Overclocking study – Intel Core i7 4790K & Intel Pentium G3258 – air, water, phase-change, DICE & LN2
Ok, in order to achieve a nice looking clock speed you need an unlocked CPU, an overclocker friendly motherboard and a good quality power supply, among other things. But one of the most important aspect of overclocking is cooling the components we want to overclock, in this case the CPU. Because higher frequency and voltage will always mean higher temperatures. Don’t get me wrong, the CPU’s have their internal protection mechanism that will always lower the voltage or even shut the system down before anything happens to you CPU.
So it’s not a “oh my gosh, I am afraid I will burn my CPU” situation, but if we want to reach system stability, or the highest clock possible, the temperature will eventually stop us. When we are looking for stability, it will stop us because eventually the CPU will go into throttle at one point, that means that not all cores will be active and the speed we set will no longer be applied, so the performance will drop. When we are looking for the highest clock speed temperature will also stop us after a point, and we will need a different type of cooling in order to apply higher voltages and get higher clocks.
Well, the first type of cooling we are going to use when we overclock is obviously air-cooling. Simply by switching the flimsy stock cooler with an aftermarket beast, like Noctua NH-D14, will get you more MHz. Using a good quality thermal interface material and some strong fans will also get us extra MHz.
Any type of PC component cooling is based on a simple principle – heat exchange between the thing we are trying to cool (CPU) and what we use to cool it (cooler). Air cooling principles haven’t changed in a while – you apply TIM on the CPU in order to maximize the heat transfer then you use a cooler with a good mounting system and a good quality base to take the heat from the CPU and use the cooling agent to keep the CPU temperature down. In the case of air cooling, the cooling agent is air. And the performance of our cooler depends on the temperature in the room – the ambient temperature. Basically you can only cool your CPU down to the temperature of your room (at most).
The first CPU’s didn’t even need a cooler, then a small aluminum or copper radiator was placed on the CPU to dissipate the heat into the air, then a fan was added to help with this process. With time coolers got bigger and bigger, in order to keep up with the power consumption of the newer CPU’s, and after a while the heatpipe was invented. Now the base of the cooler would take away the heat from the CPU, the heatpipes would transport it to the fins, and the fans would help with the heat exchange between the surrounding air and the fins. The cooling agent in the heatpipes would get cooler, it would go down to the base, realize the thermal exchange with the CPU and then the whole process would be repeated.
As we already mentioned, all our tests (except the low ambient one) were done in the same conditions – 25 oC ambient temperature. We used one of the best air coolers out-there (Noctua NH-D14), together with a good quality TIM (Arctic Cooling MX-4) and two fans (Coolink SwiF2 120P) that can get up to 2000 rpm. This is the situation most relevant for a person that wants to find the best clocks for daily use, with a retail cooler and some fans that don’t blow your ears away.
The next step was the low ambient air-cooling – we lowered the ambient temperature to 17-18 oC, we switched the fans for some 5400 rpm monsters and we gave it another try.