What's under the N2+ heatsink?

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mctom
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What's under the N2+ heatsink?

Post by mctom »

Hi!
So N2+ has no ability to overheat whatsoever and I regret buying a fan for it. ;) It sometimes spins up after I set threshold to 40 degrees.
However, the CPU has a tendency to change its temperature rapidly with a load change. A temperature rise or drop of 15 degrees in 1 second is fairly common.
This obviously does not correspond to heatsink temperature change at all. Heatsink maintains about 33 degrees all the time in my scenario (a mean CPU temperature).

Which leads to a simple conclusion that the heat resistance between CPU and heatsink is pretty high.

So, my question is: What's in there? A thermal pad? A thermal paste? Maybe nothing? ;)

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Re: What's under the N2+ heatsink?

Post by odroid »

We've pasted this thermal grease between CPU and heatsink over several years for all the ODROID boards. It is made in Germany and looks quite reliable.
https://cht-silicones.com/products/greases/SG500


BTW, you might need the fan when your room temperature is 30°C or higher while you run a heavy CPU and GPU intensive load at 2.4Ghz over-clocking more than 30 minutes continuously.
You will meet thermal throttling events frequently without a fan as the follow picture. Therefore I hope you don't regret buying the fan for the next summer. :D
Image

Image
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mctom (Mon Nov 16, 2020 5:40 pm)

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Re: What's under the N2+ heatsink?

Post by mctom »

odroid wrote:
Mon Nov 16, 2020 5:28 pm
you might need the fan when your room temperature is 30°C or higher
Surely won't happen in my house. I live in Poland. I actually quit my last job because I had a desk in a room without a window, and 3kW+ of equipment under test. There was 30°C in there, enough for me to switch a job. ;)

Anyway, I can't complain about the grease then, looks like a decent product indeed. There's nothing to fix here, to be honest, the system never gets too hot or anything, and it can't be overclocked any further. Just being curious. :)

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Re: What's under the N2+ heatsink?

Post by kouklo »

mctom wrote:
Mon Nov 16, 2020 5:07 pm
Hi!
So N2+ has no ability to overheat whatsoever and I regret buying a fan for it. ;) It sometimes spins up after I set threshold to 40 degrees.
However, the CPU has a tendency to change its temperature rapidly with a load change. A temperature rise or drop of 15 degrees in 1 second is fairly common.
This obviously does not correspond to heatsink temperature change at all. Heatsink maintains about 33 degrees all the time in my scenario (a mean CPU temperature).

Which leads to a simple conclusion that the heat resistance between CPU and heatsink is pretty high.

So, my question is: What's in there? A thermal pad? A thermal paste? Maybe nothing? ;)
I like where your head is at buddy, great question!!! I don't know why but for some reason my dumbass just assumed that it was a pad and not paste.
@odroid I'm sure you guys are using a pretty good paste but can it stack up to the enthused market? Stuff like Thermal Grizzly, Arctic Silver, Noctua NT-H1, etc.?
So I have two questions. First, have you guys done anything to prevent me from removing the heatsink and try it myself? Second, does anyone know of a good hardcore Android stress test that just keeps going until I stop it or it crashes? Ya I know I can use one of the million benchmarks out there but they only last for 5ish minutes and I have to restart it again.

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Re: What's under the N2+ heatsink?

Post by odroid »

1. You can remove the heatsink once unscrew the 4 screws on the PCB.
2. We've run stress-ng and glmark2-es2 apps together(in parallel) on Ubuntu to fully utilize the CPU and GPU resources.
We used "StabilityTest" app on Android a few years ago for the same purpose.

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Re: What's under the N2+ heatsink?

Post by mctom »

kouklo wrote:
Tue Nov 17, 2020 9:07 am
I like where your head is at buddy, great question!!!
That's a curse of being an EE professional. ;)

However I trust my colleagues from HK that they did an amazing job as well. If it works, I'm not fixing it.

Anyway, I already screwed my Odroid to the bottom of my desk, to keep my spice nice and silent and tidy, and that's another reason to leave it alone for now. ;)

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Re: What's under the N2+ heatsink?

Post by powerful owl »

mctom wrote:
Mon Nov 16, 2020 5:07 pm
Which leads to a simple conclusion that the heat resistance between CPU and heatsink is pretty high.
According to the datasheet, the junction to case thermal resistance is 3.35 deg C/W, so that's the absolute minimum that could possibly be achieved.

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Re: What's under the N2+ heatsink?

Post by mctom »

Which still is a part of CPU(core) to heatsink resistance, right? ;)

But then again, too lazy to dive into SOC's datasheet, but (pessimistically) assuming its major role in power consumption, let's say that it dissipates 2W at idle and 6W active. In the latter case, we get a temperature difference between CPU and heatsink of about 20 degrees C.
And that seems to be the case, as my room temperature is about 20, heatsink has about 30, and I maxed out CPU temperature at 52 so far, with fan on.

So, yep, another reason to leave that thermal grease alone. ;) Thanks for pointing that out!

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