Onboard Crossfire with R700

PCGH proves micro stuttering on the Radeon HD 4870 X2

In our benchmark review of the Radeon HD 4870 X2 we already mentioned the problem: the micro stuttering did not vanish. Now we deliver the proof.
Radeon HD 4870 X2: micro stuttering is not gone.
Radeon HD 4870 X2: micro stuttering is not gone. [Source: view picture gallery]
In February we wrote: Micro stuttering may destroy the performance gains from current multi GPU technologies. Since the beginning of the year hardware forums all over the world discussed what it's all about the infamous micro stuttering. People called for a "Frametime Harmonizer”, a device that emits the frames of multiple GPUs at regular intervals. The drivers were said to fix the problem. Many people expected a hardware solution with the Radeon HD 4870 X2. But the problem was not fixed (properly).

Test system and methods
After having explained the problem in the X2 review, we now deliver the appropriate pictures. The data below was gathered with the same card, which we unfortunately had to send back already. The Catalyst driver is the very same, too. It is a Beta state piece of software with the internal serial number is 8.52 (Catalyst 8.7: v8.512). To keep the data flowing we used a Core 2 Duo E8500 @ 3.6 GHz (400 x 9).

The frametimes below are taken from Half-Life 2: Episode 2, which we upgraded with the Fakefactory Cinematic Mod 8. In order to receive low framerates, we activated 24x CFAA (8x MSAA plus CFAA and Edge Detection) and 16:1 AF. The charts show the first thirty frames (not seconds!), that we recorded with Fraps. As it turned out that the tool doesn't always record what is displayed on the monitor, we convinced ourselves that the stuttering was there, before we let Fraps do the monitoring and got these results. This is the best way to prove visible stuttering with hard numbers. But not everyone notices the problem. A lot of people don't even recognize the micro stuttering and therefore don't see any differences to normal situations. The trick is not to see that the game stutters but how it does.

Radeon HD 4870 X2: worst case of micro stuttering (picture: PCGH)
Radeon HD 4870 X2: worst case of micro stuttering (picture: PCGH) [Source: view picture gallery]
Radeon HD 4870 X2: worst case of micro stuttering (picture: PCGH)
Radeon HD 4870 X2: worst case of micro stuttering (picture: PCGH) [Source: view picture gallery]

The video shows our benchmark scene in Crysis at 1,680 x 1,050 pixels (DX10, very high) without FSAA or AF. Crossfire is not working properly and therefore the framerate is low - let's call this macro stuttering. In addition to this macro stuttering there is an irregular frame distribution, known as - surprise - micro stuttering. Just compare the video to the insufficient performance of your single GPU graphics card, which will look smoother for sure. The reason for Crossfire to work improperly is a driver bug of course. The visible irregular distribution of displayed frames within the example might make it clear how annoying micro stuttering can be at low fps rates.

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Radeon HD 4870 X2: irregular frame output (micro stuttering)
If compared to the performance of a single GPU card, you will see that the video shows an irregular distribution of the frame output.

Conclusion: micro stuttering
It's not over, yet. Future drivers might make the more popular games run smooth, but a general solution is not insight. As you can see it is a grief problem. Since why should you pay twice the price just to "experience" the same fps as with a less expensive graphics card? The same thing can be said about the Nvidia solution Geforce 9800 GX2 and all graphics cards that can be connected via SLI, too. The Californians find it equally difficult to find a proper solution.

Since we've tested many games, we can say that micro stuttering occurs in Half-Life 2, Crysis, Race Driver Grid, Need for Speed Carbon, TES4: Oblivion and 3D Mark Vantage. To be fair, we have to admit, it takes such demanding settings to bring the HD 4870 X2 to her knees. But in the future, with new games, the fps will decrease. Not later than that time the problem will rise again, while those who use big screens or those fans of FSAA will have to deal with the problem all the time.

Author: Raffael Vötter (Jul 28, 2008)

Mikroruckeln Radeon HD 4870 X2 [199,6 MB]

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