project: high performance - low power - fanless HTPC build
I would like to share my build of an high performance HTPC for XBMC Eden with a power consumption as low as possible cause it is completely fanless and is also used as a family gaming console in the livving room.

So aim was a balance of enough 3D power and low consumption to be cooled passive. Housing host is the HFX micro from the austrian HFX company. The housing is extreme small - just a bit wider than its ITX-mini mainboard and is able the cool around 80-90W passive.

Here is the bill of parts used:

CPU/APU: AMD A6-3500, 2,1/2,4GHz, tripple core
RAM: DDR3-1666, low voltage, 2 x 2GB
SSD: OCZ Petrol 64GB
POWER: PicoPSU 90W with NB power supply 90W

The AMD A6-3500 APU has a TDP of 65W. Including mainboard the power draw was around 110W out of the box.
Thanks to the APUs quite low frequency is it very well undervoltagable so I ended up with 1,05V (default 1,4V) max core voltage with a PC performing on maximum with only 75W power consumption instead of 110W. Idle is round 21W. So undervoltage is necessarily with passive cooling here.
The gaming performance of the A6-3500 is quite on the same level as Xbox 360/PS3 running even high end games at mid detail level. It has a real DX11 engine and therefore performing better than any intel APU with TDP 65W or less.

But even with undervoltage passive cooling needs at least five heatpipes for getting away the heat when gaming. In XBMC mode max power consumption is around 42W when playing full HD videos leaving enough reserves for what to come in future.

Here are some pictures of my build:

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HFX mini-ITX housing with passive cooling

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the inside with optical drive build in

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four heatpipes onto the APU and one additional for the northbridge

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the northbridge cooler is selfmade - PicoPSU and optical drive bay

Have fun!

nice one !

what temperatures do you have @idle/load/xbmc (1080p watching) ?
I wish to have that HTPC's case's babies
Of course the case temperatures depend on room temperature. With 20°C/68 F ambient temp on idle no warming is feelable. When XBMC runs hard playing 1080p movies the case gets hand warm and on stress testing with all three cores on max plus the OnCore GPU Radeon HD 6530D doing 3D demos the max case temperature is around 50 °C/ 122 F - still touchable. Even with a hot room temperature at 26 °C / 79 F the system keeps stable - tested over hours. So passive cooling is no problem. With bigger housings featuring more cooling surface is should be OK even cooling 100 W TDP CPUs when undervoltaged.

Of course a A6-3500 APU is a bit oversized for a pure XBMC center. But here the PC used as a gaming station, too, doing a real great job (Dirt3 runs at max detail for example). And it guaranties a 100% smooth video playback in XBMC at every resolution. Thanks to DXVA2 the CPU runns with only 8% playing 1080p material.
So the AMD APUs make more sense to me over Intel APUs cause CPU power is well enough for the most tasks, but gaming and video performance is significantly better here with a comparable TDP.

@Ned: If you like one of these housings have a look here: HFX The manufactures web shop accepts international orders. And watch out for the b-stock cases. They are much cheaper.
I love that case and cooling solution!
seems a bit expensive though.
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Pure material cost were not too high with roundabout 500 Euros. In comparison to a standard PC of its class it should be OK. And take into account I save 250 Euro for new gaming console that´s included here plus some energy savings and I am able to repair everything on my own. But it´s some work to build something like that, through. ;-)
Wau, nice one!

May I ask how does one do such custom cooling? Is it possible to buy heatpipes and shape them? and what are the black boxes around the heatpipes in places where they connect to heatsing/processor?
hi urza,

Yes, it is possible to buy them stand alone. In that case u have to make the housing connection with aluminium on your own (like my northbrige connector). But here I bought a complete set including most of the heat pipes and housing/CPU connectors. You can get it in the housing manufacturer web shop (HFX) under the name BorgFX micro

heatpipes can be bend with your fingers very gently. But they are quite fragile, so make it slowly. :-)


Just wondering - does it still work? Hasn't it overheated or does it crash/hang because being undervoltaged?

Your project make me think of trying something very similar... I was considering intel processors for a moment but they are more expensive and their GPU is not as good... so AMD seems like a perfect choice.

Have you considered getting AMD A8 3820 for your project instead of A6 3500? Both of them have TDP 65W so in theory both of them should produce the same amount of heat?

Or am I missing something?

Also, you write that the CPU requires 5 heat pipes for gaming but I can only see only 4 of them on your pictures? Is this correct?

:-) Of course it does and it's used quite often. And no, you did not miss one heat pipe. The APU is cooled with four heatpipes - two on each side. The fifth one is the small one for the northbridge with my selfmade chip connector ( see pics above) making five pipes for the whole system.

I started the project with three pipes on the APU and even this configuration worked OK. But I wanted to have some reserves for warm days so I added the fourth heatpipe. After this very warm German summer I am very sure when saying - it is rocksolid stable!

Undervolting is no problem with a modern CPU. Just find the lowest voltage level an then add one or two step voltage plus to me sure the system will be stable when getting warm. And of course there is no scarification of processing power. It just get more energy efficient and therefore less hot. I did this even with my desktop CPUs to lower its power consumption. 20% or more savings is no problem with the AMD APUs regarding my experience.

Very nice!
Cool man....
Here is an update for my little HTPC - Trinity in ITX format is available now, so I decided to make a stepup to the new A10-5700 APU together with the ASRock Board FM2A75M-ITX.

It turned out to be a little tricky, cause even with the same TDP of 65W both APUs are not comparable with it comes to energy consumption. My old A6-3500 had undervolted a maximum consumption of around 85W all inclusive. The new A10-5700 started with 140W(!) maximum out-of-the-box, which is much too much for a passive cooled housing.

So I started to find out what is eating the most engery here and it turned out to be the new AMD Turbo 3.0 mode of the Trinity APUs. It boosts the CPU part up to 4,0GHz. So a disabled the Turbo compleatly in the ASRock UEFI bioas and additionally reduced the maximum clock slightly to 3,1GHz. This helped to get the System stable at only 1,03V core voltage leading to a maximum consumption of only 89W all inclusive. So this little cut off in CPU performance lead to 50W(!) energy saving and therefore to a passive coolable / noiseless system.

The GPU part was left on normal clock with 760Mhz, so GPU power was not reduced. Moreover it turned out that the GPU part is much more efficient, cause even an overclock to 800Mhz lead to a plus in consumption of only 2W.
So with all this adjustment the A10-5700 is passive coolable with a good housing of course.

But there are some other good side effects coming with this update. The Idle power consumption was obviously greatly improved by AMD, cause it went down from above 30W with Liano to 21W with Trinity. That is comparable to the most efficient Atom Boards!
Moreover power consumtion when viewing Full HD video is less with only 35W - hardly above the old Idle consuption!

So in the end the update was a success giving me a much more performant system - for example Dirt3 is running with maximum graphic detail and oversampling perfectly smooth - without eating more energy, cause what it consumes more playing games is saved in idlemode.

So the A10-5700 is a recommendation for a passive cooled system with a certain performance scarification for the CPU part - not the GPU part!
Thank you.
I´m thinking of getting a A10-5700 myself.

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