Editing RAMDAC (section)

== History ==
[[file:IMS G171.jpg|thumb|IMS G171 RAMDAC on the VGA board]]

The term ''RAMDAC'' did not enter into common PC-terminology until [[IBM]] introduced the IBM [[Video Graphics Array|VGA]] display adapter in 1987.  The IBM VGA adapter used the [[INMOS]] G171 RAMDAC.  The INMOS VGA RAMDAC was a separate chip, featured a 256-color (8-bit CLUT) display from a palette of {{val|262144|fmt=commas}} possible values, and supported pixel-rates up to approximately 30{{nbsp}}Mpix/s.<ref>{{cite web |url=https://www.computer.org/publications/tech-news/chasing-pixels/Famous-Graphics-Chips-IBMs-VGA |title=Famous Graphics Chips: IBM’s VGA |access-date=2024-04-13}}</ref>

As clone manufacturers copied IBM VGA hardware, they also copied the INMOS VGA RAMDAC.  Advances in semiconductor manufacturing and PC processing power allowed RAMDACs to add ''direct-color'' operation, which is a mode of operation that allows the [[Super Video Graphics Array|SVGA]]-controller to pass a pixel's color value directly to the DAC-inputs, thereby bypassing the RAM lookup-table.  Another innovation was Edsun's CEGDAC, which featured hardware-assisted [[spatial anti-aliasing]] for line/vector draw operations.

By the early 1990s, the PC chip industry had advanced to the point where RAMDACs were integrated into the display controller chip, thus reducing the number of discrete chips and the cost of video cards. Consequently, the market for standalone RAMDACs disappeared.

In modern PCs, the RAMDAC(s) are integrated into the display controller chip, which itself may be mounted on an add-in-board or integrated into the motherboard core-logic chipset.  The original purpose of the RAMDAC, to provide a [[CLUT]]-based display mode, is rarely used, having been supplanted by True Color display modes. However, many [[Computer-aided design|CAD]] and video editing applications use [[hardware overlay]], combined with the programmable palette, to ensure the user interface does not disrupt the rendering of the editing window.