Challenging FPS: Testing SLI And CrossFire Using Video Capture

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

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 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.

  • kajunchicken
    Hopefully someone besides Nvidia develops this technology. If no one does, Nvidia can charge whatever they want...
  • cleeve
    kajunchickenHopefully someone besides Nvidia develops this technology. If no one does, Nvidia can charge whatever they want...
    FCAT isn't for end users, it's for review sites. The tech is supplied by hardware manufacturers, Nvidia just makes the scripts. They gave them to us for testing.
  • cangelini
    kajunchickenHopefully someone besides Nvidia develops this technology. If no one does, Nvidia can charge whatever they want...And actually, it'd be nice to see someone like Beepa incorporate the overlay functionality, taking Nvidia out of the equation.
  • cravin
    I wish there were an easy way to make my frame rates not dip and spike so much. A lot of times it can go up to like 120fps but then dipts down to 60 -70. It makes it look super choppy and ugly. I know I could limit it at 60 frames a second, but wouldn't that just be like vsync? Would that have input lag.
  • DarkMantle
    Good review, but honestly I wouldnt use a tool touched by Nvidia to test AMD hardware, Nvidia has a track record of crippling the competition's hardware every chance they have. Also, i was checking prices in Newegg and to be honest the HD7870 is much cheaper than the GTX660Ti, why didn't you use 7870LE (Tahiti core) for this test? The price is much more closer.
    The problem i have with the hardware you picked for this reviews is that even though, RAW FPS are not the main idea behind the review, you are giving a Tool for every troll on the net to say AMD hardware or drivers are crap. The idea behind the review is good though.
  • krneki_05
    Vsync would only cut out the frames above 60FPS, so you would still have the FPS drops. but 60 or 70 FPS is more then you need (unless you are using 120Hz monitor and you have super awesome eyes to see the difference between 60 and 120FPS, that some do). No, the choppy felling you have must be something else not the frames.
  • BS Marketing
    Does it really matter? Over 60 FPS there will be screen tearing. So why is this sudden fuss? I guess nvidia marketing engine is in full flow. Only explanation is that Nvidia is really scared now, trying everything in there power to deceive people.
  • rojodogg
    I enjoyed the artical and it was very informative, I look forward to more testing of other GPU-s in the future.
  • bystander
    Great article.

    But as great as the review is, I feel one thing that review sites have dropped the ball on is the lack of v-sync comparisons. A lot of people play with v-sync, and while a 60hz monitor is going to limit what you can test, you could get a 120hz or 144hz monitor and see how they behave with v-sync on.

    And the toughest thing of all, is how can microstutter be more accurately quantified. Not counting the runt frames gives a more accurate representation of FPS, but does not quantify microstutter that may be happening as a result.

    It seems the more info we get, the more questions I have.
  • rene13cross
    @DarkMantle, exactly my thinking. I don't want to sound like a paranoid goof who thinks everything is a conspiracy but a test suite created by Nvidia to test AMD hardware doesn't sound like a very trustworthy test. I'm not saying that the results here are all false but Nvidia has had a slight history in the past with attempting to present the competition in an unfair light.