Boards that Accelerate
Professionals, Not Gamers
3D graphic acceleration and AGP interfaces are taking hold of the board arena. Business users donıt require all the 3D bells and whistles, but you can benefit from these technologies. We explore the latest display-enhancing products.
By Liz Levy
August 1998
Graphic accelerator boards are one of those products on a constant evolutionary cycle, with ever-increasing performance and ever-falling prices. Memory and speed increase with every new generation, and the top-of-the-line board of yesterday is the entry-level product of today. Thatıs why professionals should look ahead when it comes to choosing a graphics board.
Graphic boards have many pseud-onyms, including display adapters, display controllers, accelerator boards, monitor boards, etc. All these terms refer to a display adapter that uses a special controller, usually referred to as the chip set, to handle graphic operations.
Ideally, controllers relieve the CPU from these operations, freeing it to perform other tasks. A good graphics accelerator board can, therefore, increase the overall speed of a PC. The main benefits are higher-resolution, better color and faster rendering of 2D and 3D graphics.
The Case For 3D
In Business Applications
A graphic accelerator board is a good investment for those document professionals who need to support a monitor running above the minimum requirements for an imaging application (1,280 x 1,024 at a 75 Hz refresh rate with 16-bit color). These users will usually require 4 BM or 8 MB of memory onboard with fast 2D performance as well as decent support for 3D. These boards run between $130 and $300. Fast 2D-performance improves viewing and lets you click between multiple applications. These boards push monitors to perform at their maximum potential, providing rich true color and supporting high resolutions on large 19ı and 21ı displays.
This is different from the requirements of professional 3D users, such as CAD designers or 3D animators or the average consumer who is primarily concerned with game performance. The professional 3D users require the most sophisticated of graphic accelerators, with 16 MB of memory or higher and the ability to perform high-resolution rendering. These boards cost more than $300.
The use of 3D in the corporate world may grow as applications such as Microsoft Power Point begin to apply 3D techniques to business presentations. 3D enhances visual impact. Three-dimensional spreadsheets, for example, can make information more visually appealing and accentuate relationships between data.
The Internet is quickly becoming a 3D medium. VRML (Virtual Reality Markup Language) authoring tools and VRML Internet browsers on Internet Explorer and Netscape Navigator support 3D Web graphics. Accelerators will speed up the processing of these graphics and enhance the Internet experience.
Mainstream business software vendors have been slow to adopt 3D, but as the installed base of 3D-capable PCs grows, so does the development of 3D-empowered software. Microsoftıs Direct 3D has become a standard that is helping to popularize 3D.
Most graphic board manufactures support Direct3D and OpenGL as their primary APIs (application programming inferface). Direct3D makes 3D technology usable from desktop platforms. Direct3D is currently shipping as part of DirectX 5 for Windows 9X and NT. It is a set of 3D graphics services that support software-based 3D rendering and compatibility with graphic accelerators and software applications.
Direct3D provides access to the advanced graphics capabilities of 3D hardware accelerators including z-buffering, anti-aliasing, alpha blending, mip mapping, atmospheric effects and perspective correct texture mapping. (If you want to know more about these capabilities, refer to the 3D glossary on page 50).
OpenGL from Silicon Graphics is another 3D graphics standard. It is supported by NT, Windows 98 and newer versions of Windows 95. This standard allows users to create 3D graphics and modeling.
The Basics of
Board Performance
The performance of a graphic accelerator board is determined by many factors, such as the chip set, amount and type of memory, and the bus. Chip sets like ATIıs Rage Pro Turbo, nVidiaıs RIVA 128ZX, Intelıs I740 and Number Nineıs Ticket to Ride IV include integrated RAMDACs (digital to analog converters) boasting speeds of 230 MHz to 250 MHz with 64-bit or 128-bit engine design. The number of bits refers to the width of the data path between the controller and the memory.
Controllers determine the speed at which data is written to and accessed from the frame buffer and passed along to the RAMDAC for processing. The frame buffer is a section of the graphics memory where data is written for temporary storage. All VGA-based monitors need analog input. Data is transferred from the frame buffer to the RAMDAC, which converts digital information to an analog signal for the monitor.
