Building a fanless PC is now realistic. But it still ain't cheap

Here's a few pointers if you wanted to get cracking

When it comes to PC performance the elephant in the room is heat generation.

Generally, the cooler a CPU or GPU can be kept the faster it will run, hence mega-overclocked systems running liquid nitrogen cooling systems and producing mind-numbingly high benchmark scores and more clouds than your average Pink Floyd concert.

For the rest of us mere mortals keeping things cool generally means having an active cooling system, either with fans on all the major components or, if going down the water cooled route, fans in the radiator(s). No matter how slowly they spin, they still produce noise to some degree.

By carefully balancing quiet CPU and case fans with a good fan controller it’s possible to get a system that is barely audible – indeed, almost silent. That is, of course, a subjective experience: one person’s barely audible might be another’s annoying hum. But what if you want a totally silent, fanless, full-sized PC rather than a small format one (based around an ITX motherboard)? That – frankly – is a lot easier path to go down.

You'll be happy to know you can buy an off-the-shelf silent system from specialists like Quiet PC or have a crack at building your own, all without resorting to extreme passive cooling solutions.

Fan free future?

It wasn’t long ago that if you wanted to build your own totally fanless PC you had to give up all hope of having a high performance rig just because of worrying about getting rid of the heat build-up from power-hungry CPUs. Today’s CPU designs are much more power efficient than their predecessors meaning that it is possible to build better performing passive setups.

Now, I must admit to thinking along the same lines of old, that a low-speed Intel i3 or – at the most – an i5 or an AMD equivalent was about the limit. Yet, after chatting to Paul Lee, the technical maestro at Quiet PC, it seems I was way too conservative as Quiet PC builds passive PCs using Intel’s mighty i7-6700K CPU, although choosing a processor lower down in the food chain may bring more peace of mind.

But even then, a K-series i7 is not the limit as a search around the web showed there are some very powerful Xeon workstations that don’t have a fan in sight and they are using CPUs with TDP’s of well over 100W using exotic bespoke passive cooling solutions.

But surely a CPU with a TDP of 91Watts (in the case of the i7-6700K) is going to need one hell of a passive cooler. Well, yes because without a fan these coolers need a lot of heatpipes and a large area of cooling fins to dissipate the heat. Quiet PC uses the Nofan CR-95C to keep its i7-6700K Skylake Silent system cool and it’s no shrinking violet; it’s a huge circular cooler measuring 180mm in diameter and 148mm high that, in itself brings, some compromises.

It will obscure the first PCI-E x16 slot on a great many motherboards and the same applies to memory module selection. Even then, its TDP of 95W is awfully close to the TDP of the processor which means any serious overclocking is out.

More conventionally designed coolers are the HR-22 and Macho Zero tower coolers from Thermalright which are still big but do have the added advantage of being able to support cooling fans if needed. Passively cooled graphics cards have always been rare beasts in comparison to their actively cooled brethren and if the integrated graphics of the CPU can deliver the performance you require, then not having a dedicated graphics card will help reduce the thermal footprint inside the case. Because of the heat a GPU generates, the passive versions have always been based around lower-powered GPUs – for example Palit’s Geforce GTX750 Ti Kalmx is the currently the fastest passively cooled card to buy off the shelf.

There are third party passive GPU coolers around (such as Arctic Cooling’s Accelero S1 Plus) that support a number of differing GPUs – but, just as with the CPU, without any airflow in the case, the TDP of the GPU is very important to bear in mind when fitting your own cooler.

Even rarer than passive graphics cards are passive power supplies and the ones that are available are generally restricted to the 400W – 520W range. Higher wattage supplies produce more heat regardless of how efficient they are but you may be able to get away with using less power than you think. An online power calculator such as the eXtreme Power Suppy Calculator (http://outervision.com/power-supply-calculator) will give a ballpark figure of how much the system will use.

For quick, silent and relatively cool running storage, a SDD in either 2.5in or M.2 format is the way to go.

If you are thinking about building a small format, relatively low-powered passive rig using an iTX or mATX rather than a full-sized ATX motherboard then there are all manner of passive smaller HTPC cases on the market, from the reasonably priced to the frankly ridiculous.

Some, like Streacom’s FC9WS and FC10WS Alpha, even use built-in heatpipe CPU cooling technology that employs the case as a part of the thermal design. For a full sized ATX motherboard there are a number of fanless PC cases around. Nofan’s CS-80, for example, has plenty of mesh panels built into its design to allow for natural convention. Quiet PC use this case for their silent builds as well as the Nofan CS-30 (Quiet PC remove the two case fans that come with the case). Then there is the SilverStone FT03, a tower case which doesn’t really look like a PC case. It uses 2.5mm thick aluminium in its construction to help dissipate heat and uses natural vertical convection cooling as part of its design.

So a fanless PC with good performance is possible to build but – and this is a very big but – you need to think about what you need the system to do and match the components very carefully to do the job, paying particular attention to the CPUs' and GPUs' TDP.

Also, where you put the system is another thing to think very carefully about; ideally, it needs to be placed where at least some air can circulate around it. Without any active case cooling all the component’s inside are going to need all the help they can get.

The other thing to take into account is cost; going totally silent can be an expensive option. ®

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