Cooling Quietly

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Revision as of 21:42, 9 December 2014 by Darcy (talk | contribs) (Low power computing)

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Time.png Outdated: most of the information in this page is for hardware 5+ years old

Well, you don't want to drown out your nice sound do you?

There are several different approaches to keeping your system quiet and cool, so we'll look at them all in depth.

Isolate noisy machine(s)

One of the easiest ways to keep your Myth system quiet is to (basically) throw it in the cupboard — don't worry, this isn't as drastic as it sounds. As your probably know, MythTV (like most bits and bobs of Linux) is highly network aware, and will allow you to run a separate backend and frontend. All of the noisy hot stuff, such as TV cards, hard drives, and Terahertz Athlons can be thrown into the backend and kept under the stairs; you can install a low-powered small machine under the TV. All of the control can be done from the frontend, which will just request TV streams from the backend over the network. The downside of this of course is that you need to be able to afford two separate machines, although it will make expandability much easier further down the road.

Viewing high-definition recordings requires much more processing power; decoding a 1920x1080 MPEG2 is much more intensive than viewing a 400x480 SD video of any format. It is thus more difficult to quiet a high-def frontend when you likely need a CPU over 2 GHz and/or a hardware video accelerator (IDCT via XvMC).

There is however an alternative for the cupboard approach. Several CAT5 KVM extenders exist on the market. Such a device extends your VGA, mouse, and keyboard cables using CAT5 network cable. You can extend up to 30 meters. One setup in use includes two Aten CE220 KVM extenders to extend my Dual Head development box from the hallway closet into the living room. This setup now has only two LCD screens, a mouse, and a keyboard sitting in the living room generating zero noise. It also includes an SPDIF cable running from the living room amplifier and a cinch TV-out cable to the TV-set.

Software solutions

TLP can be used to set automatic power saving modes on modern Intel and AMD processors and is typically in the distro repositories.

System components

Even if you can't avoid having your quad 30GHz Xeon Myth array sitting under the TV, there are still many ways you can reduce the amount of noise today's computers like to kick out. There are many specialist computing companies out there specializing in quiet hardware for use in HTPC environments, and I'll list a few of the products you might want to splash out on:

Quieting fans

PWM fans are the best option for cooling as the motherboard can control the speed based on the case temperature. These have 4-pin connectors that will appear similar to the header for the CPU fan and may come with rubber mounting dampers which are highly recommended. Ensure the motherboard supports a 4 pin chassis fan before purchasing. The BIOS usually has options to select 'silent' operation where the chassis fan(s) may not spin up until needed.

Another option is to add variable resistors to the fan circuit, altering the voltage supplied to your fans. Normal fans runs at 12V, but by lowering the voltage to 7V you will get lower RPM's and thus quieter fans at the cost of air throughput.

CPU coolers in modern processors (c2014) are typically quiet and no special attention is required.

Quiet and/or adaptive power supplies units (PSU) can also help reduce noise by a considerable degree. There are some premium PSUs that just use a heatsink for cooling, and thus run totally silent. However, they don't do much for the cooling of your case! A better solution are high efficiency PSUs (80 Plus Gold) or a pico-PSU and choose a PSU with a rating closest to your computer usage. It is highly recommended that a power meter is used to ensure that you will not exceed the supply rating of the PSU.

CPU choice

Use a cooler processor! Several years back, CPUs kicked out a helluva lot of heat and caused systems to become uncomfortably hot. More recently, AMD and Intel have realized the error of their ways and modern processors are faster than ever, but without generating enough heat to melt your case. Assuming you're using a hardware capture device (either a DVB card or one of the TV cards supported by ivtv) and a reasonably good graphics card. One of the good things about Myth is that 90% of the common functions don't require a powerful CPU at all, so you can often pick and choose the CPU that runs at the lowest power and heat output.

See the section on frontend hardware to choose an appropriate CPU to meet your requirements.

Low power computing

Low power computing is running your processor at less than its full clock speed and voltage to produce less heat and use less energy. The heat produced by a particular processor increases linearly with increases in clock speed and quadratically with an increase in voltage (the change in heat production is the square of the change in voltage.) There are two ways to reduce your processor's voltage and clock speed. You can either have it done automatically if your processor supports such a function and you can do it manually.

