Quiet Computing Pt.1 - Airflow and cooling

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  1. Graeme*Kustom*

    Graeme*Kustom* Administrator

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    By Thomas Hawthorn

    Part 1. Airflow and air cooling.

    Quiet PC Guide Part 1. Airflow and air cooling.

    At Kustom PCs we are regularly asked to build quiet systems, or for help in selecting parts to make one.

    Computer components change so fast these days, so for that reason I thought I would make a more general article describing the various factors to take into account when choosing components for a quiet PC.

    The main factor in quiet computing is going to be heat. You can have a very quiet computer with nearly no fans that will only run for a few minutes before overheating, which is of no use.

    Quiet fact:

    Generally, quiet systems will run slightly warmer than a well cooled but noisy computer.

    Building a quiet system.

    Changing the fans in your computer is an easy way to reduce the overall noise in your system. In this first part of the guide we will cover the main areas that need air cooling, and how to accomplish this quietly.

    Most computers have the following fans:

    1. CPU Heatsink and fan. You need a heatsink to cool your CPU, and a fan on that in order to take the heat away.

    2. Graphics card fan. GPUs can get much hotter than a CPU, and yet most manufacturers ship them with small, loud, fast fans. However to ATI and Nvidia’s credit recently, their fans are now temperature controlled. (We’ll talk later about graphics cards, what to do with them, or what to select if making a new computer).

    3. PSU fan. The Power Supply Unit has to step down 230v to 12v and below. Because of the transformers it also generates heat, and has heatsinks and fans to disperse this heat.

    4. Case fans. The size and position of these depends entirely on your case, but generally there will be at least one at the front bringing in cool air, and/or one at the back exhausting air.
     
  2. Graeme*Kustom*

    Graeme*Kustom* Administrator

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    CPU Heatsink / fan selection.

    Kustom PCs has a great selection of coolers for various CPUs here http://www.kustompcs.co.uk/acatalog/Kustom_PCs_Shop_CPU_Quiet_Coolers_16.html. When selecting a CPU heatsink, make sure it’s compatible with your motherboard/processor. The CPU that they are intended for can be found within the description.

    The material that a heatsink is made from can greatly influence the cooling properties of it. For example, copper conducts heat better than aluminium, therefore a cooler which is made of copper will be able to remove heat from a processor much faster.

    The other thing to look at is the size of the fan being used. In general, the larger the fan, the less it has to spin to generate the same airflow as a smaller fan spinning faster. Basically a larger fan makes less noise.

    If we were to take the Zalman 7700CU for example, this is the successor to the Zalman 7000 CU, which was a 92mm fan, the 7700CU has a larger 120mm fan, therefore it can spin slower, generate less noise but still blow enough air over the copper fins to keep the CPU cool under load. Most modern motherboards from ASUS now also support Quiet Fan, which is a BIOS level monitor that adjusts the rpm of the fan according to how hot the CPU is. This means that you could for example have a silent computer for desktop use, then when you start a game and the computer gets hotter, the fan will spin up to keep the CPU cool. It is important to point out that even at full speed the 120mm fan would still be reasonably quiet.

    A lot of people think that using a fan in a computer means noise, when in fact, if you use one or two well placed case fans, you can reduce the noise. This is because the overall temperature is lower.
     
  3. Graeme*Kustom*

    Graeme*Kustom* Administrator

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    Graphics Card

    If you’re looking to buy a new graphics card when making a quiet system, first think about what you need it to do. If you intend to do gaming, then you may be looking at a high performance card with an after-market cooler such as the arctic cooler range. If however you don’t need fast gaming performance, then look for a card manufactured with a passive cooler.

    High performance graphics and low noise never used to go hand in hand, but now there are a range of after-market coolers available which can make this possible. Again thinking about heat, a passive cooler isn’t always the answer. While on the surface it may appear that this would be the most quiet option, for high performance cards you would need to have other airflow in the case to remove the heat that would build up. However something like the Arctic cooler range have two distinct advantages:
    1. They are designed to still move air, but quietly.
    2. They vent air straight out the back of the case as opposed to blowing air in against the natural flow.

    Major manufacturers have recognised the quiet trend in recent years, and have attempted to make their cards more acceptable to this market. As such you will now find most graphics card fans are temperature sensitive, or the drivers have functions built in which recognise when the computer is playing a game, and when it’s on the desktop. You can however take this further. There are now tools such as the ATI Tool from (wherever) which can let you alter the speed of the fan. This is particularly useful, because it allows you to change the clock speed of your card and set a different 3d profile and desktop profile.

