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    19th Oct. 2017

How much cooling does your PC really need? How to select the right parts?

Top picture


Generally, if you want a high-powered PC that goes beyond what standard desktop models offer, the best way to go about it is to build a custom one. This allows for future upgrades, and you can invest in specific components that can satisfy your needs. You also don't have to worry about your machine becoming obsolete because you can always upgrade individual components for more power on the right spot.

 

However, you do have to know what you're doing! If you are playing with high-performance components, you have to take some parameters into account to get the optimal combination. For example the power dissipation. The more powerful your PC is, the more heat it will generate, so you have to take care about that. But how do you choose the right cooling solution for your PC? There are many types of cooling parts and configurations on the market. So, let's go over which one may be right for you.

 

CPU Cooler

The processor may be the most important part of your rig. When you choose a CPU (not OEM) then you get a stock cooler too. If you have very good airflow in your case and you don't want to overclock your processor and if you won't stress your gear for a longer duration than it may be suitable for your needs. But for a stronger build, I definitely recommend getting a 3rd party cooler. The socket of your CPU can determine the type of the cooler (because of the socket) but there are a lot of coolers that are compatible with multiple socket types. For example Dark Rock Pro 3. This is a good point because you can use it in the future for CPUs with different sockets.

Notice that in case of large coolers like Dark Rock Pro 3 you should compare its sizes with your case's dimensions. It won't fit in average cases.

 

Thermal Power

If you have a look at the specs of the previously linked cooler, you can see this: "TDP: 250W". No! This isn't the power consumption of the fans. This is the maximal recommended TDP for the CPU cooled by Dark Rock Pro 3. CPU-World defines thermal design power (TDP) as the maximum amount of heat that a semiconductor (here the CPU) dissipates as it works. The higher the TDP, the more work your fan needs to do dissipating that heat. So looking at your processor's TDP can help you to select a properly sized cooler. Of course, always look at some reviews and test results about the selected part.

 

GPU Cooling

GPU's cooling is very different from CPU's. In most cases, if you replace the stock cooler on your graphics card you will void warranty. So the almost only situation when this does worth it when you build a custom water cooling circuit including multiple components of your computer. If you go this way then you can get the sum of power dissipations and calculate the right size of radiators. Otherwise, use the stock cooling.

 

HDD, RAM, SB, other components...

RAM cooling picture

If you do serious overclocking, then you may need RAM and southbridge cooling. But on these levels of OC, you may already have a custom water cooling system installed. For a general build even designed for gaming or audiovisual work, you won't need any kind of extra HDD, SSD, ODD, RAM or SB cooling.

 

Case Airflow

To get the max performance out of the component coolers you will have to provide them cool air what they can use for heat exchange. For air coolers and for the radiators of a water cooling system too. Let's use a little bit of physics to determine the optimal set. At first: the cool air tries to get down. At second: when you build up your fans you should calculate with the pressure difference in front of and behind the blades.

Case cooling picture

Quick conclusion:

1. Put your inhaling fans to the lower places and the exhaling ones in the higher slots.
2. Get a bit more inhaling power than exhaling.
3. Don't put on fans in the opposite directions! Vortex can harm airflow.

 

Fan Properties

If you look at a fan's specs you will see a lot of parameters:

Fan specs table

The most important ones are the Airflow, Static Pressure, Noise, Size, Bearings and Connector.

In case of PC fans, the voltage is almost always 12V, so you don't have to bother it. The power consumption is also very low, so we can ignore that too.

Airflow: Volume of the air what the fan can blow in a specified time. m3/h means 1 m3 as volume and 1 hour as time.

Static Pressure: Static pressure depends on the shape and the angle of blades (and RPM + Size of course). Fans with high static pressure are optimized to be used on heatsinks/radiators because they can squeeze the air through the plates. Fans with smaller static pressure (so higher airflow) are better to use as case fans.

