When you buy a CPU, its manufacturer will list its processing speed in GHz (Gigahertz). Gigahertz is used to represent the number of cycles a CPU can complete per second, with a 4.2GHz CPU being able to complete 4.2 billion cycles per second. Most CPUs offer speeds in the range of 2-3GHz, but some of the highest-end CPUs can reach 5GHz. Obviously, purchasing high-end components costs more money than the mid-tier components, but if you’re willing to change some settings, it is possible to increase the speed of some (but not all) CPUs through a process called “overclocking”.
All CPUs use an internal clock to regulate the speed at which they run, this clock has two parts, the base clock, and the multiplier. The base clock is set by all CPUs to 100MHz (0.1Ghz), this number is then multiplied by the multiplier, to get the final processor speed, called the base processor frequency (confusingly, this multiplied value is also commonly referred to as the base clock). For example, with a base clock of 100MHz and a multiplier of 32, your CPU will have a base frequency of 3.2GHz. Overclocking is the process of modifying the multiplier to get some extra performance out of your processor.
Tip: The base clock of 100MHz is used by many other parts of the computer and modifying this number can cause severe instability and can make your computer unusable. It is highly recommended that you only change the multiplier when overclocking your CPU as this doesn’t directly affect other components.
By modifying the value of the multiplier, you can increase the overall processing speed of the CPU. For example, changing the multiplier from 32 to 40, changes your CPUs speed from 3.2GHz to 4.0GHz, giving you a performance increase of 25%.
Not all CPUs support overclocking, AMD has “unlocked” the multiplier of most of its CPUs but Intel only support overclocking on its CPUs marked with the “K” or “X” label.
Tip: The multiplier being “unlocked” means that it can be modified, if the multiplier is locked you can’t change it and will be unable to overclock the CPU.
Overclocking is typically only supported on desktop CPUs as it can significantly increase the heat that the CPU outputs, as well as the power it requires. As such it is important to ensure that you have a good quality PSU (Power Supply Unit) that can support the extra power load. It is also critical to have a strong cooling solution so you can dissipate the extra heat the CPU will produce. Another factor to consider is that not all motherboards support overclocking, it needs to have a high-quality power delivery system and it needs firmware support.
Tip: It’s important to make sure your PSU can supply enough power for your overclock, typically you should allow around 100 or 200 Watts more than what your computer needs. Some people who have overclocked their AMD Ryzen CPUs have found that their CPUs have increased power consumption from the standard 105W to over 200W.
Before you start overclocking, you should be aware that it does increase the stress on your CPU and can reduce its lifespan, especially if you don’t have enough cooling. You should also be aware that you can’t just set an arbitrary speed, like changing a CPU from 2.4Ghz to 5GHz. Large changes from the default speeds are likely to be unstable, and pushing too hard can permanently damage or break the CPU. If you’re starting out with overclocking, try a conservative increase of a few hundred MHz to start with and then work your way up if your computer is stable and not overheating.
Tip: Modern CPUs generally have a “Boost clock” that allows it to temporarily increase how fast it runs based on temperature headroom and power availability. You shouldn’t try to exceed the boost clock value with your first overclocking attempt as CPUs are only designed to run at that speed temporarily. If your overclock is stable, however, you can try to push your overclock above the boost clock.
Not all CPUs are created equal, some are better at overclocking than others, even within the same product line. Even if you match overclock settings with other users with the same CPU, you may not get stable results, but you should only need relatively minor adjustments to achieve a stable set up.
Changing the speed of the processor does increase its power requirements, one way to help increase stability is to raise the voltage of the power being sent to the CPU. This should only be done in very small steps of 0.005V or less. Increasing the voltage supplied to the CPU will increase your temperatures even if it is running at the same speed, you should aim for the voltage supplied to be as low as possible for the overclock to be stable.
When overclocking you should be wary of your CPUs temperature as it can be damaged by high heat. To protect the CPU from damage, manufacturers have a value called TJMax or Thermal Junction Maximum. When TJmax is reached the CPU will cut its speed to reduce temperatures in a process called thermal throttling. For Intel CPUs, this temperature is 100 or 105 degrees Celsius, for AMD CPUs, this value is 95 degrees Celsius. You should generally aim for your maximum temperature to be 15 degrees below this value when under heavy load.