How to undervolt a CPU on Windows 10

As magical as our computers may be, they don’t work with unicorn kisses and fairy dust. In the end, there is good old electricity coursing through your PC’s electronic veins. Just like any electronic device, the components inside the computer operate at specific voltages. That is, the amount of pressure that pushes electrons through the circuits inside your computer.

Yours CPU it is designed to work at a specific voltage, but you can adjust that number to be higher (over voltage) or lower (undervoltage). It is the last (under voltage of a CPU) that we want to discuss in this article and we will start with the most important question first.

Why undervolt a CPU?

Electronics are not 100% efficient. This means that some of that electrical energy running through your CPU is turned into heat. That’s why your CPU needs a heat sink and fan assembly so it doesn’t overheat. Reducing the voltage of a CPU also reduces the amount of electrons flowing through the system. This translates into less heat.

The first benefit of this is that a cooler CPU will have a longer lifespan. Furthermore, reducing the CPU voltage also means that the CPU will use less power. So, for devices powered by a battery, undervolt can be a way to extend battery life.

Undervolting can also be a way to achieve higher clock speeds in some cases, where high temperatures limit overclocking efforts. However, it is usually overvolting that allows for a overclock stable, so undervolting a CPU is not the preferred method for performance junkies.

Why does undervolting work?

You may be wondering why manufacturers set their CPUs to a certain voltage when they work at a lower one. After all, if the undervolt is that large, why not ship the CPUs at a lower voltage? The answer to this question is that CPUs are slightly different.

Two identical CPUs can have different results at those low voltages. The approved voltage is the one that guarantees operation with the highest percentage of processors. In some cases a certain individual CPU will only really work on the official voltage, but for the most part you will find that you can turn it down at least a little bit with no ill effects.

Is undervolting dangerous?

The answer to the question of whether undervolt is dangerous largely depends on what you consider dangerous or what kind of risks you are comfortable with. Reducing the voltage of a CPU will not damage the CPU or other components. However, it can create system instability, which in turn can lead to data loss. When energized, it is important to test and validate the lower voltage setting before performing any important remote operations with the computer.

Besides the potential for data loss, another real danger when it comes to undervoltage is that yes overvoltages accidentally the CPU. Too much voltage is a quick and effective way to permanently fry a CPU, so make sure 100% to turn the voltage knob in the right direction!

Undervolting via the BIOS

The purest way to reduce the CPU voltage is the BIOS. This is the firmware that makes your computer work before the operating system even kicks into action. Each motherboard has slightly different BIOS menus, names, and steps. So you will need to refer to your motherboard manual to know exactly where to go to change the CPU voltage in the BIOS.

While this is a legitimate way to reduce a CPU’s voltage, using the BIOS can be incredibly tedious. Since after each adjustment it is necessary to start Windows, perform a test and then adjust again. This lengthy validation process is why most people use a software utility to change their voltages.

Keep in mind that if you don’t have a performance-oriented BIOS, there may be no CPU voltage controls to tweak.

Undervoltage of a CPU with a software utility

There are two popular utilities that greedy undervolters use to wean their CPUs off juice. If you are using an Intel CPU then Intel Extreme Tuning Utility (XTU) is a good choice. Nobody knows Intel CPUs better than Intel, after all.

Sadly, the program isn’t the most user-friendly in the world and has a bunch of settings and sections that can get confusing if you’re not familiar with all the CPU jargon. Fortunately for undervolting we only have to worry about a small number of settings. In XTU these are all in the “core” section of the app. What matters is the “core offset voltage”.

Modern CPUs, especially those in laptops, do not use static voltage. Instead, the voltage is adjusted based on the amount of load in the CPU. This is one of the reasons why undervolting is not getting the results it used to, since the CPU is actually undervolting by itself when idle. By adjusting the voltage offset, we change the minimum and maximum voltage range that the CPU will use.

NOTE: If you see that Core Offset Voltage is disabled, this is likely due to a security patch that some Original Equipment Manufacturers (OEMs) have implemented. This primarily affects laptops, but may also be true of some default desktop systems.

This is thanks to a hacking exploit known as Plundervolt. The only way to restore the function would be to flash an unpatched older version of the BIOS, if available. We don’t recommend doing this unless you know exactly what you are doing.

So what about AMD users? We didn’t have an AMD machine to test, but the principle remains the same. The main problem is that XTU doesn’t work with AMD CPUs. The good news is that AMD has its own utility known as Precision Boost Overdrive.

The latest version of the software offers an adaptive undervoltage feature that can have a significant effect on performance, warmth and battery life. So, if you’re using a recent AMD CPU, definitely look into it.

Check the undervoltage settings

With each new voltage setting you need to make sure that everything is still working as expected. There is bound to be a crash or freeze at some point, which is usually an indication that you need to back off a notch or two. But even if everything looks fine, you’ll need to do some thorough work of validating your settings. Here is the sequence of steps we recommend when undervolting a CPU:

1. Before changing anything, run your preferred CPU benchmark and note the score. Take note of your CPU’s maximum temperature. CPU-Z is a great program for this purpose.
2. Reduce the voltage offset by 5 mv. If you are feeling brave you can get an advantage with a 50mv reduction, from there 5-10mv is the most sensible increase.
3. After the reduction, do a stress test such as Prime95 or the stress test built into XTU.
4. Assuming the stress test is successful, run the benchmark again. Performance should be the same or better.
5. Repeat the process.

If your CPU becomes unstable or your performance starts to deteriorate from the previous benchmark, report the voltage to the last successful attempt and use it as the default.

Undervolting is cool, literally

Overclocker and other CPU experts have done a lot for the entire computer industry. Today’s CPUs are very good at overclocking themselves and the same is becoming true of undervolt.

Within a few years there won’t be much to be gained from manually undervolting a CPU, thanks to sophisticated self-tweaking in new CPUs. However, it’s still worth doing on current and past computers. Best of all, the risk is minimal. So why not give it a try?