    Bearing in mind what has been said before about heat, using the ATI Tool and a compatible graphics card, you would have a 3d profile which runs the card at normal speed, and a desktop profile which actually clocks the card down below normal. This means - less overall heat being generated. You can also argue that you are doing your part for reducing power consumption in the home.

    If you do not need great gaming performance, try seeking out a graphics card that is built with a passive cooler from the factory. When a graphics chip is not needed to perform 3d, they run a lot cooler. Unlike the situation with the high performance cards, these do not generate a lot of heat, therefore as long as you have some airflow in the case, this will be enough.
     
  4. Graeme*Kustom*

    Graeme*Kustom* Administrator

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    Power Supply

    Selecting the right power supply is very important. While it is possible to retro fit an existing PSU with a new quieter fan, I would strongly recommend against this. Remember that all power supplies have gone through various stages of quality control and testing, this includes finding the right amount of airflow for the unit. If you have bought a low cost PSU, changing loud fans for quiet ones could result in overheating and the PSU could burn out because they have saved money by not adding in large heatsinks.

    Instead, if your current power supply is too loud, I would recommend replacing it with a quiet model.

    The Silenx Range of power supplies available from Kustom PCs Power supplies section are made for being quiet but powerful. One thing to consider when buying one of these is that unlike most other power supplies which are designed to help ventilate a case, Silenx PSUs are only moving enough air to keep themselves cool. You may want to consider a case fan near the rear of your case. This is covered later.

    If you have a power supply with a 120mm fan on the bottom, such as a Nexus, then you have a very good situation because it’s positioned perfectly to take air away from around the CPU, meaning hot air is vented straight out of the case instead of being recycled and ultimately raising the temperature.

    I will give a brief mention to Fanless power supplies. In my experience, these PSUs raise case temperature, and usually as they are sitting next to your processor, this also rises. While you save on a fan, you usually have to supplement this with airflow from another case fan, and the point is lost.
     
  5. Graeme*Kustom*

    Graeme*Kustom* Administrator

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    Case Fans

    Quiet fact.
    A larger fan has a better noise to air movement ratio.

    The last piece of the airflow puzzle is case fans. The correct selection and positioning of these can be the deciding factor in overall noise.

    The ideal situation for cooling your components is as below.

    (Pic of case with airflow arrows and indications of what these are.)

    The main points here are:
    1. A source of cool air into the case
    2. At least one exhaust fan (which can be the PSU), or two very quiet ones.
    3. Where is the main source of heat coming from, and is the air flow passing the area?


    Point 1. A source of cool air. While it is possible to have cool air drafted into the case by simply having fans exhausting elsewhere, it’s much better to try and have an active but quiet fan bringing air into the case. This provides the components with a steady flow of new air to cool them, rather than recycling the existing air in the case.

    Intake fans should not be placed at the back of the case, given that this is typically where heat is exhausted from the power supply fans. This will only bring hot air back into the case. Instead, aim to have a quiet fan at the front bringing air in.

    Point 2. Exhaust fan. As mentioned in the power supplies section, if you’re using a quiet 80mm based PSU, it may be wise to put in an exhaust fan near (usually just underneath) the power supply. This is also especially useful when using a power supply that is temperature sensitive. Removing hot air before it goes through the power supply will mean less noise from it, hence the overall effect we’re trying to get.

    Point 3. Main source of heat. This can vary from computer to computer, but generally you want to make sure that air is passing by the graphics card and CPU. It’s also worth giving a mention to motherboard chipsets. As these have progressed they have become quite powerful and as a result can get quite hot. Currently most of the ASUS motherboards use passive heat sinks, but it’s worth making sure that there is some air getting to it.
     
  6. Graeme*Kustom*

    Graeme*Kustom* Administrator

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    Cable Management...

    This subject is a guide and article in itself. I’ll write this later on, but to give this a quick look.

    Kustom PCs sells rounded IDE cables and other Cable management equipment from cable ties to spiral wrap. All of these used in conjunction can lower temperature and help in making your computer quiet. Flat cables tend to obstruct air flow, and so can make components get hotter, and that means more fans, or louder ones are needed to make up the deficit.

    At the minimum, you should be looking to cable tie your power cables out of the way of fans and air ways, and use rounded cables. If you want to go further than this, try looking in your case for spaces where cables could be tied and tucked away, look at spiral wrapping to help hold cables together. If you’re still stuck for places to put them out of the way, you can add cable tidy clips to your case that will stick onto a flat surface and hold them out of the way.