IF THE LAUNCH OF Intel's new quad-core Core 2 Extreme QX6700 processor has made one thing clear, it's that some applications are multithreaded, and others are not. Those that are can look forward to a healthy performance boost jumping to four cores, including near-linear scaling in some cases. Those that are not enjoy no such performance benefits, and may even run slower than on the fastest dual-core chips due to the slightly slower clock speeds of Intel's first quad-core offering. Unfortunately, most of today's game engines are among those applications that aren't effectively multithreaded. A handful can take advantage of additional processor cores, but not in a manner that improves performance substantially.

With the megahertz era effectively over and processor makers adding cores rather than cranking up clock speeds, game developers looking to exploit the capabilities of current hardware are faced with a daunting challenge—"one of the most important issues to be solving as a game developer right now," according to Valve software's Gabe Newell. Valve has invested significant resources into optimizing its Source engine for multi-core systems, and doing so has opened up a whole new world of possibilities for its game designers.

You won't have to wait for Half-Life 3 to enjoy the benefits of Valve's multi-core efforts, though. Multi-core optimizations for Source will be included in the next engine update, which is due to become available via Steam before Half-Life 2: Episode 2 is released. Read on to see how Valve has implemented multithreading in its Source engine and developer tools, and how they perform on the latest dual- and quad-core processors from AMD and Intel.