CPU: INTEL CORE I5-2500K ($209.99)
When processor price wars happen, they typically take place at or around the $200 mark. It's the sweet spot for consumers on a tight budget, mostly because it tends to be populated by high-end CPU architectures with a little less power than the $300 to $600 flagship models. The i5-2500K is just such a chip, and it has quickly developed a reputation as the best value Sandy Bridge processor. In its stock configuration, it runs four cores at 3.3GHz each, but the heart of its widespread appeal is in this CPU’s ability to operate at speeds of 4GHz and above. The K in the model number denotes the unlocked multiplier on the 2500K, which will allow you to overclock it to your heart’s content (or, more realistically, as far as your cooling will allow).
If you have extra room in your budget, you can step up to the Core i7-2600K ($320), which adds some extra cache (super fast on-chip memory), accelerates the stock speed, and seems to have a slightly higher overclocking ceiling. Hyper-Threading is also available on the 2600K, meaning it can perform two tasks per core for a total of eight threads, but that hasn’t shown itself to be much of an advantage in gaming. Alternatively, you can go nuts and spend $1,050 on the six-core Core i7-3960X Extreme Edition processor that Intel introduced recently — we’d hardly call it good value for money, but out of the box it's the fastest thing you can buy right now. AMD is producing some interesting parts too, however they’re just not competitive enough with Intel’s well-priced inventory to merit an endorsement.
The "clock" of any processor is the frequency at which it operates, as measured in hertz (or cycles per second). An obvious, though rarely linear, improvement you can make to your PC’s performance is to increase that frequency so that it works faster. That’s all overclocking is, you’re just raising the operational speed in the hope of obtaining a tangibly faster user experience. As with humans, however, a processor that works faster is also working harder, leading to proportional increases in power consumption and heat emission. If you’re not ready or willing to deal with the risks of destroying your computer in the effort of finding out its performance limits, we’d advise sticking to the stock settings.
Some manufacturers do provide pre-overclocked designs, such as graphics board makers who might take a reference chip from AMD or Nvidia and run it faster than recommended speeds after upgrading the cooling and power-regulating components. AMD and Intel also have dynamic overclocking systems for their latest generations of CPUs, which disable some cores in order to provide enough thermal and power overhead to reach higher speeds. The difference between manufacturer-provided overclocks and the DIY version is obvious: the former is much more rigorously tested and doesn’t run the risk of voiding your warranty.