this post was submitted on 08 Jul 2026
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Science Memes

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[–] stoicmaverick@lemmy.world 53 points 2 days ago (4 children)

Okay, who gets to be the lucky one to calculate the amount of time that thing could heat sink a pegged, modern, 120w TDP CPU before it throttles at 100C? I'll give you a sticker.

[–] resipsaloquitur@lemmy.cafe 44 points 2 days ago (1 children)

Nice try. I’m not googling “copper pegging” again.

[–] Piemanding@sh.itjust.works 17 points 2 days ago (1 children)

That thing doesn't make any sound so you gotta search "Copper Sounding" instead.

[–] JayGray91@piefed.social 3 points 1 day ago (1 children)

I hate that I know what that entails.

[–] stoicmaverick@lemmy.world 5 points 1 day ago

If you want to do it, but don't have a proper sounding rod, you can just use your house key instead.

[–] Contramuffin@lemmy.world 48 points 2 days ago* (last edited 2 days ago) (8 children)

Was intrigued, so made a simulation to figure it out.

TLDR: 592.2 seconds, or 9 minutes and 52.2 seconds. Very similar to the other comment - it appears temperature differentials and heat loss to the air have opposite effects on thermal throttle time and mostly cancel themselves out. For the most part, heat transfer and heat loss appear to affect the thermal throttle time less than the sheer heat mass of the block by several multiples

Assumptions:

  • Copper's heat conductivity is 400 W/m-K, and specific heat is 0.4 J/g-K, and density is 9000 kg/m^3, and these values do not change over the range of temperatures
  • Air's heat transfer coefficient is 20 W/m^2-K and does not change over the range of temperatures
  • The surrounding air does not change in temperature and remains at room temperature (25 C)
  • The input wattage is actually 120 W and not just random marketing bullshit
  • The copper block's size is 4 cm x 4 cm x 16 cm (same as other comment)
  • The temperature within the copper block differs only by the vertical axis; it is assumed that temperature does not change if you move horizontally into the block

Modeling conditions:

  • The block is sliced into 100 equally-sized slices, stacked vertically.
  • Each slice starts off with a temperature of 25 C
  • 120 W is input directly into the bottom slice
  • Heat transfer is modeled between each slice
  • Heat loss into the air is modeled for each slice (top slice has more heat loss due to more contact with the air)
  • Temperature changes are calculated per millisecond
  • Final time is calculated by the total number of milliseconds it takes for the bottom slice to reach a temperature greater than 100 C

Fun facts I found from playing around with the model:

  • According to this model, at the time that the CPU thermal throttles, the top of the block should be 85 C
  • If we assume instantaneous heat transfer, time to thermal throttle goes up to 703 seconds (11 minutes and 43 seconds). Difference is about 2 minutes.
  • If we assume no heat loss to the air, time to thermal throttle goes down to 500.0 seconds (8 minutes and 20 seconds). Difference is about 1.5 minutes.
  • The copper block should be able to prevent throttling as long as the CPU remains idle (30W for AMD CPU's). The CPU should cap out at around 82-83 C.
  • The copper block can prevent thermal throttling for a 170 W CPU for 368.1 seconds, or 6 minutes and 8.1 seconds
[–] stoicmaverick@lemmy.world 17 points 2 days ago

Well goddamn... Ok. Go ahead and dm me your home address, phone number, social and/or tax id number, the name of the street you grew up on, the name of your favorite teacher, the IMEI number of your cellphone, a high resolution set of your fingerprints, and a list of your three greatest fears, and I'll get your sticker sent over as soon as I can.

[–] kunaltyagi@programming.dev 3 points 1 day ago (1 children)

How long a copper block do I need to prevent any throttle?

[–] Contramuffin@lemmy.world 6 points 1 day ago* (last edited 1 day ago) (2 children)

Good question. I had to modify my code to run more efficiently, since not throttling implies that the copper block reaches a steady state with very little temperature changes over time.

