Video card

Video card is used to generate a video signal and then reads the image on the monitor. It is usually performed in a separate card that is inserted in a special slot on the motherboard. Video card receives commands from the image forming processor, constructs the image in VRAM video memory and converts the contents to a video signal supplied to the monitor.

Video card is used to generate a video signal and then reads the image on the monitor

One of the first video cards for the IBM PC became the MDA (Monochrome Display Adapter) in 1981. It works only in text mode with a resolution 80x25 characters (physically 720x350 pixels) and supports five text attributes: normal, bright, inverted, underlined and blinking. No color or graphics this video card could not make. Hercules company in 1982 released a further development of the MDA graphics card, display adapter HGC (Hercules Graphics Controller), which had a graphical resolution 720x348 points and support two graphics pages. But he was still not allowed to work with color.

The first color graphics card was the CGA (Color Graphics Adapter), released by IBM and became the basis for future standards. It could work either in text mode with the permissions of 40x25 and 80x25 (symbol matrix - 8x8), or graphically with the permissions of 320x200 pixels or 640x200 pixels. In text modes available 256 character attributes - 16 colors and 16 background character color palette was available four colors, four each in 320x200 graphics mode.

Capable of displaying colors and image resolution, ie the number of pixels horizontally and vertically, which you see on the screen, depending not only on the monitor, but also on the card. Modern SVGA video card capable of displaying up to 16.7 million. Flowers with a graphical resolution of 640x480, 800x600, 1026x768, 1280x1024, 1600x1200, 1800x1440 pixels or more.

The video card consists of several components: controller, video memory, digital-to-analog converter with direct access to memory (RAMDAC), and read only memory (ROM video, Video RAM).

The video card with help of controller provides an output image. It determines the speed and capabilities. The video memory stores information about the image. From its volume depends the maximum resolution and the number of colors in the image. RAMDAC converts the digital data stream generated by the controller into an analog signal applied to the monitor. In the video-ROM is video BIOS, service tables, screen fonts, and so on, which can be accessed by the processor.

Modern graphics video card can be composed of a processor accelerator (accelerator) - to perform various operations on the two and three-dimensional graphical objects. In addition, a modern graphics video card in addition to the analog output VGA, DVI has a digital output.

Video card is connected with a special connector to the bus AGP or PCI-Express.

Many modern graphics cards have a TV-out. In addition to it, they have S-Video input to which you can connect a video source - TV, camera - and introduce the image from them to computer.

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