What is RAMDAC ?

 RAMDAC (random access memory digital-to-analog converter) is a microchip that convertsdigital image information in to the analog data needed by a computer display that makes use of analog inputs such as CRTdisplays. A RAMDAC microchip is built in to the video adapter in a computer. It combines a tiny static RAM (SRAM) containing a color table with digital-to-analog

converters that alter digital picture information in to analog signals that are sent to the display's color generators, for each primary color - red, green, & blue. Depending on the number of bits used & the RAMDAC-data-transfer rate, the converter will be able to support different computer-display refresh rates. With CRT displays, it is best to work over 75 Hz & seldom under 60 Hz, in order to minimize flicker and with LCD displays, flicker is not a controversy. In a cathode ray tube (CRT) display, an analog signal is sent to each of electron guns. With displays using other technologies, the signals are sent to a corresponding mechanism.

How RAMDAC Works ?

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

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