Comment by geerlingguy | Hacker News Reader

Comment by geerlingguy | Hacker News Reader

Awesome work, and I'm glad you could post some results! I'm hoping to get time to delid one, put on a peltier cooler, and try to control the temperature a little better for a run to see how high it'll go before either burning up or going unstable.

From my testing on clocks on the Pi 5, it looks like the default clock of 2.4 GHz is pretty close to the sweet spot for this chip (BCM2712), and you burn a lot of power for small incremental gains after that[1]. (Which you seem to also show with the 3.3 GHz overclock!).

I also spoke to one of the Pi engineers about the chip behavior at higher clocks, and he suggested unlike some chips, this chip might run more stably at higher temperatures (like 50-60°C) rather than 'as cold as you can get it'. So that poses some challenges since most cooling solutions aren't tuned for 'keep a temperature' but instead 'get it as cold as possible', without a lot of manual tweaking.

[1] https://www.jeffgeerling.com/blog/2023/overclocking-and-unde...

Did the engineer explain why the higher temps contribute to stability? I've not heard of such a phenomenon before.

No physics-level explanation, just that they found the chips to be more stable in testing when they were a little warmer vs a little colder. The key was to keep them around that temperature, though, which still requires a good amount of cooling the more voltage that runs through it!

Just... he mentioned I might not have as much success using LN2 or something more exotic, compared to standard water or Peltier cooling.

That's pretty crazy, thanks for sharing, Jeff.

Overclocking was my bread and butter as a [relatively] broke teenager in the late nineties, around the era of the first Athlon Thunderbirds, when you could take a 1GHz chip and [maybe] OC it to 1.5Ghz. It was a great time to be alive, and yet this is the first case I've heard of where LN2 would not give you a dramatically better result 99.99%+ of the time! I still miss HardOCP and Kyle Bennett and his team's reviews.

That one t-bird with char spots... It still worked reliably somehow, I might even have it in a box somewhere. Those swirly finned CPU coolers were shit! I came home every day after school and volted/burned the hell out of that poor chip, not realizing what I was doing.. lol.

I still remember my dual celeron 450 clocked to 900 mhz. Those chips ran rock solid at double their rated clock, no didling the voltage or anything. Just needed decent cooling. Never mind that at the time having 2 processors was nearly useless.

Heh, back in those days decent cooling was a lot easier than now (for overclocking, at least).

That's one nice thing working on these little mobile chips—I don't need a $300 cooler, I can use a cheap little water block, or a small peltier element that doesn't cost much at all... and it's not being a space heater for the room. It's only pulling maybe 10-20W max.

Where are these "cheap" water blocks you speak of? Haha, I've never encountered such a thing.

Except maybe the $100 Corsair liquid coolers, but c'mon, they aren't real water cooling

I still remember that time, when you actually waited for the low end chip to be released and get it as fast as the earlier released flagships. Was a different time. But I also roughly remember having a dual socket board at the time with two overclocked celerons if my mind does not fool me. Funnily my wife is still using this 25 year old PC case, in which I glued bitumen for sound damping, for her current ryzen based PC.

Haha, yes, back in the 90s I had a dual Gigabyte motherboard and two 300Mhz Celerons overclocked to 450. Helped a lot with 3d animation and video rendering, but not much else!

I have overclocked a 1433MHz Athlon 1700+ (TBred/B IIRC) to 2200 MHz (3200+ levels) with an AN7-Ultra.

The secret sauce was running it at 200x11, with 1T capable RAMs, and that thing was snappier than "bog standard" 3200+ systems a considerable amount.

Without much of a voltage bump, and a good cooling solution, it ran within its thermal design without noise, and with rock solid stability. That system lived more than 15 years IIRC.

My favorite OCs were a $250 Black Friday special Celeron laptop that I pin-modded using a few-mm long piece of a single strand of stranded cat5 to go from (IIRC) 1.5Ghz to 2.0Ghz by just shorting two pins on the socket under the CPU, and a 4.6ghz (3.3-3.7ghz stock) Sandy Bridge i5-2500k that was rock-solid on air cooling with a comically large (especially at the time) tower cooler. That latter desktop ran the heck out of Team Fortress 2 (which I still play at least once a week with one of the last remaining community servers, End of the Line Gaming) for many many years.

i had a 1.4ghz Duron i ran stably at 2.45ghz, amazing value

> I still miss HardOCP and Kyle Bennett and his team's reviews.

Kyle stil posts on Hardforum, and much of the team went on to https://www.thefpsreview.com/ but it's not really the same, because there's no 50% overclocking by just moving a jumper. CPUs and GPUs get factory overclocking that's probably within 10% of what you can get with reasonable efforts.

If it comes like that from the factory, is it overclocking? Isn't it just clocking?

potato, overpotato

We live in the age of dynamic clocks where modern performance-oriented CPUs try to optimize both performance and power efficiency at all times, so for the vast majority of users, it's both a lot faster and a lot more efficient to do things this way, while enthusiast parts still allow a lot of manual control to squeeze out the last few percent. I've had really good luck in my past few builds just getting very high-spec RAM and running XMP / DOCP profiles with a small FSB OC and letting the multipliers do the rest.

I have extensive experience in watching LTT's jank cooling videos, and I think water cooling with a big relatively big reservoir would be able to keep the temperature at a chosen temperature. I found someone who has done it: https://www.youtube.com/watch?v=iBNSbzTzfSE&t=20s using this kit: https://www.seeedstudio.com/High-Performance-Liquid-Cooler-f...

The temperature inversion effect is more pronounced at 16nm (Pi 5) than older nodes. This results in high VT cells performing better when warmer, the opposite of what we are used to. At the "normal" operating conditions (temp and frequency), this shouldn't be noticeable but when your at the absolute frequency limit it's not ideal for your critical path (where you normally use HVT cells) to get any slower. Perhaps it's related to this.

Wonder if it was more to do with deltas. Everything at 50° might be more stable then hotspots?

This might be naive but you may take a look at warm water cooling from HPC/ Hyper Scalers. Combined with a custom block this should stay stable at the 50-60° sweet spot.

> but instead 'get it as cold as possible'

More like 'get it as ambient as possible' so if you're in a 50 degree room you're all set.

You've mixed up Celsius and Fahrenheit.

I don't see where anybody in this thread or the linked article said Fahrenheit. Where do you see mixed units?

I find myself disappointed in the lack of helium cooled silicon chips in the modern year of 2024.

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