Benchmark Results: DiRT 3
This should set the “expensive DirectCompute” theory to rest once and for all—if we’re talking about discrete graphics. Notice that increasing from High to Ultra HDAO has essentially no impact on performance, despite a considerable increase in workload added by this effect. We see the FX-8150 processor kick out 36% higher frame rates than the mainstream A8-3850, but changing the amount of sampling done for the AO effect has essentially no impact...
...until we switch to the APU. Now we see a 37% difference open up between the High and Ultra settings. Worse, our Ultra mode playability falls to almost 20 FPS on average. That's far lower than we'd be willing to tolerate as gamers. Our only choice would be to pick a lower resolution, since we're already using the most entry-level detail settings.
Taking a comparative look across all three configurations, it’s obvious that the best performance comes from a discrete graphics-equipped machine, where plenty of rendering muscle exposes the biggest difference between ambient occlusion modes. The APU is barely playable at this level, but a game as visually luscious as DiRT 3 deserves to have its bells and whistles turned on for maximum enjoyment, and today’s top-end Llano-based APU simply won’t allow this. We have high hopes for Trinity, though, expected to emerge in the next couple of months with updated processing cores and a more efficient graphics architecture.