CrossFireX Arrives: First Look at 3 and 4 GPUs in 2 Card Setups

S.T.A.L.K.E.R. Performance

Version: 1.0005

Settings: full dynamic lighting, everything maxed without AA and no grass shadows.

For this test, we walk in a straight line for about 30 seconds and use FRAPS to measure performance. We use the same save game every time and the path doesn't change. Our performance measurements are very consistent between runs. We do two runs and take the second.

S.T.A.L.K.E.R. is a strange one when it comes to performance. At some resolutions, quad-GPUs helps somewhat, but generally speaking the sweet spot is three GPUs. What's really perplexing is that we see quad help more at 1280x1024 than at 1600x1200 and 1920x1200. The performance benefits of three GPUs is also a bit erratic; though clearly at 2560x1600 the difference is noticeable, that resolution also demonstrates better scaling from two to three cards than from one to two cards - not something we would normally expect to see.

What we can say for certain is that the latest version of STALKER is not performing as well as we would expect in a variety of ways. It's not unusual to see multi-GPU technologies run into CPU limitations at lower resolutions and offer better scaling at higher resolutions, but that's not what we're seeing. Instead, we have our lowest and highest resolutions benefiting more from CrossFire (and CrossFireX) than our middle resolutions. We are looking into the matter more to see if we can determine what is actually happening; this could be something caused by the Skulltrail platform, the 1.0005 patch, the AMD drivers… or more likely than not all of these things working together.

CrossFireX has the potential to add value at all resolutions in S.T.A.L.K.E.R., but at present there are some anomalies (Ed: the kind they pay good money for around Chernobyl, we hear). Due to the nature of performance, gameplay and location in the game could make for huge variations in performance. Looking at the sky will push frame rate way up into the hundreds, so keeping more sky in your view than ground will improve your framerate. Thus, people who normally look higher while running around will experience better performance than those who look lower.

It's very hard with data like this to accurately assess the value of CrossFireX for this particular game. Based on the data we do have, it again seems that three GPUs is the sweet spot rather than four, in spite of the fact that four GPUs can help at both higher and lower resolutions.

Performance makes sense in general, but it is important to note the sharp relative drop of the 3870X2 at 2560x1600. This is a case where the 3870X2 doesn't appear to have the power to reach the next performance plateau, and adding in another graphics card really made the difference. That, or it's just another driver glitch that needs some ironing.