How To Choose A CPU Cooler

Any electrical circuit has resistance, and electrical resistance is the principle upon which both CPUs and toasters are designed. Electrical semiconductors have the unusual trait of being able to switch between low and high resistance when electrical current is applied in a certain way, and those states represent the 1s and 0s of a logic circuit. Although the logic circuits of a CPU are not intended to create heat, those principles mean that we’re all running little tiny hotplates in our machines.

Data processing is the added benefit of designing your toaster as group of logic circuits, but how do we prevent the little chunks of glass upon which those circuits are etched from melting into a toasted lump? A chunk of metal designed to draw heat away from another object is called a sink, and that’s what’s at the core of CPU cooling.

Yet the name “heat sink” really doesn’t mean much, because a sink is simply something that absorbs heat. More than simple sinks, a large surface area of fins helps CPU coolers transfer heat to a greater volume of comparatively cool air. Those fins make a standard CPU heat sink a type of radiator, in spite of the nomenclature. And like most radiators, convection is a more significant cooling force than radiation, as the rising of warm air causes cool air from beneath to take its place.

Heat is proportional to things like clock frequency, circuit voltage, circuit complexity and the material upon which the circuit is engraved. While a few low-energy CPUs can be cooled using nothing more than a set of fins, most desktop users want more performance, which comes at the cost of more energy (heat) to dissipate.

When natural convection doesn’t replace warm air with cool air fast enough, forced convection is accomplished by adding a fan. The above image shows a rare all-copper cooler, which relies on the principle that copper transfers heat faster than aluminum. It also weighs and costs more than aluminum. Manufacturers often surround a copper pillar with aluminum fins in order to achieve better cooling-to-cost and cooling-to-weight ratios.

More fans and more surface area give a CPU cooler even greater capacity. Liquid cooling allows enormous radiators that wouldn’t fit over the motherboard to instead be mounted to a panel on the case. The CPU is topped with a component called a water block, which transfers heat to the liquid. A pump, seen mounted on the side of the radiator depicted above moves water (or coolant) through a series of channels on the radiator and water block.

While any of these solutions maximize contact with moving air, none would work well if the CPU were not making contact with the cooling apparatus. Thermal interface material fills the gaps between the top of the CPU package, eliminating the trapped air that would otherwise act as an insulator. Most CPU coolers ship with some type of thermal interface material, and many coolers come with that material factory-applied to the mating surface. Performance enthusiasts often seek out better-performing products to replace the cooler manufacturer’s solution, although the difference between various products designed for the task is usually quite small.

Compressor units are on the extreme end of the complexity curve, using refrigerant to produce CPU core temperatures far below ambient conditions. These generally use far more energy than the processor does, and can scale up to designs that compress and cool air in several stages to produce a liquid-nitrogen drip. Condensation around cold components becomes a big concern, so that even the simplest “refrigerator” designs are generally used just for exhibition purposes.

Of course the Bigger Is Better rule is limited by case size, but there are a few other factors to consider. Since this is a beginner’s article, we’ll cover the range of coolers that make up our Best CPU Cooling awards showcase. These include Big Air coolers over 6” tall, Slim designs that are under 3” tall, Mid-Sized coolers from three to six inches tall, and pre-filled liquid cooling kits.

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  • redgarl
    Blower GPU have worst quality coolers and provide lower OC capabilities. Not only that, but throttle and offer less stability... and are noisier...

    The only reason to buy one is because you overlooked the importance of a good case, and especially if you are planning on multi-gpu setups.

    I can only disagree with the writer finding open-air cooler defective. Best example in the news, the 1080GTX FE.
    9
  • Mopar63
    Thomas, I actually did an entire set of experiments to see if, in the majority of scenarios, an open air cooler (which you said was defected) created any problems compared to a blower cooler.

    In my research any computer case with a good air flow design can easily handle an open air cooler. During my testing under full system load the internal air temperature of the case only raised about 3C with an open air cooler. Now if we assume a blower cooler is 100% efficient at removing the heat from the case then in this scenario the difference with internal temps would only be 3C.

    Now what do we get for that 3C increase in overall case temp? Well we see a pretty good reduction in GPU temp overall, plus we see much lower noise levels.

