It is a pretty basic question, but I could not find an answer to this via Google.
The value you are supposed to adjust is the "voltage offset".
However, there are two kinds of values in the utility that you can both set.
- Core Voltage Offset
- Cache Voltage Offset
Of course, Core Voltage is what you must lower. That is no question.
But should you touch Cache Voltage Offset?
Would it lower the temperature again?
Here is an image of the said options:
And Intel's Extreme Tuning Utility download link.
What is Intel XTU: It's a software that can be installed on Windows 7, 8, 10 and so on.
It gives you the tools to overclock, undervolt your CPU. It also includes a stress benchmark - which I did not find very useful. While it is great for overclocking, you will only meet stability issues later on if you undervolt. That's because the CPU is fine on max P-state - with the lowered voltage, but struggles to stay powered on when running at lower speeds.
Personal experience: Of course I tried it myself, set both to -70mV for example, but I could not notice a big difference, and honestly, the sensor's value is jumping all over the place when it is under load. Like it's 40-50C at idle, then it skyrockets to 70, 80, back to 50. But I see the same trend on my desktop i5/i7 as well.