It is the voltage applied to the CPU cores (the inner workings of the CPU). It varies from chip to chip. The CPU pins will automatically program the motherboard power regulator to provide what the chip needs at stock frequencies.
Too little and the chip will not run reliably. Too much and the chip heats up too much and you can damage the chip. When overclocking, increasing the frequency requires increasing the voltage for stability.
what is CPU voltage and why is important? where does voltage affects? thnx!!!!!!
The CPU voltage is the power supplied to the CPU. Why is it important, because without it your CPU won't have power and won't work. You can control the the voltage using the Bios but this only works on motherboards that allow for overclocking. Most big box computers like HP, Dell, Compaq do not allow for over clocking. You also have to be careful because if you set the voltage to high you can end up frying the CPU.
You know people always say that over clocking creates more heat which is 100 percent true. They then go on to say that that extra heat shortens the life of a CPU but I have yet to see any real proof of that.