    That 3C BTW translated into a 3C increase of various motherboard components and no increase in CPU temps. What does this mean? Nothing as 3C is within margin of error and can be effected as much by ambient room temp and anything done with the cases air flow.

    Your premise that open air coolers are "defective" is false.
    9
  • badirontree
    Most people prefer a cool GPU because in games you never use 100% of the cpu all the times... So it never gets hot to be a problem....
    3
  • DonkeyOatie
    Horizontal motherboards and cube cases mitigate much of the mechanical issues of 'big air'. I have a Noctua D15S on a mATX board in a Thermaltake X21 case with a 4.6+ Ghz i7 4790K that is used for Science Fair projects and gets moved around a lot. I was prepared to replace the motherboard and go to liquid cooling, but the system has done well so far with middle school students handling it. They are trained to be careful (break it and you bought it).
    1
  • Crashman
    Anonymous said:
    Blower GPU have worst quality coolers and provide lower OC capabilities. Not only that, but throttle and offer less stability... and are noisier...

    The only reason to buy one is because you overlooked the importance of a good case, and especially if you are planning on multi-gpu setups.

    I can only disagree with the writer finding open-air cooler defective. Best example in the news, the 1080GTX FE.
    Disagreeing doesn't make you right though. Nvidia put a bunch of effort into its top blower cooler and it worked very well. Dumping that heat into your case isn't simply a bad idea, it's the kind of idea that makes me question your judgement on just about anything. And getting five upvotes from people with equally poor judgement isn't going to change my analysis.

    Anonymous said:
    Thomas, I actually did an entire set of experiments to see if, in the majority of scenarios, an open air cooler (which you said was defected) created any problems compared to a blower cooler.

    In my research any computer case with a good air flow design can easily handle an open air cooler. During my testing under full system load the internal air temperature of the case only raised about 3C with an open air cooler. Now if we assume a blower cooler is 100% efficient at removing the heat from the case then in this scenario the difference with internal temps would only be 3C.

    Now what do we get for that 3C increase in overall case temp? Well we see a pretty good reduction in GPU temp overall, plus we see much lower noise levels.

    That 3C BTW translated into a 3C increase of various motherboard components and no increase in CPU temps. What does this mean? Nothing as 3C is within margin of error and can be effected as much by ambient room temp and anything done with the cases air flow.

    Your premise that open air coolers are "defective" is false.
    You're implication is that a case should be made noisier to remove GPU heat, and use a quieter GPU cooler to compensate. But if you blow the heat out the back, the extra noise can be taken care of by a case with fewer, more strategically located vents. And the 3C difference meant something to me in the SBM series :D
    -6
  • Dunzaus
    Praising liquid cooling as much as you so is misleading. You talk about what can happen with a big air cooler ( if it get shipped =/ or mishandled ) , but you don't care to mention what will happen if your liquid cooling system starts leaking water.

    I'm sticking to air cooling, because I have seen too many youtubers that really knows what they are doing with computers, like linustechtips, and still having leaks.
    0
  • bit_user
    I like downdraft coolers, for their added cooling of VRM (when it was separate), RAM, and chipset. A good downdraft cooler can easily handle a 130 TDP CPU.

    As for radiator placement, I think the best location would be to exhaust out the side, near the bottom. That way, it gets cool air and can run the fan slowly. This would allow hot air still to be exhausted near the top of the case.
    0
  • Crashman
    Anonymous said:
    Praising liquid cooling as much as you so is misleading. You talk about what can happen with a big air cooler ( if it get shipped =/ or mishandled ) , but you don't care to mention what will happen if your liquid cooling system starts leaking water.

    I'm sticking to air cooling, because I have seen too many youtubers that really knows what they are doing with computers, like linustechtips, and still having leaks.
    We haven't, at least not visible leaks. Our leakage problem has been microscopic leaks that cause a cooler to dry out after around three years. We recommend air coolers for most stationary systems.
    0
  • bit_user
    Anonymous said:
    Anonymous said:
    Blower GPU have worst quality coolers and provide lower OC capabilities. Not only that, but throttle and offer less stability... and are noisier...

    The only reason to buy one is because you overlooked the importance of a good case, and especially if you are planning on multi-gpu setups.

