Instructions for CPU overclocking: Whether instead of a new purchase or to sound out the maximum of the new hardware: Overclocking enjoys constant high popularity with PCGH readers. Accordingly, in our survey for the community days “15 years PCGH” the topic of today’s article was most frequently requested: Basics of CPU overclocking.

Many users consider overclocking their PC when performance is no longer sufficient. But a large percentage shrinks from it because the options are too various and the worry is too large that one turns by mistake at a wrong adjusting wheel and the PC blesses the temporal. But this fear is mostly unfounded nowadays because the protection mechanisms of modern CPUs take effect in fractions of a second and usually effectively prevent serious damage.

We, therefore, start at the other end and give a basic overview of the most important settings and things you should consider when overclocking the CPU and give some rough guidelines in the text.

First the obligatory warning: If you overclock, work at your own risk! There is no guarantee that hardware and software will survive the procedures without damage, nor is there any guarantee of long-term stability. Should hardware damage occur due to overclocking, manufacturers or dealers will almost certainly reject guarantees and warranties, provided they can prove the OC to you.

CPU overclock: The right hardware

In addition to good cooling (see next section), a few other things are required for CPU overclocking, which we would like to briefly mention here. Starting with the CPU it should be a C, K or X model in the case of current Intel processors, otherwise it will remain with the anticipation: In other models, not only are the clock multipliers fixed, the system clock can also only be increased within such narrow limits that the possible results have no relevance for the practically tangible performance, because we are talking about a maximum of 5 to 8 percent. If it is a processor from AMD and either bears an “FX” in the name or offers the addition “Black Edition” in the case of older models, you are in good hands: You can not only increase the system clock (this is also possible without Black-Edition/FX), but also the multiplier is freely adjustable for all practical needs.

The motherboard should offer appropriate options, which is nowadays the case with almost all models with the better chips (etchings). “Z” for Intel and “FX” and “X” for AMD are the options of choice, but the H-chips, which are not actually intended for overclocking, also offer OC functions in the UEFI menu, even if this is not actually intended. More importantly, especially in the case of AMD processors, the board also supports CPUs with a TDP of 125 watts, because one thing is almost always the case with the OC: even without an additional voltage increase, the power consumption increases.

For information about supported CPUs, check the compatibility lists on the homepage of the respective mainboard manufacturer.

In addition, there is the electricity supplier. No, not Eon & Co., but the power supply. As already mentioned, the power consumption of the processor and as a result of the entire system will increase. How strong, depends on the degree of overclocking and especially on the strength of the voltage increase. In general, brand power supplies are not specified as close to their performance limits as particularly inexpensive power supplies, which may even be supplied with the case purchase.

CPU overclock: Good cooling

High power consumption generates a high heat development, as the energy supplied is not converted into motion or other forms. This heat must be dissipated promptly by the processor so that it remains within the permitted operating temperature even when overclocked.

The often supplied “boxed” coolers are only suitable for overclocking to a very limited extent, as they usually have difficulty in removing the standard waste heat as quiet as a whisper. If, on the other hand, you invest a few euros in a sensible cooler from a third party, nothing more stands in the way of OC’s fun. Regular tests in the PC Games hardware, as well as our corresponding purchasing guides in the booklet, will help you with your selection. Current savings tip: The Cooler Master Hyper 412s, which accompanies you on your first steps in the OC for around 25 euros.

So-called tower coolers generally work more effectively and have the advantage of blowing the heat directly out of the housing when mounted accordingly. Top-blowers, on the other hand, swirl the air more inside the housing. Although they depend on one or more case fans for optimum efficiency, they also cool the components surrounding the CPU socket at the same time.

Speaking of CPU: To transfer the heat well to the heat sink, heat-conducting paste or pad are indispensable. Many coolers already have a once-usable order of appropriate material ex-works. Later on, a lot of four dots the size of a pinhead, which is applied to the CPU’s heat spreader like the eyes of a game cube and also at about this distance, proved themselves in practice. The contact pressure of the fastening mechanism ensures a useful distribution.

CPU overclock: The choice of weapons

UEFI or tool of the mainboard manufacturer – this is a frequently asked question, which fortunately can be answered quite easily. Use the options in the UEFI, because after all your PC should also start with the everyday OC without any problems.

The UEFI, the successor of the classic BIOS, which has been established for several years, can usually be reached by pressing the “Del” key directly after switching on the PC. F2 is also frequently represented.

Most UEFIs initially offer a simplified interface, but this is not suitable for OC. Switch to the “Advanced Mode” – usually you can do this using F7, but in many UEFIs you can also set this mode to be called automatically.

Since you’re in the UEFI: Check under the menu item “Monitor” or “Monitoring” whether the radiator installation was successful. The CPU temperature should be only a few degrees above the ambient temperature and in any case below 50 degrees Celsius with the computer just switched on.