Automatic CPU frequency and voltage scaling

Intel Processors

Modern Haswell era Intel processors are handled by the kernel p-state driver and have multiple sleep states (C1 to C10) enabling low power and low heat CPUs. This is typically handled automatically but the BIOS settings should be checked to ensure the BIOS is able to put the processor into these C-states. Use <texttt>powertop</texttt> to check if these low power states are being reached.

If maximum power usage is a problem, the highest frequency of the processor can be capped in the BIOS resulting in a drop in maximum power draw. The processor will otherwise reduce frequency and voltage automatically. Otherwise, T versions of the Intel range are low power variants but may exhibit the same power draw at idle.

AMD Processors

If you have an AMD please add information in here


Vibration from wobbly components can often cause irritating buzzing noises. Regularly give your fans a clean by blasting them with compressed air (be careful as you can overspeed smaller fans), and if vibration seems to be a problem you can dampen your fans by placing rubber or silicone washers between the fan and the mounting. Other moving components (such as hard drives and optical drives) should be secured mechanically well. You could consider mounting your drives in a dampening cage or using anti-vibration grommets. Antec uses the latter to great effect. I'm personally a big fan of the Cooler Master 620's spring-clip mechanism of mounting optical drives; these are screwed in on one side, and are forced into a good fit by a spring clip on the other side.

Related to vibration are stupidly fast optical drives running at 16x or 52x or something similarly daft. To watch DVDs and play CDs, you shouldn't need a drive faster than 1x DVD or 1xCD respectively. The DVD and CD specifications are written such that a DVD should playback video or video perfectly well at the drive's lowest available speed, YMMV.

As of this edit there are no optical drives on the market that are specifically advertised as being quiet or having quietness as a feature. Some drives have "quiet" firmware/utilities available which will limit the speed to a more reasonable and less deafening level. Since almost all drives require that their firmware be upgraded using Windows or DOS you may run into difficulty attempting this method with a Linux based computer running MythTV. You do have the option of putting a drive into a Windows based computer, applying the firmware alteration, and then putting it back in your Linux based computer (a variation on this theme is to always have a FreeDOS bootable partition). If you have the choice between an 8x DVD drive and a 16x DVD drive, choose the slower (8x) one. The only place MythTV needs fast disc access is when ripping a CD or DVD. You may also want to experiment with hdparm, setcd or speedcontrol; All claim to be able to reduce the maximum speed of optical drives. setcd may require a patch to work with newer drives, see debian bug 367008. SPCR has a forum thread on the subject. But there appears to be no definitive study of the comparative quietness of DVD/CD drives.

Chassis quieting

Keeping all those cables tidy can do wonders for airflow within your case, and do away with the need for more stupidly fast fans. You can tie bundles of power cables together using zip ties, braiding or spiral wrap (my personal favourite, since it's easy to apply and remove). Don't forget The Art of Cable Folding for those with tight wallets.

Last but not least, you can also attempt to soundproof your case with acoustic material. This is essentially sticky-backed foam that does a lot to absorb noise from inside the case, although you'll need a case with enough free space inside to accommodate its thickness. I've never tried this myself, but a lot of people swear by it. Lian Li and Zalman make some very pretty (and pretty expensive) cases fitted with this sort of anti-noise technology as standard, so those of you who want a big, quiet case might want to consider splashing out on those.

And, even more finally (:-), you can uncouple the case mechanically from whatever is underneath it, or whatever it's underneath. Conducted noise which is then radiated by something else is a major component of the noise which a PC can put out — which explains the rubber mounts you can get for hard drives. They're good for noise, but bad for thermal conduction. (You do have a fan blowing directly on your hard drives, right?) Standing the chassis on a piece of carpet, or even better, underlay will cut down on transmitted noise through the floorboards, plasterboard etc.

That'll about do it for now, hope you enjoyed the update ;)

For lots of information on keeping your HTPC (and PCs in general) quiet the website Silent PC Review has some excellent guides, reviews and forums to provide you with all the details you need. Their recommended hardware section contains lots of hard numbers.

Useful Links

SilentPC Review - Contains reviews and guides on quiet PC cases, fans and components.

See also