    I can only disagree with the writer finding open-air cooler defective. Best example in the news, the 1080GTX FE.
    Disagreeing doesn't make you right though. Nvidia put a bunch of effort into its top blower cooler and it worked very well. Dumping that heat into your case isn't simply a bad idea, it's the kind of idea that makes me question your judgement on just about anything. And getting five upvotes from people with equally poor judgement isn't going to change my analysis.
    Wow, self-righteous much?

    Just look at the industry. If blowers were the ideal solution for cooling on air, why isn't everyone using them, especially in the higher-end cards? Maybe you think all the OEMs building graphics cards are idiots and can't learn from their decades of experience?

    What if Nvidia only uses blowers as a safe bet - to mitigate against people with poor case circulation - as redgarl mentioned? Or maybe because they're cheaper, having only 1 fan, and Nvidia is content to let their OEMs worry about more elaborate cooling solutions that allow the GPU to stretch is legs?

    Blowers have one disadvantage I haven't seen mentioned, which is negative pressure. By exhausting out the back, they suck a lot of dust into your case, especially if you have a multi-GPU setup. The way to combat this is with dust filters and positive pressure, but the blowers mean you need high intake CFMs, which will turn your PC into an absolute wind tunnel and clog your dust filters very quickly.

    I agree with Mopar63's conclusion, which is that open air cooling doesn't raise case temps much, and case temps aren't really a limiting factor for anything. So, while it seems less elegant than to exhaust the waste heat, it is an exercise in optimizing the limiting factor, which is nearly always GPU temps. So, it works out that if you're not going with water cooling, your best bet is open air and decent case airflow.

    Normally, I prefer rational argument to downvotes, but your tone has earned you my downvote. As a site staff member, you might think more about how to interact with readers. You are in a privileged position of controlling what's in the article, so if people disagree with you, there's no need to get nasty. All of the other writers I've seen comment in the forums seem to understand this.
    2
  • redgarl
    Anonymous said:
    Anonymous said:
    Blower GPU have worst quality coolers and provide lower OC capabilities. Not only that, but throttle and offer less stability... and are noisier...

    The only reason to buy one is because you overlooked the importance of a good case, and especially if you are planning on multi-gpu setups.

    I can only disagree with the writer finding open-air cooler defective. Best example in the news, the 1080GTX FE.
    Disagreeing doesn't make you right though. Nvidia put a bunch of effort into its top blower cooler and it worked very well. Dumping that heat into your case isn't simply a bad idea, it's the kind of idea that makes me question your judgement on just about anything. And getting five upvotes from people with equally poor judgement isn't going to change my analysis.



    Arhmm... first off dumping air in your case isn't really a matter if, like me, you have a Fractal Design R2 XL with optimal airflow + a fan controller. I removed my HDD cage and put all my storage in my 5.25 bays. Also, I am having 7 fans exhausting heat from front to rear and bottom to top + a side fan for my CF setup.

    Now for graphic cards... the 1080 GTX FE throttle when the temps are getting too high. A simple OC is resulting in worst performance however not with the open-air cooler. Gigabyte is having a card with 170 MHz OC off the bat and temps of about 20C less.

    Finally, what is going to make your system crash, is your GPU temp over anything else. So investing in an open-air cooler make sense, not the other way around. Blowers are used because they are cheaper and were the first type of proven coolers, that's it.
    1
  • lordmogul
    Anonymous said:
    Thomas, I actually did an entire set of experiments to see if, in the majority of scenarios, an open air cooler (which you said was defected) created any problems compared to a blower cooler.

    In my research any computer case with a good air flow design can easily handle an open air cooler. During my testing under full system load the internal air temperature of the case only raised about 3C with an open air cooler. Now if we assume a blower cooler is 100% efficient at removing the heat from the case then in this scenario the difference with internal temps would only be 3C.

    Now what do we get for that 3C increase in overall case temp? Well we see a pretty good reduction in GPU temp overall, plus we see much lower noise levels.

    That 3C BTW translated into a 3C increase of various motherboard components and no increase in CPU temps. What does this mean? Nothing as 3C is within margin of error and can be effected as much by ambient room temp and anything done with the cases air flow.

    Your premise that open air coolers are "defective" is false.


