Video Display Generator

A video display controller or VDC (also regularly called display engine, display interface) is an integrated circuit which is the main component in a video signal generator, a device responsible for the production of a TV video signal in a computing or game system. Some VDCs also generate an audio signal, but that is not their main function.

VDCs were used in the home computers of the 1980s and also in some early video game systems.

The VDC is the main component of the video signal generator logic, responsible for generating the timing of video signals such as the horizontal and vertical synchronization signals and the blanking interval signal. Sometimes other supporting chips were necessary to build a complete system, such as RAM to hold pixel data, ROM to hold character fonts, or some discrete logic such as shift registers.

Most often the VDC chip is completely integrated in the logic of the main computer system, (its video RAM appears in the memory map of the main CPU), but sometimes it functions as a coprocessor that can manipulate the video RAM contents independently

The difference between display controller IC (called display controller, video display controller, display engine, display processor, display interface, etc.) and graphics accelerator IC (called 3D engine) doing calculations regarding 2D or 3D rendering (image generation) and IC doing calculation regarding video compression/decompression algorithms is technically of course is huge. But since all of this logic is usually found on the chip of a graphics processing unit and usually not available separately to the end-customer there is much confusion about these very different functional blocks.

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Wikipedia