How to Choose and Mount a CPU Fan: Everything You Need To Know
Are you looking to mount a new CPU fan? Finding the right CPU fan requires a great deal of research. Not only do different fan sizes populate the market, a byzantine maze of CPU socket types, bearing technologies, fan speeds and more greatly complicate the selection process. Fortunately, you’ve come to the right place.
This how-to guide explains the nitty-gritty of getting the right fan and mounting it to your PC’s CPU. Additionally, it explains my favorite method for applying thermal compound to a CPU.
If you’re simply looking for installation instructions on how to mount a CPU fan, skip to the second part of this article.
What Kind of CPU Fan Do You Need?
The PC component that keeps your CPU cool consists of two separate parts – the heat sink, which is typically a block of metal, designed to maximize airflow and surface area. The second part is the fan. Together they’re commonly referred to as the heat-sink/fan combo or HSF, for short. Lots of technologies and aftermarket products exist. Some are designed to reduce noise while others are designed for maximum cooling. All of them, however, require you know a few things about your computer.
Determining what sort of CPU fan you need takes five steps.
- First, find your motherboard’s CPU socket.
- Second, measure the available height in your case between the top of the CPU and the panel of the computer’s chassis.
- Third, inspect the area on your motherboard surrounding the CPU socket.
- Fourth, determine how fast you want the fan to run.
- Fifth, find the Thermal Design Power (TDP) of your CPU, if you are not using the stock (the one that comes with the CPU) HSF combo. TDP is the heat output of your CPU, measured in watts.
Step one, get the socket type: There’s a variety of CPU sockets out there. Fortunately, the vast majority of modern CPUs fall into one of three kinds:
- Intel LGA775: Unfortunately, Intel heat-sink/fan combos differ across generations. If you have a LGA775 socket CPU, it will require either an LGA775 compatible Intel heat-sink/fan combo, or a complicated “universal” after-market HSF. An exception to this rule is the transition between LGA775 and LGA1155. You can also use LGA1155 heat sinks on LGA775, although there may be some compatibility issues, particularly with bracketed coolers.
- Intel LGA1155: In general, Intel did not rationalize its fan design. Intel tends to use a different heat sink for each of its CPUs. However LGA775 and LGA1155 HSFs are mostly cross-compatible. The new Haswell LGA1150 socket appears to also work with LGA1155 and LGA11775 sockets.
- AMD AM2, AM2+, AM3, AM3+, FM1 and FM2: Conveniently, almost all modern AMD socket types use interchangeable CPU heat-sink/fans. If you have one of these AMD models, almost all heat sink/fans work interchangeably, provided they can handle the heat produced by the CPU.
Remember these issues, because there’s a big difference between the way you would apply a heat-sink/fan to AMD or Intel CPUs.
Step two, measure your chassis height: Some CPU fans can be too tall for your case, particularly if you have a small form factor PC build, such as mini-ITX or microATX. Be sure to measure from the base of the CPU to the top of your case.
Step three, check your motherboard: Some motherboards arrange a great number of components around the CPU, which make mounting anything other than the stock cooler impossible. Measure the radius surrounding the CPU to the nearest capacitor or other component. heat-sink/fan combos will not fit if they exceed this distance.
Step four, determine your fan’s speed: Some motherboards only use a three-pin CPU fan connector (clearly labeled CPU fan), meaning it isn’t fed Pulse-width modulation (PWM) commands, which modulate the fan’s speed in relation to the temperature of the motherboard. Most three-pin boards run fans at their maximum rated speed. Logically, a three-pin CPU fan is designed to run at maximum speed, since it has no fourth pin. However, it should be noted that some motherboards can control a three-pin fan through a native voltage control method.
Step five, find your CPU’s TDP: As mentioned above, fans have TDP ratings, measured in watts. This is the maximum amount of heat that the fan can successfully vent from a CPU. The heat-sink/fan combo should meet or exceed the TDP of your CPU.
How To Mount the CPU Fan
Mounting the fan is a three part process: First, inspect the heat-sink/fan. Second, if you don’t have thermal paste preapplied to the heat-sink/fan combination, you will need to apply it. Third, attach the heat-sink/fan to the CPU. Many of these steps will feel familiar to someone who has extensively modded their computers . However, even veteran builders might learn some useful tips from a review.
Step one, examine the size and shape of the heat-sink/fan. If you’re not certain it will fit, you may want to carefully measure it so that length of the heat-sink/fan’s power connector will reach its corresponding connector on the motherboard. If you don’t, you may find yourself remounting the HSF, after rubbing off its thermal paste.