    3°C on the graphics card can be the difference between archiving the maximum boost speed and a reduced clock if these 3°C fall into the threshold.
    Besides that it's nothing to be concerned about even though some people try to convince others that it might be the difference between life and death.
    0
  • none12345
    Im going to also disagree about the open air coolers being defective.

    I personally do not care about dumping heat in the case, i want the GPU as cold as it can be, as its usually the bottle neck.

    Of course i also dont run with a closed case under a desk either. Its open sided with nothing next to it, so dump away!

    I really dont care if its a blower or open air cooler tho. Whatever cooler gives better thermals with better acustics wins. Simple as that.
    1
  • Sam Hain
    I disagree with the portion of the article, referring to top-mounted radiators; "... and radiators placed there usually work best with the fans underneath, blowing upward."

    Pulling cool-air in from outside the case over the rad has advantages that outweigh drawing hot-air from inside of the case through it

    - Lower CPU temp achieved due to COOL air being supplied
    - Acts as another "intake" source of COOL air for your rig, where as your front intake
    fan may not be able to reach
    - Depending on case design, acting as an intake may prove to be better for intake-to-
    exhaust air flow

    In my xp with closed-loop coolers, this has always been the case with top-mounting. Others may have had different results with exhaust setups but I'd be surprised if so...
    -
    0
  • turkey3_scratch
    Just one thing I'd like to point out, in the very introduction you state "Electrical semiconductors have the unusual trait of being able to switch between low and high resistance when electrical current is applied in a certain way", however, it is not the current that is applied but it is the voltage.
    http://amasci.com/amateur/transis.html
    Quote:

    To turn on an NPN transistor, a voltage is applied across the base and emitter terminals. The base current is not important to transistor operation. It's just a byproduct of the REAL operation, which involves an insulating layer called the Depletion Region. By focusing attention on the current in the Base lead, most authors go up a dead end in their explanations. To avoid this fate, we must start out by ignoring the base current. Instead we look elsewhere for understanding.
    0
  • TJ Hooker
    @turkey3_scratch FYI that article is talking about bipolar junction transistors (BJT). Most modern digital ICs, like CPUs, use field effect transistors (FET). That being said, FETs are also voltage controlled devices. However, turning a FET on or off involves charging/discharging the gate capacitance (through applying a voltage), which one could argue constitutes "electrical current applied in a certain way".

    As an aside, after skimming that article I'm not sure how I feel about that source. The author seems like someone who thinks being a contrarian somehow means you're smarter, i.e. "But if you DO manage to decode my explanations and crude ASCII artwork, I think you'll be in the elite minority who really understands transistors". Same with the way he feels the need to provide his own definitions/explanations of the flow of charge, resistance, etc. Not that what he's saying is wrong, but he seems like he's deliberately going against convention for sake of trying to sound edgy and smart. Finally, I swear that I heard a good explanation of why the emitter current really is 'controlled' by the base current, in a class on semiconductor physics, contrary to what that author is claiming. Unfortunately I can't remember :/ Maybe I'll try and take some time to brush up on it.
    0
  • Allen_7
    so how to know if there is water leakage?
    if the temperature remains in a normal level, can I assume there is no leakage yet?
    0
  • nitrium
    Anonymous said:
    You're implication is that a case should be made noisier to remove GPU heat, and use a quieter GPU cooler to compensate. But if you blow the heat out the back, the extra noise can be taken care of by a case with fewer, more strategically located vents. And the 3C difference meant something to me in the SBM series :D

    Case fans are far, far quieter than GPU blowers! A couple of 140mm fans at 800-1200 rpm makes almost no noise and shifts incredible amounts of air through the case, whereas a blower GPU at 4500 rpm sounds like a jet engine. I'll take an open air GPU cooler and two big case fans any day, despite a nominally higher case temperature - you get a cooler GPU and a far quieter system.
    2
  • Crashman
    Anonymous said:
    Anonymous said:
    Anonymous said:
    Blower GPU have worst quality coolers and provide lower OC capabilities. Not only that, but throttle and offer less stability... and are noisier...

    The only reason to buy one is because you overlooked the importance of a good case, and especially if you are planning on multi-gpu setups.

