How To Buy A Graphics Accelerator

Find the Right Color Depth

Although 8-bit boards capable of 256 colors are adequate for Windows and general-purpose applications, consider stepping up to a 16-bit board with 64,000 colors. Ideal for multimedia applications, 16-bit color requires 2 MB of VRAM for 1024 by 768 resolution. For Windows users, the greater color depth avoids the distracting "color flash" that 8-bit boards can produce when you change windows or move among multiple open applications.

Which Bus Is Best?

Overall, little performance difference exists between the fastest ISA, EISA, and VL-Bus graphics accelerators when you run at a relatively small color depth, such as 1024 by 768 pixels with 256 colors. But when you increase the color depth to 24 bits, you will see some significant performance differenc es between ISA and the other bus types. Therefore, if you're only using 256 colors in your applications and you have an ISA system, the inexpensive ISA-based cards should serve you well.

When Is VL-Bus a Must?

VL-Bus cards can become faster as you add memory to your system. This speed benefit comes because properly designed applications will use available system memory to cache screen information that can then be quickly copied to the screen. This image copying (called Blting) is what really separates VL-Bus cards from other cards: Speedups of over 2 to 1 are common for this operation.

How Much Memory?

Be wary of misleading vendor claims. A board may be advertised as being able to display 16.7 million colors. However, if the board only has 1 MB of video memory, then this color level is possible only at the undesirable resolution of 640 by 480 pixels. If you need lots of color, use the following table as a guide to determine your minimum memory needs.

Consider Support

Be sure tha t your vendor is able to provide you with updated drivers in a convenient manner. Often substantial performance gains will result from the latest, more efficient drivers. On the other hand, high-performance Windows drivers are immensely complex, so there's always a chance that some bug will prevent correct operation, and you should be able to download company fixes quickly.

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Video memory

If you                And you               Video memory
run this              use this              should be
resolution            many colors           at least


640 by 480            16.7 million          1 MB


800 by 600            64,000                1 MB
800 by 600            16.7 million          2 MB


1024 by 768           256                   1 MB
1024 by 768           64,000                2 MB
1024 by 768           16.7 million          3 MB


1280 by 1024          256                   2 MB
1280 by 1024          64,000                3 MB
1280 by 1024
          16.7 million          4 MB