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When Frame Rates Aren't What They Seem...

Challenging FPS: Testing SLI And CrossFire Using Video Capture

We've known about the existence of Nvidia's frame metering technology for years, and its efforts to quantify the benefits of spacing frames out evenly, minimizing dropped and runt frames, for months. It was only recently, however, that the company was willing or able to show off the fruits of its development efforts. Even today, the tools can be a little finicky. We would have had even more performance data, even, except that our X79 Express-based benchmark platform was spitting out FCAT data that clearly wasn't right. Switching over to Z77 Express at the last minute gave us the results we were looking for.

As we expected, both from The Tech Report's background with this and Nvidia's in-house examples, we see that AMD's Radeon HD 7870s in CrossFire tend to suffer more dropped and runt frames than a pair of GeForce GTX 660 Tis in SLI. This addresses much of the trepidation about multi-card configurations expressed in Best Graphics Cards for the Money, confirming that two of Nvidia's boards appear more appealing. AMD even admits it's playing catch-up in this area, and is addressing its shortcomings through successive driver improvements.

The Datapath card we used for video captureThe Datapath card we used for video capture

In any case, it's telling that Nvidia put in all of this effort to quantifying graphics performance in a scientifically sound way. The company deserves credit for putting resources into something we wouldn't have been able to develop on our own, even if its motivation wasn't altruistic. The fact is that FCAT gives us a tool for evaluating something we couldn't accurately measure before. We now have two Tom's Hardware labs enabled with the hardware and software to run tests using FCAT, and we're already in the process of testing for a much more comprehensive Part 2.

Having said all of that, we're once again left with questions, even as we uncover a number of answers. While it seems obvious that a runt frame of fewer than 21 scan lines contributes little (or nothing) to the smoothness of a game, would a hardcore gamer see a quality improvement if we split the screen evenly by two, three, or even 50 frames composed of 22 or more lines on the screen? The FCAT tool is built to facilitate user-specified definitions of how large a runt frame can be, and we'll need to play with the script's switches to really dial-in our own recipe for performance evaluation. What we're presenting today is really what FCAT can do out of its proverbial box.

But questions like that tell us we have a lot more work to do. Hopefully, innovative tools like Nvidia's FCAT help us solve them. Keep an eye on this space for our upcoming follow-up.

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