A random-access memory digital-to-analog converter (RAMDAC) is a combination of three fast digital-to-analog converters (DACs) with a small static random-access memory (SRAM) used in computer graphics display controllers or video cards to store the color palette and to generate the analog signals (usually a voltage amplitude) to drive a color monitor. The logical color number from the display memory is fed into the address inputs of the SRAM to select a palette entry to appear on the data output of the SRAM. This entry is composed of three separate values corresponding to the three components (red, green, and blue) of the desired physical color. Each component value is fed to a separate DAC, whose analog output goes to the monitor, and ultimately to one of its three electron guns (or equivalent in non-CRT displays).

RAMDACs became obsolete as DVI, HDMI, DisplayPort and other digital interface technology became mainstream, which transfer video data digitally (via transition-minimized differential signaling or low-voltage differential signaling) and defer digital-to-analog conversion until the monitor's pixels are actuated.

The size of each DAC of the RAMDAC is 6 to 10 bits. The SRAM's word length must be at least three times as large as the size of each DAC. The SRAM acts as a color lookup table (CLUT). It usually has 256 entries (and thus an 8-bit address). If the DAC's word length is also 8 bits, we have a 256 × 24-bit SRAM which allows a selection of 256 out of 16,777,216 (16.7 million) possible colors for the display. The contents of this SRAM can be altered when no pixel needs to be generated for transmission to the display, which occurs during the vertical blanking interval between every frame.

The SRAM can usually be bypassed and the DACs can be fed color directly by display data, for True color modes. In fact this has become very much the normal mode of operation of a RAMDAC since the mid-1990s, so the programmable palette is mostly retained only as a legacy feature to ensure compatibility with old software. In many newer graphics cards, the RAMDAC can be clocked much faster in true color modes, when only the DAC part without the SRAM is used.

For a quick estimation on the pixel clock for a given output, you can do:

Pixels, horizontally, per line × lines, vertically, per display × 1.4 (factor in any blanking) × rate of display updates (refresh rate)

The ability to drive transitions for sharp edges usually incurs, for the RAMDAC, a significant requirement in excess of the pixel clock.

As of 2006, the DAC of a modern graphics card runs at a clock rate of 400 MHz. However, video cards based on the XGI Volari XP10 run at 420 MHz DAC. The highest documented DAC frequency ever achieved on a production video card for the PC platform is 550 MHz, set by BarcoMed 5MP2 Aura 76Hz by Barco.