How to: Overclocking for newbies

Overclocking refers to pushing your computer components harder and faster than the manufacturer designed them to go. The initial pitch is seductive: Buy a slower, lower-cost CPU; juice up the clock speed; and presto! You have a cheap, high-end processor.

Of course, it's not that simple. Overclocking can certainly speed up your system (and save you some cash in the process), but only if you do it right.

We're going to talk about some of the basics of overclocking--what it really is, some of the basic math behind overclocking and how you might push your own system a little harder and faster. The goal here is to get better, stable performance for your money. After all, it doesn't matter how fast your computer runs if you have to wait for it to reboot from a crash every 10 minutes.

Though overclocking is a complex topic, we'll to keep the discussion here as simple as possible. We won't go into great detail on voltage changes or power issues, or examine the intricacies of memory timing. And we're not going to show you how to get your cheap Celeron up to 8.2GHz.

We will, however, talk about core CPU multipliers and memory clocks, and how the two relate to each other. Memory and CPUs are intricately interconnected, and simply pumping up the speed of one or the other may not yield the performance improvements you want to achieve.

What Is Overclocking?

Simply put, overclocking means setting your CPU and memory to run at speeds higher than their official speed grade. Almost all processors ship with a speed rating. For example, an Intel Core i7 860 runs at 2.80GHz out of the box. Overclocking a Core i7 860 means pushing it to a clock speed higher than 2.80GHz. This article will focus primarily on CPU overclocking to illustrate the core concepts (pun intended).

Processors don't instantly melt when you overclock them because a modern CPU's speed rating specifies the speed at which every processor in the same manufacturing batch cano run--a number that's likely to be considerably lower than the maximum speed that your specific processor is capable of.

In general, CPU yields are so good these days that the nominal speed grade locked into a chip may be far lower than the speed that the chip is capable of running a computer at. In other words, since the statistical distribution in the manufacturing process is skewed toward better-quality chips, odds are that your processor is better than its rated speed.

Disclaimers and Myths

Before we start adjusting core multipliers and memory clocks willy-nilly, let's pause for an important disclaimer:

Overclocking will void the warranty of your retail CPU. Overclocking may destroy your CPU, your motherboard, or your system memory. It may corrupt your hard drive. Be careful when overclocking. You have been warned.

After reading this disclaimer, you may be inclined to walk away. Don't. Moderate overclocking is mostly safe.

These days, Intel and AMD don't frown on overclocking as much as they did a few years ago. Both companies now ship CPUs equipped with core multipliers (which we'll discuss shortly) unlocked, and even CPUs that have locked multipliers are fairly easy to overclock.

First, though, let's take a look at a few overclocking myths.

Myth #1: Overclocking requires expensive liquid cooling or very noisy air coolers.

Actually this isn't a myth if you're planning on doing extreme overclocking. But moderate overclocking (one to two speed grades higher than spec) is often achievable without replacing or supplementing the stock cooler supplied with a retail CPU. On the other hand, a better cooler can extend the life of the product at those higher clock speeds.

Myth #2: Different iterations of the same chip have the same capacity for overclocking.

Because the manufacturing yield is a statistical distribution, you'll probably get a CPU that can run much faster the listed speed, but you might end up with a processor that runs only about 10 percent faster. Consequently, the fact that your buddy down the street can run a Core i5 750 (rated at 2.66GHz) at 4GHz doesn't mean that your Core i5 750 CPU can will be able to run that fast. That caveat is well worth keeping in mind when you attempt to overclock.

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