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video memory
bit map
frame buffer
graphics accelerator
main memory
RAMDAC
RDRAM
SGRAM
video adapter
VRAM
WRAM

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 (see table below).

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.

Video RAM Required for Different Resolutions


Resolution
256 colors (8-bit)
65,000 colors (16-bit)
16.7 million colors (24-bit, true color)
640x480512K 1 MB1 MB
800x600512K 1 MB2 MB
1,024x7681 MB 2 MB4 MB
1,152x1,0242 MB 2 MB4 MB
1,280x1,0242 MB 4 MB4 MB
1,600x1,2002 MB 4 MB6 MB


For internet.com pages about video memory, . Also, check out the following links!


More Information

Outstanding Page Guide to video cards
Contains an introduction to video cards, including how they work, and numerous links to explanations on benchmarking and performance, chipsets, CPU, BIOS, and RAM. Updated on Aug 1, 1998

Outstanding Page PC Guide's video card reference
In-depth reference information for video cards. Looks at how the video card works in detail and includes sections on: video memory, interfaces, resolution and color modes, refresh, display standards, 3D computing, and performance issues.

  Video Card Overview
Provides an overview of RAMDAC as well as information about unaccelerated and accelerated video cards, the video chipset, video BIOS, and video memory.

  Video Card Performance
Describes some of the factors relevant to determining a video card's performance including bit width, video memory, system interface, benchmarking video cards, and the importance of drivers. This page is from "The PC Guide."

  Video Memory Function and Speed
Explains what video memory is and what it is used for, as well as looking at the subject of video memory speed. This page is from "The PC Guide."

  Video Memory Technologies
Provides a detailed look at the various memory technologies (DRAM, EDO, VRAM, WRAM, SGRAM, and MDRAM) used on video cards. Also contains a comparison of the most common video memory technologies. This page is from "The PC Guide."

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