Cooling Cooling a Ryzen 5900X and Crappy Motherboard (Was: Cooling a Ryzen 9 9950X... on air?)

D'you know, I think the problem might be the motherboard VRMs. They're bare, no heatsink - and I'm not using a CPU cooler with a downward-firing fan anymore, so they're not getting direct airflow.

I did a quick test: running 24 Tesseract workers causes several panic-drops to 547MHz. Turning up the case fans a little... it's stuck at a 4.1GHz boost, but does not drop to 547MHz.

Hmm.

 

Boo, tier F - that says I shouldn't even be trying anything above a 65W chip. (Which doesn't seem right, the 2700X was 105W TDP just like the 5900X!)

There's room for a 120mm or 140mm fan in the side panel, wonder if that'd help any?

Huh, hadn't thought of that - I've always had top fans as outtakes. Wonder if I can get at it without removing the heatsink?

 

I'm thinking: reverse the top fan as an intake, maybe add a side-panel fan, and maybe add a floor intake fan too - there's room for one. I'm going to do some measuring, too, (or as best I can without removing the HSF) and figure out what size heatsinks I'd need to stick on the top.

Given that just turning the existing intake fans up a bit stopped it from plummeting down to 547MHz, that should definitely solve the problem!

Oh, and this morning? Woke from suspend with no USB problems at all, I've changed nothing. <shrug>

EDIT:
Scratch the side-panel intake idea: there's no room now I've got a massive HSF in there.

EDIT EDIT:
Flipped the roof fan: the CPU temperature has dropped, and is now at 64°C roughly halfway through the Tesseract run, which is nice. It has not, however, made it sustain anything above 4.1GHz. In fact, now it's dropping to 4GHz? Even though the CPU's a good four, five degrees cooler? Whuh?

EDIT EDIT:
Adjusted the fan curves to start ramping earlier (though they're still quiet) - which affects the two CPU fans and the one Noctua PWM case fan at the rear, the other three are on a manual reheostat. The result? CPU's nice and cool... but also sitting at 4.2-4.1GHz even on an ImageMagick run, when it used to hit 4.4GHz before I started fiddling.

No, none of this makes any sense.

EDIT EDIT EDIT:
Sometimes, you have to think outside the box...


Literally. Random 120mm USB-powered fan I had from a previous project, which was lying around doing nothing. If there's no room inside the case, it can hang off the outside! Turned the front intake fans up on the rheostat and the now-intake top fan down with its H-L switch, 'cos it was the noisiest of the three intakes. Well, four, now.

CPU is now idling at 27°C, at an 18.1°C ambient. Peaks at 62°C, sits during the Tesseract 24-worker run at 59°C. Still insisting that it can't go over 4.1GHz for that, though, but it's happy at 4.4GHz during the ImageMagic and jpegcrush steps.

This does mean I'll have to blow the dust out a lot more frequently, mind...

EDIT EDIT EDIT EDIT:
Found Eco Mode, gave that a go. Drops about 30W 65W from the wall at full load, but you lose around 1GHz all-core boost. From 3m8s to generate the PDFs to 3m43s. Not a massive difference, but not worth a 30W 65W saving.

 

Tried -10 on the curve optimiser again, even though that shouldn't be cooling related 'cos reducing the voltage would make things run cooler... didn't even boot.

Trying -5 now, just as a nod to doing something.

EDIT:
Temperatures actually spike higher, and the overall performance seems unchanged. Now, I was only joking about Asus having labelled the positive/negative sign option backwards, but...

 

I was really, really hoping that it was the nice big chunky ceramic chuffers that were the problem, 'cos I could buy a pack of 10x10xSomething heatsinks and stick 'em on the top, nice and easy.

It is not.



Not the best thermal image I've ever taken, but you get the idea: the ceramic bois are relatively cool, but the little flat surface-mount chaps to their left? Spicy.

Not really sure what I can do about that.

(No, the big heatsink isn't clap-cold - it's just got a very low thermal emissivity 'cos it's shiny metal!)

EDIT:
It's these.



EDIT EDIT:
Quick-and-nasty overlay:



So yeah, sinking the big ceramics won't help.

EDIT EDIT EDIT:
Less nasty though still nasty overlay:

 

That'll be using a strip of squidgy thermal stuff (got that!) and is screwed down onto the board (can't do that... unless I drill some holes through the motherboard, and then I guess my overheating problems will be solved once and for all!)

 

They're tiny. Like, the bigger square components next to 'em are 10x10mm or thereabouts. They're also thinner than the resistors next to 'em, so without a squidgy pad (which wouldn't hold them in place without mechanical clamping) each heatsink would have to be the same size as the underlying component. In other words, tiny.

There are no screw points anywhere near - closest one is on the wrong side of the EPS connector. I could clamp it to the back of the heatsink, though.

I have neither the time nor the talent, sadly.

 

So no, different Z-height. I'd be cooling the resistors and leaving the MOSFETs to cook.

The gap between the capacitors and the ceramics is way, way thinner than an M.2. Slightly over half the width, maybe?

Like I say: there's no way to get a heatsink onto the MOSFETs without using squidgy pad (which would require mechanical clamping) or putting one tiny one on each (and I don't really want to fiddle with 3x3mm heatsinks, even if you could buy such a thing, and I really don't want to find out if thermal tape will hold them in place with such a tiny surface area and 100-degree temperatures...)