Graphics subsystem including a RAMDAC IC with digital video storage interface for connection to a graphics bus

摘要

A graphics subsystem including a RAMDAC for connection to a graphics bus implemented on an integrated circuit chip separate from a graphics processor. In one embodiment, the graphics processor is configured to render digital image information in response to graphics commands and to store the digital image information in a memory. The RAMDAC IC includes a conversion unit, which includes a color mapping unit and a digital-to-analog converter and is configured to convert a representation of the digital image information into one or more analog signals for driving a video display. The graphics subsystem further includes a Direct Memory Access (DMA) controller implemented on the second integrated circuit chip. The DMA controller is configured to generate read requests to retrieve the digital image information stored in the memory to thereby cause the digital image information to be provided to the conversion unit. The DMA controller is further configured to generate write cycles to cause digital RGB display data received from the color mapping unit, in the conversion unit, to be provided for storage in a specified region of memory. In another embodiment, the graphics subsystem may include a digital video interface implemented on the second integrated circuit chip. The digital video interface is configured to receive digital RGB display data from the color mapping unit and to provide an encoded digital video output to a digital video output port. The digital video interface is further configured to receive encoded digital video from a digital video input port and to provide decoded digital display data for storage on devices such as a digital VCR.