3D rendering
Realstorm is not multi-threaded, but it seems to be hitting the same NUMA-based problems we've seen in synthetic benchmarks. The Quad FX was way behind AMD's own Athlon 64 FX-62, and even further behind any Intel Core 2.
Properly multi-threaded 3D renderers are some of the few apps where you get most of the benefit of having extra cores. Pov-ray is more than twice as fast on the Quad FX as it is on an Athlon 64 FX-62, and Cinebench 66 per cent quicker. Cinebench in particular is one area where Quad FX is only a couple of per cent behind Intel's Core 2 Extreme QX6700. But it is still behind, and the QX6700 is running at 2.66GHz where the FX-74 is at 3GHz.