But, with the changes, I can say that there is no copper block length that would prevent throttling with a 120 W CPU. It seems the heat transfer within the block is slow enough over such long lengths that you get diminishing returns with longer and longer copper blocks. Here's a graph I made summarizing the different block lengths that I tested

With a 65 W CPU, a 32 cm (double the original length) copper block is sufficient to prevent throttling, but it'll reach steady state at 97 C

[–] Avicenna@programming.dev 7 points 1 day ago (1 children)

Have you considered the possibility that Ea-nāṣir might have been delivering inferior quality copper to you?

[–] Contramuffin@lemmy.world 6 points 1 day ago

Ea-nasir promised that these were good quality copper, and I do not have any reason to suspect otherwise. But I'll have you know, if the copper is of inferior quality, I will make sure to send my messenger to complain. He will not hear the end of it!

[–] Jumi@lemmy.world 2 points 1 day ago (1 children)

Would the result change if the copper block gets wider instead of higher?

[–] Contramuffin@lemmy.world 3 points 1 day ago

Apparently, yes. You can prevent thermal throttling if you expanded the base from 4 cm x 4 cm to 4.5 cm x 4.5 cm, and if you increased the height from 16 cm to 100 cm. The temperature caps at around 97 C.

[–] Bahnd@lemmy.world 9 points 2 days ago

You did the monster math.

Respect.

[–] kahjtheundedicated@lemmy.world 10 points 2 days ago

Respect for taking the time to model that. Goes to show why heat sinks look the way they do, and not just big lumps of metal lol

[–] mnemonicmonkeys@sh.itjust.works 9 points 2 days ago (1 children)

Numerical methods is cheating! Real men use PDE's!

/s of course, though I was kinda hoping you'd use PDE's

[–] Contramuffin@lemmy.world 13 points 2 days ago (2 children)

See, I thought about doing that, but then I realized: I don't actually want to do that

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[–] KSPAtlas@sopuli.xyz 56 points 2 days ago (6 children)

Let's assume the dimensions of the copper block are 40mm40mm160mm (I'm not taking the heat spreader into account here)

That results in a volume of 256000mm3, or 256cm3

Copper (at 20C) has a density of 8.935 g/cm3, so that's roughly 2.28736kg of copper

Copper has a specific heat capacity of 384.603 J/(kg K)

Using E=cm∆t, we can figure out that it would take ≈ 70378J of energy to heat the copper block to 100C, starting at 20C

With a TDP od 120W, that means it would take 586 seconds to heat the block to 100C, or 9m46s

This is probably way off but I was bored

[–] SleeplessCityLights@programming.dev 48 points 2 days ago (1 children)

Your napkin math is the best we have. We will make all decisions based on it.

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[–] Contramuffin@lemmy.world 25 points 2 days ago* (last edited 2 days ago) (7 children)

Hmm, I think at minimum calculus will need to be involved here. Because we can't just assume that the heat is spread evenly in the copper - it'll likely be hotter at the bottom, leading to thermal throttling earlier than expected. On the other hand, there's going to be heat dissipation into the air, which will help cool the block somewhat

Edit: made a program to model heat transfer and heat loss. It seems to only affect final time by a handful of seconds. So actual time in real life is probably somewhere in the ballpark of 10 minutes

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[–] BCsven@lemmy.ca 84 points 2 days ago* (last edited 2 days ago) (12 children)

Till it all gets to temp then it won't do much. It needs some more surface area to convect heat better.

With enough fins you don't need fans.

[–] Zachariah@lemmy.world 94 points 2 days ago

the other option is

only fans

[–] cRazi_man@europe.pub 23 points 2 days ago (2 children)

Would a slow small fan still make a huge difference to the cooling here? Completely passive cooling seems like something that would only make sense in very specific professional environments (like needing an ultra low sound floor in an audiology chamber or recording studio).

