The Valve Particle Simulation Benchmark was developed to showcase processing effects which were added to Half Life 2: Episode 2 and upcoming changes to the Valve Engine. This is a very handy way to test performance with a variety of systems as it utilises multi core processing and particle effects.
The Core i7 875K puts in a great showing with the Valve Particle Simulation Benchmark and when overclocked almost catches up to the ultra high end 980x CPU. The i5-655K also puts in a great showing at just under 5ghz.