Overclocking is the action of increasing a component’s clock rate, running it at a higher speed than it was designed to run. This is usually applies to the CPU or GPU, but other components can also be overclocked.
Increasing a component’s clock rate causes it to perform more operations per second, but it also produces additional heat. Overclocking can help squeeze more performance out of your components, but they’ll often need additional cooling and care.
What Is Overclocking?
Your computer’s CPU comes from the factory set to run at a certain maximum speed. If you run your CPU at that speed with proper cooling, it should perform fine without giving you any problems.
However, you’re often not limited to that CPU speed. You can increase the CPU’s speed by setting a higher clock rate or multiplier in the computer’s BIOS, forcing it to perform more operations per second.
This can speed up your CPU — and therefore speed up your computer if your computer is limited by its CPU — but the CPU will produce additional heat. It may become physically damaged if you don’t provide additional cooling, or it may be unstable and cause your computer to blue-screen or restart.
What to Expect From Your Overclocked Processor
Before starting the physical process of overclocking, think about what you’re trying to accomplish. If you use your computer to run standard desktop applications–office productivity apps, Web browsers, and so on–overclocking is not worthwhile, since the higher clock speeds won’t deliver noticeably better performance.
On the other hand, if you run system-intensive applications such as games that hit all of the different subsystems in your PC–hard drive, graphics, memory, and CPU–you’ll see some gain by juicing up the CPU clock, but don’t expect too much. Often, even high-end games are not CPU bound, and they may benefit more from a better graphics subsystem than from overclocking. Still, you’ll see some increase after adjusting the clock speed.
CPU-intensive apps–particularly multithreaded applications–are likely to see the most significant boost from increased clock speed. Photo editing and video transcoding are examples of these types of programs.
Again, however, remember that the ultimate goal is speed with stability. Extreme clock speeds are merely academic exercises if the overclocked system can’t run your applications reliably.
Can You Overclock?
You may not even be able to overclock your CPU. Many motherboards and Intel CPUs ship with locked multipliers, preventing you from tinkering with their values and overclocking your CPU. Intel sells more CPUs with unlocked multipliers, targeted at enthusiasts that want to overclock and squeeze every bit of performance out of the CPU. (Look for CPUs with “K” in their model number.)
If you want to build the most powerful gaming PC imaginable with a water-cooling system so you can push its hardware to the limits with overclocking, you’ll need to take this into account when you buy the components and make sure you buy overclock-friendly hardware. If you have a standard CPU, you probably won’t be able to tinker with it much.
Why You Might Want to Overclock
The advantages to overclocking are clear: You get a faster CPU that can perform more operations per second. However, overclocking has become less critical over time — where overclocking once offered a more responsive desktop and faster performance in Microsoft Office, computers have become powerful enough that most users probably won’t even notice the difference. Your computer is likely bottle-necked by other things — perhaps a mechanical hard drive, if you don’t have solid-state storage — so you may not see a noticeable performance difference most of the time.
Gamers or enthusiasts that want their hardware to run as fast as possible may still want to overclock. However, even gamers will find that modern CPUs are so fast and games are so limited by graphics cards that overclocking doesn’t work the magic it used to. Overclocking a GPU may get you a small increase in performance, though, depending on your system and the games you’re playing.
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.
Myth #3: Overclocking requires expensive motherboards and memory.
Not necessarily. We’ll look at examples involving a fairly high-end motherboard (roughly $250), a $190 board, and a micro-ATX board that’s priced around $140. The $300+ motherboards that gave rise to this myth are luxuries for people bent on extreme overclocking (which requires certain special features). Likewise, unless you want to overclock your DRAM to extreme speeds, modestly priced DRAM (which we’ll be using in our examples) will work fine.
We won’t dive deeply into individual CPU architectures, but you do need to know some basic stuff.
All CPUs have a fundamental clock rate, from which all of the other clock rates inside the CPU are derived. Various sections of the processor take this fundamental clock rate, which acts as a kind of standard timekeeper, and multiply it to get an internal clock speed for a particular section of the CPU. In the Intel Core i5/i7 series of CPUs, the fundamental clock rate is called the base clock or BCLK (it’s usually 133MHz). For its part, AMD calls this rate the CPU bus frequency; it’s commonly set at 200MHz in AMD desktop processors.
Let’s look at the Core i5 750 CPU for a moment. Like almost all Intel CPUs in the Core i5/i7 line, the Core i5 750 has a BCLK of 133MHz. On the other hand, the rated speed of the i750 is 2.66GHz. The main processor takes the BCLK number and multiplies it by 20 to get 2.66GHz (2666MHz)–this is the CPU multiplier. Note that Intel’s latest CPUs also have a feature called Turbo Boost that allows the CPU to run at clock speeds higher than the default speed under certain conditions. For example, when only one core on the Core i5 750 is in use, the Turbo Boost frequency is 3.2GHz.
Most retail processors are clock-locked, which means that you can’t increase the CPU multiplier beyond its rated speed. Some motherboards try to cheat in an effort to unlock the CPU multiplier, but in most instances involving typical retail CPUs, you can’t unlock the multiplier. Admittedly, you can usually set the multiplier to a lower number than the maximum rating, but it’s unclear why you’d want to do this.
You can usually adjust the setting for an Intel CPU’s base clock (BCLK) or for an AMD processor’s CPU bus frequency to any value you want. As with all stages of overclocking, though, you have to be careful here: Changing the underlying fundamental clock frequency will change a host of other parameters. Still, it’s a useful tool to help with overclocking.