[–] fartographer@lemmy.world 74 points 2 days ago (3 children)

I had a roommate who was getting his doctorate in chemical engineering, specifically focused on graphene. He was able to demonstrate how doping the materials in a heat sink to alter their ability to "release" heat, and then organizing these intentional hotspots along the length of the fins, you could create an active airflow using a stationary object.

But then his lab manager killed his grant and instead put him on a project partnered with BMW to make their bumpers more marketable.

[–] Malyca@lemmy.zip 33 points 2 days ago (2 children)

Really makes you wonder how many revolutionary ideas have fallen through the cracks because of moron management

[–] orbituary@lemmy.dbzer0.com 15 points 2 days ago

Black pilled by monetary interests.

[–] Semjeza@fedinsfw.app 6 points 2 days ago (1 children)

Many folks in higher education in the UK have been bemoaning a generation of genii lost to business and the City who put their talents and creativity to the good of making profit rather than inventing and humanity.

Many more have their funding and direction tilted to capital, too.

[–] Aceticon@lemmy.dbzer0.com 4 points 2 days ago

If you're a Mathematical prodigy you either become a Quant making mathematical models for Price and Risk of Over The Counter (so, not sold in a Market) derivatives or, if you have good salesmanship skills, a Trader of such financial instruments.

None of this brings any actual improvement to Mankind but it sure pays well (more the latter than the former) since the way our Economic System is structured and as a side-effect of unbalancing the playing field to make sure the wealthy get ever more wealthy, Money is the thing that makes the most Money, and even just a tiny slice of such flows is far more monetarilly rewarding than almost all other forms of creation or discovery.

[–] Axolotl_cpp@feddit.it 9 points 2 days ago

Who knows how many great ideas we have lost because of bad management and capitalism...sigh

[–] shelf@piefed.social 11 points 2 days ago

That's a shame that sounded really cool.

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[–] Gork@sopuli.xyz 16 points 2 days ago

With big enough copper block it might not matter (like the size of a house, but of the good quality stuff not that shit Ea-Nasir sells).

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[–] aeronmelon@lemmy.world 48 points 2 days ago (1 children)

Toblerone Gaming Heat Sink.

[–] StillAlive@piefed.world 27 points 2 days ago (1 children)

Toblerone has one identifier, its triangular shape. ☝️🤓

[–] ruuster13@lemmy.zip 11 points 2 days ago (2 children)

But there is another.... the convection space between the fins.

[–] EggInDisguise@lemmy.blahaj.zone 37 points 2 days ago (1 children)

I remember when that space was less.... Spacious.

[–] not_IO@lemmy.blahaj.zone 11 points 2 days ago (1 children)

yeah that looks so weird right?

[–] EggInDisguise@lemmy.blahaj.zone 12 points 2 days ago (1 children)

Toblerone has famously been shrinkflating their product for some time.

I remember seeing a comparison post many years ago of a modern one vs one that had been bought years ago and rediscovered in a closet or drawer or something. The older ones had thicker spikes.

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[–] kibiz0r@midwest.social 26 points 2 days ago
[–] Tartas1995@discuss.tchncs.de 8 points 2 days ago (1 children)

This is a beautiful connection between science about the past and science about the present.

[–] mal3oon@lemmy.world 11 points 2 days ago

I give it 9/11. It can use another tower.

[–] Jakylla@jlai.lu 28 points 2 days ago (9 children)

A block of diamond would be even better (copper being at 401 W/mK, Diamond at 3320 W/(mK), almost 10x better)

[–] rockSlayer@lemmy.blahaj.zone 68 points 2 days ago* (last edited 2 days ago) (2 children)

But only 3-5 diamonds are generated per chunk, requires an iron pickaxe, and usually doesn't start appearing regularly until Y level 14.

Meanwhile copper can have up to 16 veins of copper per chunk, requires a stone pickaxe, and appears most frequently at Y=48.

Copper is clearly more accessible for making ore blocks.

Wait a sec, this isn't !minecraft@lemmy.world

[–] kernelle@lemmy.dbzer0.com 21 points 2 days ago

Back to the mines with you, you're yearning

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