    I can only disagree with the writer finding open-air cooler defective. Best example in the news, the 1080GTX FE.
    Disagreeing doesn't make you right though. Nvidia put a bunch of effort into its top blower cooler and it worked very well. Dumping that heat into your case isn't simply a bad idea, it's the kind of idea that makes me question your judgement on just about anything. And getting five upvotes from people with equally poor judgement isn't going to change my analysis.
    Wow, self-righteous much?

    Just look at the industry. If blowers were the ideal solution for cooling on air, why isn't everyone using them, especially in the higher-end cards? Maybe you think all the OEMs building graphics cards are idiots and can't learn from their decades of experience?

    They're making them because you're buying them. And you're buying them because people are telling you to. And people are telling you to buy them because they're quieter. But then you need more case ventilation, and that means you lose most of your noise advantage.

    In other words, if you were buying blue cards, they'd be selling blue cards. If you were buying cards with rusty metal covers, they'd sell you cards with rusty metal covers. Engineering has nothing to do with it.

    Anonymous said:
    What if Nvidia only uses blowers as a safe bet - to mitigate against people with poor case circulation - as redgarl mentioned? Or maybe because they're cheaper, having only 1 fan, and Nvidia is content to let their OEMs worry about more elaborate cooling solutions that allow the GPU to stretch is legs?
    Chris Angelini wrote a huge piece about the huge expense Nvidia put into designing its better-performing cooler, something like 4 years ago. The coolers you prefer are easier and cheaper to design, cost less to produce, and OEMs are extra happy to give you a cheaper cooler that's lighter to ship.

    Anonymous said:
    Blowers have one disadvantage I haven't seen mentioned, which is negative pressure. By exhausting out the back, they suck a lot of dust into your case, especially if you have a multi-GPU setup. The way to combat this is with dust filters and positive pressure, but the blowers mean you need high intake CFMs, which will turn your PC into an absolute wind tunnel and clog your dust filters very quickly.
    Wait, you'd better rethink your plan on cooling then. Most cases also have an exhaust fan behind the CPU. You could have two intake fans to match the CPU and GPU, but...hey, if you're looking at better case airflow to cool your box-heater, you're clogging up dust filters anyway.

    Anonymous said:
    I agree with Mopar63's conclusion, which is that open air cooling doesn't raise case temps much, and case temps aren't really a limiting factor for anything. So, while it seems less elegant than to exhaust the waste heat, it is an exercise in optimizing the limiting factor, which is nearly always GPU temps. So, it works out that if you're not going with water cooling, your best bet is open air and decent case airflow.
    Great. My experience shows otherwise. That is, my experience. Not a bunch of talking, a bunch of building. Your experience might be different.


    Anonymous said:
    Normally, I prefer rational argument to downvotes, but your tone has earned you my downvote. As a site staff member, you might think more about how to interact with readers. You are in a privileged position of controlling what's in the article, so if people disagree with you, there's no need to get nasty. All of the other writers I've seen comment in the forums seem to understand this.

    Actually, I'm writing for other people. As in, those who care about how things work rather than how they wished they would work. It's like when the entire High School Auto Shop told me that the 205/50's I wanted for the front of my car were wider than the 275/60's I wanted in back because they had the firmly held belief "50's are wider than 60's": I take your downvote as a compliment, it means I've gotten my point across.
    0
  • Crashman
    Anonymous said:
    3°C on the graphics card can be the difference between archiving the maximum boost speed and a reduced clock if these 3°C fall into the threshold.
    Besides that it's nothing to be concerned about even though some people try to convince others that it might be the difference between life and death.
    I actually cared mostly in the System Builder Marathon because it was the difference between 4.4 GHz and 4.5 GHz in a performance competition. All of my cards had enough cooling, it was the CPU that ran hot when an even bigger CPU cooler would have broken budget.

    But we'll just keep that between us :)
    -1
  • nitrium
    Anonymous said:
    They're making them because you're buying them. And you're buying them because people are telling you to. And people are telling you to buy them because they're quieter. But then you need more case ventilation, and that means you lose most of your noise advantage.

    That's absolute nonsense, and I suspect you know it. Big case fans (140 mm) are effectively silent and shift far more cfms than small loud GPU blowers. Open air GPU coolers are in most cases more effective than blowers IF the case is sufficiently vented with fans - and that can be trivially achieved with practically no additional acoustic overhead.
    2