Thermal Nightmare

Hardware Build a PC
1

So I got this wild and whacky idea to make a tiny HTPCesque computer with a 7850K APU.

My chosen case was the Minibox M350 and I am guessing that this choice was not a good one because I am having what can only be described as a thermal nightmare. The very kind that keep engineers awake at night.

With bone stock BIOS settings, this monster idles at damn near 60C, even outside of the case. After aggressive underclocking and undervolting, I managed to get this computational thermite reaction to a “mere” 40C.

But when I do anything at all in Windows 8.1, this CPU reignites its hateful flames once more. Downloading updates sends it to 75C. This is all based on Speccy readings which I have fairly good confidence in as idling in Windows is pretty close to BIOS.

My Noctua NH-L9a just simply can’t do the job, even when I crank its fan speeds to 100% at all times.

Just for fun, I tried to play Lost Coast. And at a mere 1024x768, with many texture errors and artifacting this hellish APU hit 101C, so I figured that was enough of that.

What the shit is wrong here?

Before you offend me and point to my paste application or heatsink mounting as faulty, I will assure you it has been done correctly. It has been done correctly, and then redone correctly twice.

The only thing I can really think of at this point is somehow the PicoPSU, being components that inherently heat up, being so near to the APU is a factor. Maybe everything about this build is simply unfeasible.

I’m starting to think that this is just “normal”. I’ve read that 40-50C idling with a stock cooler is pretty usual, and that this Noctua is really no better than stock, just shorter and quieter.

The only other thing I can imagine is a defective unit; displaying temperatures that are not right. The fact that this APU should not even be able to hit 100C supports this.

Any ideas?

2

Don't trust temperature readings from HWMonitor or other temperature monitors as they do not read the temperature information properly. I have had the same problem with my APU and I found that everything except AMD Overdrive misreads the thermal information, give AMD Overdrive a try and see what temps from that

3

So you're saying even the BIOS is wrong? What a twist.

4

Now I don't even know what the hell...

5

I have to go with either bad thermal paste/heat-sink or a bad chip.

Personally, I'd install the most massive heat sink I could find and make sure I CLEANED it before each installation. Sometimes, this requires chiseling the old junk off (though I'd only use a straight razor) since thermal glue may have been used or even really old compound. But usually, iopropyl rubbing alcohol and a thorough wiping of the heat-sink and chip will suffice. Personally, I do this every single time I separate the 2 because if you forget to wipe off the old goo (old thermal compound) you might as well be using a throw pillow or not using anything at all.

I'd even suggest NOT using your fingers since your skin oil can actually decrease the ability of the compound to work as efficiently too. I know some people would like to argue this and even show how peanut butter will work -- which it will -- but it won't work for long. Point being, use quality compound that is formulated for high heat transfer.

And while on the subject of goo (thermal compound), less is better -- you're not making a PBJ! You want the metal surfaces to contact each other with thermal compound filling in the microscopic voids. So a thin film of compound is really all that's necessary.

Finally, you say you have it mounted correctly and have done it multiple times but I'd really like to see this set up before I ruled that out too. Sorry if that's offensive, but you'd be surprised how many people I see who say it's right when it isn't.

 

6

Used 99.9% Isopropyl

Used specialty electronics microfiber cloths

Used the pea method

Have used this same cooler on a previous build with great success

 

And what do you mean by "See this setup?"

7

Alright....so I'm guessing "Thermal Margin" does not mean the same thing that I thought it meant.

I think it might be "Margin until TJMax/Shutdown"

This is what it looks like after 20ish minutes of Prime95

8

what happens if you keep the lid off? Does the fan do anything? Also if you have an hdd above the fan it can't cool a damn thing.