Why does a processor overclock faster when cooled with liquid nitrogen? Also, is the inverse the reason why the processor slows down when it get's hot?
I'm specifically interested in Intel processors.
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.
Sign up to join this communityIt's not the temperature that makes it run faster or slower. The lower temperature allows more heat power to be removed from the device, which allows more electrical power to be put in without burning it up, which allows it to be clocked faster. Part of the electrical power required is proportional to the clock speed.
You want to keep the core within its operational range. If you want to run the core faster which means it consumes more heat/energy then you need to remove more heat to keep it within its operational temperature range. If you can improve the cooling through various methods, fans, liquid, gas, otherwise, then you can add more energy in the form of an increased clock (multiplier). You can damage the part by trying to run it too cold as well as you can by running it too hot. Also there is a physical limit to this you cannot run it infinitely fast infinitely cold. Your limit is likely determined by the silicon itself, there is a limit to the clock multiplier, and you would have to change the reference oscillator to keep increasing the clock rate.
Think about the human body, try running a mile when it is 60 degrees outside, then find a place to try running in the same clothes when it is 110 or 120 degrees outside. Which one are you likely to make it through the mile without passing out (failing)? Which temperature will allow you to push yourself harder than normal? Keep your body within the operating temperature range and you can push it harder, at least for a period of time. If you warmed up inside before the run, you might push yourself a little faster if it were 50 degrees outside. But there is a limit, warm up all you want indoors, but in a t-shirt and shorts, you may not make it when it is 30 below outside, 40 below, 50 below.
Several folks have correctly answered that more cooling allows the CPU to run faster, BECAUSE if it is cooled it allows you to overclock it more. These same folks correctly implied what I am about to say plainly: This was not (until recently) a native talent of CPUs. And it never has been a physical law of semiconductors.
A CPU clocked at 1.2 GHz runs at exactly 1.2 GHZ, whether it is cooled to 60F or running at 160F. If you lose cooling (e.g., remove the cooling fan + heat sink), it will run at 1.2GHz until it melts itself into a puddle and can no longer run at any speed. But it will run at exactly 1.2GHz until the very second it dies. I'll bet many on this forum have actually witnessed/experienced this.
Some of the new-fangled computers have their own temperature monitoring and control systems which automatically enable/disable overclocking (or otherwise adjust CPU speed) based on CPU temperature. So if the CPU gets too hot, it slows itself down (reducing energy in) rather than burning itself up. (I reckon it does this by selecting a slower clock or by dividing the existing clock down; but I am not an expert on newer CPU innards.)
If the CPU cools down, the automatic governer circuitry reverses this process to allow the CPU to run faster.
Just to clarify: It's not about just heat dissipation. You can dissipate 1000 W of power using boring water cooling, but it would not allow you to get to the top.
The idea is that property of semiconductors change, as well as resistance of interconnect (=copper). Lower resistance - lower RC constant, which is main factor limiting processor speed.
If one could cool it down to superconductivity stage, clock would increase even more - but this is unlikely for copper interconnect we see in current CPUs.
Semiconductors run faster at a lower temperature and at a higher power supply voltage. Higher voltage means more heat generated, which means that it has to be cooled more. The more you can cool a chip, the faster you can make it go.