Left 4 Dead 2
We tested Left 4 Dead 2 by playing back a custom demo using the game's timedemo function. Again, we had all of the image quality options cranked, and we tested with 16X anisotropic filtering and 4X antialiasing. The game's multi-core rendering option was, of course, enabled.

Ah, now here is an example of a GPU bottleneck truly taking over at higher resolutions. Then again, we're talking about a bottleneck that appears to limit frame rates to the mid-90's.

At lower resolutions, we have a dead heat between the Core i3-530 and the Athlon II X4 635, amazingly enough. They're both right in the middle of the pack, though they take very different roads to get there. Judging by the overall results, frame rates in this game are influenced pretty heavily by cache size and core count. The top ranks are populated exclusively by quad-core CPUs with large caches.

Source engine particle simulation
Next up is a test we picked up during a visit to Valve Software, the developers of the Half-Life games. They had been working to incorporate support for multi-core processors into their Source game engine, and they cooked up some benchmarks to demonstrate the benefits of multithreading.

This test runs a particle simulation inside of the Source engine. Most games today use particle systems to create effects like smoke, steam, and fire, but the realism and interactivity of those effects are limited by the available computing horsepower. Valve's particle system distributes the load across multiple CPU cores.

The newer Intel processors seem to gain quite a bit from Hyper-Threading in this test—witness the Core i5-661 nearly matching the HT-less Core i5-750. Astoundingly, the Core i7-975 Extreme achieves over nine times the throughput of the Pentium 4 670.