Noise: Level of the noise generated by the spinning fan. This can be exactly measured and you can find comparison tables on the internet like this one:

Sound level comparison table

Size: The larger the fan is, the higher its airflow/static pressure is at the same RPM. So if you use bigger fans, your build can be more silent. It's recommended to utilize the maximal fan size on your case/heatsinks.

Bearings: The joint type of spinning parts of the fan. It can affect the lifetime. Some poor bearings can get loud after a time of using.

Connector: There are 4 main types of it: 2pin, 3pin, 4pin and molex.
The first 3 can be connected to the motherboard pin headers.
The 2pin version get's the power and doesn't give any feedback. It can be controlled by for example PWM or constant voltage level, but you won't know its RPM.
The 3pin version is similar but on the 3rd pin, it gives feedback about its speed. Every rotation generates a signal on that pin so mobo can determine its RPM.
The 4pin fans work just like the 3 pin fans, but on the 4th, pin they get an extra control signal. They can be controlled by PWM on the first 2 pins and/or with the extra signal. For professional control, you don't have to use 4pin fans (although a lot of source says this) if you have a controller with constant voltage or a PWM controller fast enough to avoid the clicking sound. Of course, if you always spin your fans at 100% then the 3rd and 4th pins are completely unnecessary.
The molex connector can be connected directly to your power supply or with an adapter to the mobo. Fans with this type of connector can be controlled like the 2pin ones.

 

Case cooling picture

Fan/Water cooling Control

Yes, "Water cooling Control". Because water cooling systems have active parts which can be controlled too to get the lowest sound level and power consumption. Another thing about fan control is the famous thought of "Why would I need fan control? I can put on my headphones and I can't hear the fans." Why? Because I don't put a clip on my nose when my armpit stinks. Keeping the headphones always on your ears is just an uncomfortable way of escape.

What kind of controller should we use?

Software: There is some fan controller software that can control the fans connected to the inner ports of your PC (eg. Motherboard, Video card). This means small number of fan ports and low load capacity on them. Most of these software controllers aren't too smart, but you should definitely try the SW part of Feverkill. It's easy to use and provides professional control settings.

Hardware: The analog solutions with a few potentiometers don't deserve the "controller" name. The digital ones are better but they also can't query the temps from the built-in (CPU, GPU, HDD, etc...) sensors and can't control the fans on the inner (Mobo, etc...) ports.

Combined: The only one on the market is Feverkill. An automated, complex but easy to use SW+HW tool with event-based overheating protection and lots of monitoring functions. The SW on the PC can manage an optional USB hardware to use more devices: sensors, fans, pumps or LEDs if your mobo doesn't have enough ports for them. A unified tool for advanced fan control and protection. (Check the menu at the top of the page!)

 

Thermal Paste

Using a good thermal paste is very important! Actually, it's much more important than you would think. There are a bunch of properties that describe a thermal paste, for example, viscosity, metal content, time to dry, etc... but what most influences the thermal conduction is that mysterious W/(mK) value. If you are in the know of some physics, you can calculate exact values for exact components but I can tell you, that the 1-2W/mK pastes are only suitable for smaller amplifiers. What you should use is, for example, this one. 8.5W/mK.

This paste is very gluey. If you buy this one, be very careful when you remove the heatsink from your CPU. It's actually able to pull the processor out of the socket even if you didn't open it before! (Yeah, personal experience.)

 

Case cooling picture

Measurement

If you are an engineer too, this point is evident for you. We always check what we've done. The main point: Is the cooling capacity high enough to keep the temps at a suitable level during continuous load? To test this, we maximally charge our gear and watch the thermometers.
For CPU, the best stress test tool is Prime95. You can use for example FurMark for GPU. Run both at the same time to get the maximal heat out of your rig!
If the temps are suitable, then your setup has proper cooling... for the current ambient temperature. Sadly, in the summer it's harder to cool a computer. You can decide if it's silent enough for you. If not... change!
In case of one of your hardware in the PC is hotter than it should be, you can try to change the flow with your case fans before you buy something new for that specific hardware.

 

We wish you happy building, high clocks and low temperatures!

Average: 95%