Video accelerators

J.B. MilesSpecial to GCNEven if you're not a PC gamer or professional computer-aided designer, your PC or workstation could be struggling under a heavy graphics load. If this is true, it's probably time to replace the video card that came with your system.Video cards'also known as video accelerators, video adapters, video boards, graphics cards, graphics accelerators or graphics adapters'can make or break your ability to work in graphics programs. They come with their own powerful processors and take over most of the display-related functions from the host CPU.The burden of graphics processing is assigned to the video card's chip set. After the graphical data is processed, it is stored in the card's frame buffer. When the time comes for it to be displayed, the data is transferred to the card's RAM digital-to-analog converter chip, where the digital information is converted to analog signals for use by the computer's analog monitor.The idea behind all this is to relieve the host CPU from the burden of graphics processing so that the entire system runs faster and 2-D and 3-D graphics and video output come alive with exquisite detail, clarity and color.This is all many people want or need to know about video cards, but knowing more could help you avoid wasting money on a card that doesn't suit your computing requirements.Buying a new video card is a little like buying a new car. Some buyers peek at the engine first; others begin with different performance-related details, such as suspension, balance and transmission type. Still others look first at cosmetic details such as color and body style. For both automobiles and video cards, I recommend starting with the engine. A video card's engine is its chip set. As you can imagine, for simply handling daily chores'traditional office word processing or downloading e-mail'its processing power and speed aren't all that important. But for more complex tasks, a powerful graphics engine becomes essential.The latest generation of graphics chip sets, such as those made by 3dfx Interactive and S3 Inc., easily provides high resolutions at high color depths (millions of possible color combinations). They produce great-looking images packed with detail and brilliant colors.Most of the cards listed in the accompanying table offer maximum resolutions of 2,048 by 1,536 pixels, with maximum color depths of 32-bits. For most purposes, a resolution of 1,920 by 1,440 is more than adequate.High-end cards with 64-bit color depths are available, but except for fancy gaming and some very high-end graphics tasks, most users won't require this much. But don't buy a card offering less than a 16-bit color depth, unless you own an aging PC with an old VGA monitor.And if you've ever struggled along with a PC with a monitor-video card combination offering a very low refresh rate, you'll know what eyestrain can do to your level of productivity. Any modern video card should offer a refresh rate of at least 75 hertz at the resolution your monitor is set for. Note the reverse correlation between resolution and refresh rate'the higher the resolution, the slower the refresh rate'and set your system accordingly.Check the specifications of your video card. Good cards often come with 2-D and 3-D matrices showing refresh rates at different resolutions. To make a very long story short, a card needs lots of RAM to provide a buffer for the millions of pixels that are included in high-resolution graphics with millions of color options. You want as much memory as possible.Not long ago, a video card with 8M of RAM was considered top-of-the-line. Plenty of these are still available for well under $100 and are perfectly suitable for common office applications. But if you're moving up, don't buy a card with less than 16M of RAM. For high-end 2-D CAD and modeling tasks, or for 3-D gaming, don't buy a card with less than 32M of RAM. And buy even more RAM if you can afford it.There are several different types of RAM to consider. Most video cards today use synchronous dynamic RAM. A few use synchronous graphics RAM, which is a little faster than SDRAM but also more expensive.The newest, and best, memory architecture used in video cards is double-data-rate, or DDR, SDRAM, which effectively doubles memory speed by enabling two memory operations to take place for each clock cycle of the processor. Used with Accelerated Graphics Port video cards, DDR technology provides the fastest graphical data throughput available. AGP vs. PCI. The 32-bit PCI bus was developed to replace the 16-bit ISA bus, which proved too slow for most current graphics applications. Then along came Accelerated Graphics Port, which provides the fastest-yet data pipeline from the video card to system RAM. The 4X AGP bus currently represents the cutting edge of video card technology and will likely hold that title until the next best bus architecture replaces it.Both PCI and AGP buses are 32 bits wide, but current AGP data transfer rates are either two times or four times faster than PCI. A 2X AGP bus enables transfer rates of 566 megabytes/sec, and a 4X AGP doubles that to more than 1 gigabyte/sec. Virtually all 4X AGP cards can drop back to 2X AGP transfer speeds.Most new PCs and workstations come with at least one AGP port, and it won't be long before vendors stop making PCI versions. But if you have an older PC, replacing a PCI card with an AGP version may pose some problems, because AGP cards can only be used in a PC equipped with an AGP port.Another potential problem is that if your AGP chip set is hardwired to the motherboard of your new PC, it can't be upgraded without changing the entire motherboard. One solution is to bypass the AGP card with a PCI card, but in this case you lose the advantages that AGP brings to the plate. The faster the RAM digital-to-analog converter chip, the faster the digital instructions will be converted to images on your computer screen. Older, slower 8M video cards slogged along with RAMDAC speeds of less than 150 MHz; virtually all the units listed in this guide operate at 300 MHz or 350 MHz. That's enough speed to move mountains of pixels in a hurry. Two major standards for application programming interfaces apply to video cards.Microsoft's DirectX 7.0 is virtually ubiquitous and should be included in the API set of any video card you buy. SGI's OpenGL is less common but ought to be included in a card used for gaming purposes.3dfx Interactives GLide and MiniGL are APIs designed by the company for its Voodoo series of graphics cards. They are similar to OpenGL, but not as widely used. A fairly arcane set of definitions comes with a detailed understanding of video card technology.Only the most dedicated gamers or graphics design cognoscenti need to know them, but check the 3dfx and Matrox Graphics Inc. Web sites for some excellent glossaries of technical terms used in the industry.Your selection of a video card should depend largely on the purposes for which it will be used.The cards listed in this guide will meet moderate-to-heavy 2-D and 3-D graphics and video requirements and are generally priced between $100 and $300.If you have an old PC used for office applications with few graphics involved, save your money and keep your old card. Just replace the entire PC when it's no longer useful.For slow, 133-MHz to 233-MHz Intel Pentium II or Advanced Micro Devices Inc. K-6 workstations, a graphics card with 8M to 16M of RAM will handle limited graphics and video for well under $100.'These can be purchased from almost all of the vendors listed.At the other end of the scale, graphics professionals working on high-end workstations should consider a very powerful graphics accelerator designed specifically for CAD or specialized video editing. These generally cost $800 or more and also are available from most of the vendors listed.XXXSPLITXXX-XXXSPLITXXX-