Looking at the vast number of graphics cards, I sometimes feel the same way. There are a number of key factors in card evaluation, including clock speeds, memory, memory interface, and adjustability. Here's what you need to know to speak acceleration cards:

CPU makers have long "bin-sorted" their chips. Bin sorting is a process in which chips are run at clock speeds from the highest supported, on down. Chips that pass at, say 500MHz, go in the 500MHz "bin." Chips that don't make that grade get tested at 450MHz and so on. Graphics-chip vendors, and the companies that supply graphics memory, have recently discovered bin sorting. Now, everyone is getting into the act. There's Nvidia, with the TNT2 and TNT2 Ultra. Brash, litigious 3dfx offers the Voodoo3/2000, 3000, and soon, the 3500. Matrox is about to ship the G400 and G400Max.

Then there's memory. I've seen TNT2 boards with 5ns, 5.5ns, 6ns, and 7ns SDRAM, even on TNT2 Ultra boards. Naturally, boards with slower memory will not be quite as speedy as boards with faster RAM.

Some chips run the memory at the same speed as the graphics chip. A good example of this is Voodoo3's synchronous memory interface. So if you get a Voodoo3 model 3000, the chip clock speed (called the core clock) runs at 166MHz. The memory speed (memory clock) is also 166MHz. Other chips, such as the TNT2, have an asynchronous memory interface, allowing memory and core clock speeds to be independent of the other.

The plethora of board makers for TNT2 chips have also added their own brands of user choice Nvidia guarantees the TNT2 Ultra to run at a 150MHz core clock with a 183MHz memory clock - but that's at zero airflow in a small case. Naturally, with a cooling fan and more space around the card, it will run faster. Some card vendors have taken advantage of this and are either shipping at a higher clock rate or supplying tools to let users make their own clock-rate changes. Diamond's control panel is the most conservative, with five presets that adjust both core and memory clock. Hercules is probably the most aggressive, allowing users to get themselves into big trouble by creating a situation where the system can't even boot. This is pretty rare, though. When I ran up the sliders in the Hercules control panel to their respective maximum, which visibly degraded the image and locked up the system, I was able to boot back into Windows and change it back after leaving the system off for a few minutes.

Not all cards supply convenient tools to the user. Voodoo3 cards don't come with control-panel performance sliders, nor do Matrox, ATI, and several TNT2 cards. It's understandable. While such controls offer freedom to end users, they can create support problems for the card companies. Some users seem to have inflated expectations. I've seen several reports of Hercules TNT2 Ultra cards being returned because they wouldn't run faster than 175MHz. Considering that Hercules guarantees a 175MHz core clock and 200MHz memory clock - already considerably faster than the rated spec - this says something about user expectations.

Then there's the issue of memory speed. All memory is not created equal. Several board vendors have reported that some 183MHz memory can be clocked much higher than some 200MHz RAM. (No, they didn't tell me which brands unfortunately).

For those users who get a card that doesn't have any built-in performance sliders, there are tools available on the Net that lets you DIY. The most popular is Powerstrip, from Entech (www.entechtaiwan.com). It's a nice little tool that lets you tweak a number of graphics settings through a somewhat cluttered user interface. It also supports multiple chipsets, including Voodoo3 and TNT/TNT2.

Whenever you start playing with clock rates, though, be very wary. You may run fine for a few hours, then have inexplicable problems. In our testing, we ran the cards at the highest stable clock rate that could be sustained for a full day, but we didn't test for an extended period of time. So be aware that your mileage may vary.

Next: 32-bit Graphics - The Wave of the Future?