Video memory is RAM installed on a video adapter. Before an image can be sent to a display monitor, it is first represented as a bit map in an area of video memory called the frame buffer. The amount of video memory, therefore, dictates the maximum resolution and color depth available.
With a conventional video adapter, the bit map to be displayed is first generated by the computer’s microprocessor and then sent to the frame buffer. Most modern video adapters, however, are actually graphics accelerators. This means that they have their own microprocessor that is capable of manipulating bit maps and graphics objects. A small amount of memory is reserved for these operations as well.
Because of the demands of video systems, video memory needs to be faster than main memory. For this reason, most video memory is dual-ported, which means that one set of data can be transferred between video memory and the video processor at the same time that another set of data is being transferred to the monitor. There are many different types of video memory, including VRAM, WRAM, RDRAM, and SGRAM.