Step two, if you don’t have thermal paste already applied to your heat sink, you will need to add it. Application requires several steps:
- Prime the heat sink and CPU surfaces: If you were to take an electron microscope and examine the surfaces of the heat sink and CPU, it would appear as an alien planet, filled with valleys and craters. You can prime each surface with thermal compound, which fills in these valleys with thermally conductive material, enhancing the flow of heat. To do so, take a microfiber cloth or coffee filter, and apply a tiny amount of thermal paste to each surface and rub until it feels smooth.
- Apply the thermal compound in one of four basic patterns, depending on the CPU: Either (1) a vertical line, (2) a horizontal line, (3) covering the surface or (4) a rice-sized dot in the center of the CPU. For more information on how-to apply thermal compound, check out Arctic Silver’s brilliant application guide. Personally, I always use a dot, regardless of the CPU type.
- Keep the following tips in mind: If reusing an older heat sink, remove the thermal paste on the CPU and the heat sink using 90%+ alcohol solutions. Apply the alcohol to a lint-free wipe and use this to remove the thermal compound. I prefer using denatured alcohol, although I’ve been told that the bitumen residue may lead to undesirable side-effects (in my experience, it has not).
- Metal-ion thermal pastes are also electrically conductive. If you accidentally apply it to your hands and then touch the motherboard, you may cause a fatal short. Therefore, when applying such a compound, keep your hands clean and exercise extreme caution.
- Don’t apply too much thermal paste. After pressing the heat sink into the top of the CPU, it will cause the paste to spread out. A little goes a long way. Typically applying a dot the size of a grain of rice is sufficient.
Step three, attach the heat sink:
On stock Intel heat-sink/fans, the push-pin attachment style leaves a great deal to be desired. Optimally, it’s best applied before you screw the motherboard into the PC chassis. If this isn’t an option, you take the risk of damaging your board. Fortunately, many aftermarket Intel HSF use push-pins that actually work. There’s also back plate-equipped alternatives that dispense with the pins mechanism, pictured below.
To get started:
- Position your heat-sink/fan so that its pins line up with the four holes in the motherboard.
- Make sure you have a long enough power connector to reach from the fan to the male port on the motherboard. This will clearly be labeled as “CPU Fan” and will have either three or four prongs.
- Make sure the thumb-grips on the top portion of the push-pins are in the locked position. If they are not, twist the thumb-grip in clock-wise fashion until it stops turning. Pictured below is an image of a thumb-grip in the locked position.
- Push any one push-pin through the hole in the motherboard until a clicking sound is heard. Make sure that the black central pin has fully extended. You may want to wiggle the pin from side-to-side, first, before doing so. I find that giving each one of the tips of the push pins a small coating of mineral oil (non-conductive) aids substantially in successfully pushing the pins through the board. Once fully extended, the central spike will protrude, as shown below.
- Move to the push-pin that’s diagonal from the one that just got pushed through. Push it through.
- Push through the remaining two push-pins. The very last pin will take a bit more force to successfully push through.
- Once completed, try wiggling the heat sink slightly. If it wiggles under pressure, go through the process again. A loose HSF may cause your computer to overheat.
AMD heat-sink/fans clip onto the motherboard, as opposed to the awful the push-pin arrangement. This method offers the easiest and most error-free way of attaching a CPU cooler. AMD CPUs have the distinct advantage of ease of installation and a total lower cost of ownership, since you can reuse heat sinks on later builds. To attach your AMD heat sink:
- Simply place the heat-sink/fan over the CPU.
- Notice the thin metal bar going through the center of the heat sink? First hook that bar through the protrusion from the motherboard, without the handle.
- Next, hook the other end (with the black handle on it) over the protrusion on the other side.
- Finally, pull the lever in a circular motion, 180 degrees. This locks the HSF into place.
Out of the two, I prefer AMD heat sinks because they are tremendously easy to use. Intel’s, on the other hand, don’t mount as advertised. I’ve spent many hours fiddling with getting the Intel HSF snugly fitted to the board because I refuse to detach my motherboard every time I decide to work on the fan. As someone who has built and rebuilt computers countless times, Intel push-pins give me nightmares.
Picking the right heat-sink/fan combo for your computer is easy – just find the socket, measure your case and find the TDP of your CPU. Installing it is just as easy – apply thermal compound and attach the heat-sink/fan.
For additional tips on how-to keep your computer running cool, check out my article . It covers several alternative computer cooling tips, such as installing a dust filter, properly greasing squeaky fans and more. For those of you with laptops, considering some MacGuyver-like tricks for keeping your PC cool, on the cheap.
Anyone else love installing heat sinks-fan combos on their rigs? Let us know in the comments.