A fast RAMDAC supports a high refresh rate. The refresh rate is the measurement of times per second a screen is repainted. This is measured in hertz (Hz). A slow refresh rate will cause the screen to flicker. As a rule, refresh rates of less than 75 Hz can causes eye fatigue from screen flicker. Most people stop seeing the flicker at 60-67 Hz but what is undetectable can still have an affect. Running your monitor at a high refresh rate, about 85 Hz, will give you flicker-free performance and, thus, reduced eyestrain. To run at 1,600 x 1,200 resolution with a refresh rate of 85 Hz, you would need a 234 MHz RAMDAC.
Depending on the boardıs architecture, the controller can move data into memory in up to 128-bit chunks. At any one time, many operations may be competing for bandwidth on the path between the controller and the frame buffer. Itıs important that this pathway is wide enough and that the chips are fast enough to keep up with the flow. Similarly, if the RAMDAC is not fast enough, the path between it and the frame buffer may also become clogged.
In 3D systems, there is an additional requirement for special memory called z-buffer. Z-buffer handles information on the depth of a scene. In some systems, there is also a local texture memory to handle storage of texture maps, which are essential for realism in 3D graphic scenes.
Graphic accelerator board memory goes by many names. The products covered here use either SDRAM or SGRAM, in 4 MB, 8 MB or 16 MB configurations. The SDRAM and SGRAM memory types are more advanced successors of standard DRAM (Dynamic Random Access Memory) with improved performance.
SGRAM can be used for texture and z-buffer storage and is above SDRAM in 3D graphics performance. New boards still use SDRAM for its low cost and high 2D performance. A larger memory will help support the use of higher color depths and more complex 3D graphic data information. To run at 1,600 x 1,200 resolution with 24-bit color, you would need 8 MB of memory on board.
Color depth is the amount of colors displayable on your monitor. An 8-bit color depth equals 256 colors. A 16-bit color depth equals 64K or 64,000 colors. A 24-bit color depth equals 16.7M or 16.7 million colors. Color depth of 24-bit and above is considered true color display. True color is the ability to display the entire range of colors possible.
Resolution, refresh rate and color depth are all very important factors in imaging applications and affect the overall appearance of your monitor. Resolution is the number of horizontal pixels times the number of vertical lines. This gives you the total number of pixels that can be displayed by your monitor. A higher resolution means more information displayed and greater detail. For most imaging applications, running at 1,280 x 1,024 at a 75 Hz refresh rate with 16-bit color is a good place to start.
The interface is another feature important to graphic accelerator board performance. Today thereıs PCI and the newer AGP interface to choose from. Intel announced its AGP (Accelerated Graphics Port) in 1996. It is being promoted as the standard interface to bring real-time 3D to the PC, and itıs included in most Pentium II PCs and more recent boards. AGP 2X is a newer, faster version.
AGP is an extension of the PCI bus that overcomes the limitations of PCI for handling large amounts of 3D graphics data. With AGP, texture memory and z-buffer data can be stored in system memory rather than local memory on the graphic accelerator board itself. This is because AGP is a more direct connection between the board memory and system memory. It also has an increased bus bandwidth and provides much higher data transfer rates than PCI -- 133 MHz versus PCIıs 33-66 MHz.
AGP boards can make more efficient use of frame buffer memory by retrieving and transferring data stored in system memory more efficiently. This improves 2D graphics performance while increasing the flow of 3D data through the system. With the effective use of system memory, high-end AGP boards do not require large amounts of local texture memory and can be manufactured at low costs.
The included software drivers, that are used to install the board and support its features, are vital to the boardıs performance. They tell the operating system how to run the controller and can improve the performance if they let the controller perform specialized functions. Companies usually make regular updates of their drivers available for downloading from their Web sites. Updates can include new software support or enhancements.
If you use video conferencing, consider board extras, like TV-to-monitor converters and video-input support. Graphic accelerator boards not only speed up 2D and 3D performance; they also improve video frame rates.
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