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MITX APU build idles hot, high power

Last response: in Systems
November 17, 2012 2:32:32 AM

I decided to piece together an APU box in a mITX form-factor to use as a HTPC.

Here's the thing- the system is drawing way to much power. The CPU is @ 60C when I sit idle in the bios. But, wait, it isn't a heatsink mounting problem, I'm pretty sure-

1) Heatsink is almost too hot to touch

2) My Kill-a-watt says the box is drawing 110 watts on boot, 50 watts at idle on the Windows desktop!!! For heavens sake, my Athlon II X3 w/ HD5670 idled at 80W.

The only things in this machine are:

1) 65W APU

2) Samsung SSD

3) Asrock FM2 mITX motherboard

4) Scythe Kozuti fan

That's it! The fan can't draw that much, and neither can the SSD. The APU seems fully functional- I installed Windows, and I'm running applications no problem. I'm thinking it's unlikely there is a short in my case wiring, because I'd smell something, it would burn more than a few amps, and the CPU wouldn't be getting so hot.

So, can the motherboard be responsible? I've been reading that this particular motherboard is not 100% reliable, but I didn't want to wait for Zotac to come out with theirs...
November 17, 2012 3:35:25 AM

wow my 3670K htpc only pulls 120 watt @ full load, What past did you use ?
November 17, 2012 4:05:57 AM

It's the A10-5700, which should in theory basically never draw as much as a 100W APU like yours.
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November 17, 2012 6:25:34 PM

I'd like to reiterate tourists question of "Which paste did you use?"

Could well be a bad application of thermal paste, too much can just be as bad as not enough!!
November 19, 2012 6:25:05 AM

bluerotkev said:
I'd like to reiterate tourists question of "Which paste did you use?"

Could well be a bad application of thermal paste, too much can just be as bad as not enough!!

Ah, he meant "paste"! I used Arctic Silver 5. It actually turns out I didn't have good contact in the middle- I put it on very thinly, and for some reason the left and right edges were making contact but not the middle (this disturbs me a little- is my cooler warped? Did I put it on too tight?). I added more, tiny bit by tiny bit, until I had 100% coverage. This improved my idle BIOS temps somewhat- 50C instead of 60C. Still drawing a ton of power though.

Edit: Well, ok, it doesn't stay at 50C. It is slowly climbing; @ 56C now. Does the CPU run full-bore in the BIOS or something? I am not used to this kind of behavior at all.

Edit2: I'm reading that is normal...? (Perhaps the issue here is a combo of me being sensitive to heat/power because of the build, and the generally lower performance low-profile cooler- in other words, my other computers also climb in temps in the BIOS, just much much more slowly)
November 19, 2012 7:19:12 AM

Ok, I've discovered that apparently if I use UEFI boot, it boots reliably, probably because it spends so little time in the BIOS thus not overtaxing the PSU. It seems to run cool at Windows desktop, which is good enough I suppose.

I'm still not thrilled about the amount of power the motherboard seems to be using though. Can anyone comment on what a mini-ITX board *should* draw?