Definition

RAMDAC (random access memory digital-to-analog converter)

Part of the Microprocessors glossary:

RAMDAC (random access memory digital-to-analog converter) is a microchip that converts digital image data into the analog data needed by a computer display. A RAMDAC microchip is built into the video adapter in a computer. It combines a small static RAM (SRAM) containing a color table with three digital-to-analog converters that change digital image data into analog signals that are sent to the display's color generators, one for each primary color - red, green, and blue. In a cathode ray tube (CRT) display, an analog signal is sent to each of three electron guns. With displays using other technologies, the signals are sent to a corresponding mechanism.

How It Works

The SRAM part of the RAMDAC contains a color palette table. A logical color number in the digital data input to SRAM is used to generate three separate values obtained from the table - one for each of red, green, and blue - that are output to one of three digital-to-analog converters. The analog signal output from the converter is input directly to the display electron guns or other image projecting mechanisms.

For displays with true color, the digital color data is fed directly to the DACs, bypassing the SRAM table, which is not needed.

This was last updated in September 2005
Contributor(s): Vladimir Dyo, J. R. Ramirez, and Jeff Stevens
Posted by: Margaret Rouse

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