Would a very large radiator outside at -20F help achieve significant overclocking gains over a more typical 240mm dual loop setup?

Question

I have decided to switch to water cooling my PC. I've got a asus x99 deluxe with an intel i7 5930k CPU, 16 gigs of corsair dominator 2800mhz memory and a nvidia Titan X with an EVGA hybrid water cooling kit.

I live in alaska where our winters tend to get pretty cold. I've wanted to try sticking a car radiator with a fan outside at -20F and hook it into a hybrid dual loop setup like this:

http://imgur.com/a/nMCHq

I understand that the additional complexity and length of tubing may require me to add an additional pump when the large radiator is attached.

If the plan is feasible I would also add insulation to the coolant lines so I would not get condensation from the sub zero coolant lines in the computer sitting inside.

my actual question is: Am I likely to see gains at least 20% beyond what I can do with a typical dual loop setup?

I'm sure the radiator would be able to get the coolant significantly colder from being outside in the freezing cold, but will I be running into other barriers like maximum voltage or clock limitations of the chips themselves that would render the additional cooling redundant?

Thanks

Answer 1

If I could get to 4Ghz with a dual loop. I'd like to see 4.5ghz with the external radiator.

Usual caveats: Overclocking is not an exact science and it's impossible to know for sure.

If you are thermally limited with the existing setup then at -20'f you will almost certainly get 12.5% additional headroom. Of course you have to use a coolant that doesn't freeze at that temperature, which tends to perform slightly worse, but you are more than doubling the temperature difference between the hot and cold sides, so you roughly double the heat dissipation capacity of the system (very approximate thermodynamics). IOW, you will get approximately 100% increase in cooling capacity, or your components can use twice as much power and remain at the same temperature.

CPU power dissipation increases linearly with CPU frequency but quadratically with voltage, so going from 4.0 to 4.5Ghz is a (very approximately) 33% power increase. (see here) Based on math alone, if you were thermally limited to exactly 4.0Ghz, then you should expect about 5.0Ghz with the external loop.

Based on personal experience I would expect you to easily get to 5Ghz+ with an external radiator (given I can get to 5Ghz without one), assuming, again, that cooling is the only factor.

On the other hand, if you are not thermally limited, then it's fairly obvious making it colder won't help. Some processors will not run at 4.5Ghz nomatter how what cooling it has. Some mainboards or power supplies just can't provide enough stable power, sometimes the memory controller borks first. Again, not an exact science - just because you can cool it at 5Ghz doesn't mean it'll actually get there.

Answer 2

I have an ASUS Maximus VIII Hero. It is made for overclocking and has a wizard for overclocking based on what type of cooling system you have. E.g. if you have a large tower heat sink with fans verses a water cooling system. I was honestly surprised because the overclocking difference between a tower heat sink and liquid cooled was minimal.

When the following settings were setup ASUS proceeded to report the percentage of overclocking it could to in order to get the most out of my system.

Scenario 1 Computer USAGE: Gaming Mode Cooling System for Computer:Tower Heat Sink with a Fan ASUS Optimization: Overclocked my system to increase CPU speed by 20%.

Scenario 2 Computer USAGE: Gaming Mode Cooling System for Computer:Liquid cooled ASUS Optimization: Overclocked my system to increase CPU speed by 23%.

Given my motherboard brand is ASUS and they make very good motherboards along with the most impressive BIOS I've ever seen, I'd probably put more trust in that than most.