unused
8	Horizontal sync
9	Vertical sync

C A U T I O N

Never run your monitor out of spec. If your display is screwed up, there's a good chance that the frequencies are out, so turn off the monitor!

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