CPU overclock: In silence lies the power

Many options can be changed in the UEFI, many of which are for operation outside the specification. The easiest and most promising, but unfortunately also most time-consuming, is to change only one option at a time. For example, the CPU clock multiplier, the memory or system clock or the RAM timings.

For starters, try the multiplier. Although only the C/K and X CPUs at Intel offer a freely upgradeable multiplier, CPUs up to the first Haswell generation (i5-4670/4590, Xeon E3-1230 v3 for example) at least allow the turbo mode to be expanded. With the corresponding option, which Asus calls “Multicore Enhancement” for example, the processor then runs on all cores at the frequency actually only intended for single core load, even under load. That can already bring a few hundred megahertz. However, Intel has put a stop to this option with the Haswell-Refresh. Older Intel CPUs up to and including the first Core-i generation, for example, i5-760, i7-860 or i7-920, however, allow high system clocks and therefore OC values with processors not actually intended for OC. On one of our former test platforms, for example, the i7-920 ran at 175 MHz instead of 133 MHz system clock.

If, on the other hand, your processor has a free multiplier, as all AMD FX processors, as well as the K and Black editions from the same manufacturer, do in addition to the mentioned X and K models at Intel, you can easily tickle out several hundred megahertz additionally. Increase the multi-step by step and start with 300 or 400 additional megahertz – many CPUs already create this value without requiring additional voltage. Try switching off the turbo mode so that the pointless boost values for single core loads, which are actually only beneficial for the better response behavior of lame mobile CPUs, do not dilute your OC successes.

Another important point: Many UEFI versions have “protection circuits” that monitor compliance with the processor’s own TDP limit. The more you overclock, the sooner these functions will intervene and lower the clock again. If you want to get the maximum performance out of your overclocked processor, either switch off functions such as “APM Master Mode” (Asus boards for AM3 processors from AMD) or “Long/Short Duration Package Power Limit” for Intel CPUs or assign them a value which is above the TDP limit of your CPU. But be careful not to enter too high values here. For example, current Socket 1151 CPUs have a maximum TDP of 95 watts (i7-6700K/i5-6600K), which they may exceed for a short time. Don’t allow your CPU more than 120 watts in the beginning and monitor whether the CPU throttles under load with the help of the tool HWMonitor of the CPU-z-makers or Open Hardware Monitor. By the way: No exact temperature is read out for AMD CPUs, even the AMD’s own overdrive tool only specifies a so-called “thermal reserve”, a number of degrees up to the permitted maximum temperature of the processor. Absolute temperature specifications from monitoring tools are therefore always based on an interpretation of this value and can deviate greatly from one another.

In a second step, you can increase the system clock. At Intel, this is currently at 100 MHz and is coupled as a PCI Express and SATA clock, so that instabilities often occur even at 2-3 additional (ergo 102-103) megahertz. With AMD’s AM3 platform, clock increases of 10 percent in system clock (around 220 MHz) are often possible without problems. A further adjustment screw is the integrated northbridge for AMD and the Uncore/L3 clock for Intel CPUs. AMD processors, in particular, can benefit from values of 2.4 or even 2.6 instead of the usual 2.2 GHz. Intel CPUs need one thing above all for high L3 take: a lot of excitement – so get stuck into the core clock first.


On the subject of tension: Their increase carries the greatest risk. Therefore, increase them only in small steps and keep a close eye on the temperature development. But despite all caution: Values above 1.4 volts should not be expected permanently from current processors and from 1.35 volts you should already know exactly what you are doing. Even with good cooling, the processor ages faster with a higher voltage than in normal operation. Although this will not bless the temporal in one or two months, it may only last five years instead of ten. Since many users are now using their CPUs longer and longer, this can already represent a practically relevant restriction!

CPU overclock: Therefore check…

In contrast to some extreme overclocking devices, your overclocking successes should not only lead you to Windows for fast “CPU-Z validation”, but ideally also enable stable operation for everyday use. For a quick, first stability test, for example, Maxon’s Cinebench R15 is suitable; if it runs through without errors, you can take a “real” stability test – or you can take another round of 3DMark as an intermediate step.

For real stability, however, in our experience, real games in long, several-hour game sessions are mainly suitable. 🙂 For this purpose, we like to use Crysis 3, which is very well multi-core optimized in our benchmark scene and often already detects bugs, which leave other games cold.

And another word of warning: Many boards or their UEFI versions mean well with the overclocking user and automatically increase the voltage with increasing multiplier. You should always keep this in mind, but at best prevent it by switching to manual power setting. Soon there are voltages here that we would rather not recommend to the inexperienced user in the long run…

But be careful: With every new game released, new challenges can arise in the form of code sequences. The following applies: “Was stable” does not mean “Is stable”. By the way, this also applies to the combi-OC from different beats: Core, L3, system and memory clock. Stability in individual disciplines does not mean that several, individually stable maximum cycles work together. So if you have balanced the respective limits, go back at least one bar step before combining the bars – in most cases, this will save you a lot of frustration.