GMP damaging Zen 5 CPUs?

69 sequin 33 8/27/2025, 4:24:12 PM gmplib.org ↗

Comments (33)

topspin · 56m ago

As there is ongoing drama with Zen 5 and power issues, there are people with the instruments and the motivation to investigate this. You should consider contacting Gamers Nexus, and help them to get your test suite running. They can measure power draw and do a thermal analysis of this CPU, and they'd likely be eager to do it, given the possibility of making a bunch of dramatic YouTube content about design flaws in widely used hardware. That's pretty much their whole schtick in recent years.

> Modern CPUs measure their temperature and clock down if they get too hot, don't they?

Yes. It's rather complex now and it involves the motherboard vendor's firmware. When (not if) they get that wrong CPUs burn up. You're going to need some expertise to analyze this.

fxtentacle · 52m ago

He's a bit sensationalist, yes, but I am thankful that he saved us from buying affected Intel CPUs.

hnuser123456 · 12m ago

GN wasn't the first to break the story the 13/14th gen was defective. The thousands and thousands of users experiencing the issues collectively noticed pretty quick.

spookie · 41m ago

Not sure of sensationalist or just doing great reporting. I take him as one of the last good tech journalists on the platform.

db48x · 27m ago

> The so-called TDP of the Ryzen 9950X is 170W. The used heat sinks are specified to dissipate 165W, so that seems tight.

TDP numbers are completely made up. They don’t correspond to watts of heat, or of anything at all! They’re just a marketing number. You can't use them to choose the right cooling system at all.

https://gamersnexus.net/guides/3525-amd-ryzen-tdp-explained-...

mastax · 1m ago

Enthusiast-oriented motherboards often default enable Precision Boost Overdrive, causing higher power and temperature limits for longer periods. To run the CPU at “stock” you need to go in and disable that. Their default Load Line Calibration might be aggressive as well.

tux3 · 53m ago

The room temperature or precise way the paste was applied should not matter. Modern CPUs have very advanced dynamic voltage and frequency scaling (DVFS), which accounts for several sensors, including temperature.

These big x86 CPUs in stock configuration can throttle down to speeds where they can function with entirely passive cooling, so even if the cooler was improperly mounted, they'd only throttle.

All that to say, if GMP is causing the CPU to fry itself, something went very wrong, and it is not user error or the room being too hot.

mk_stjames · 16m ago

This was my first question as well- I thought it had been a long, long time since you could fry a CPU by taking away the heatsink.

As in... what, AMD K6 / early Pentium 4 days was the last time I remember hearing about cpu cooler failing and frying a cpu?

secabeen · 31m ago

I would be interested to see if they had the same result with PTM7950 thermal material instead of paste. I've seen significantly better temps with these modern phase-change compounds, and they essentially eliminate application errors.

craftkiller · 58m ago

Looking at the AM5 pinout[0], it looks like those pins are VDDCR and VSS. There might be a little bit of PCIe sprinkled in towards the outer edges, but I'm not 100% on the orientation of this pinout vs the orientation of the CPU. I don't know anything about electricity so I've got nothing else to add.

[0] https://upload.wikimedia.org/wikipedia/commons/2/2d/Socket_A...

wrs · 2m ago

[delayed]

FuriouslyAdrift · 18m ago

Most likely it's the motherboard. ASRock is getting nailed right now for unstable XMP and CPU voltages (it's recommended to undervolt a little just in case).

The Asus Prime B650M motherboards they are using aren't exactly high end.

bob1029 · 52m ago

Could be the power supply and load profile?

I've heard some really wild noises coming out of my zen4 machine when I've had all cores loaded up with what is best described as "choppy" workloads where we are repeatedly doing something like a parallel.foreach into a single threaded hot path of equal or less duration as fast as possible. I've never had the machine survive this kind of workload for more than 48 hours without some kind of BSOD. I've not actually killed a cpu yet though.

bee_rider · 42m ago

Is that, like, an intentional stress-test for the hardware that you’ve come up with?

fxtentacle · 54m ago

"We suspect that GMP's extremely tight loops around MULX make the Zen 5 cores use much more power than specified, making cooling solutions inadequate."

I feel like if this was heat related, the overall CPU temperature should still somewhat slowly creep up, thereby giving everything enough time for thermal throttling. But their discoloration sure looks like a thermal issue, so I wonder why the safety features of the CPU didn't catch this...

jeffbee · 46m ago

Are we talking "slowly" in a relative sense? A silicon die of this size has a thermal mass (guessing) around 10⁻³ J/K but a power dissipation rate over 200W, so it can rise from room temperature to junction temperature limits almost instantly.

topspin · 42m ago

People without a background in electronics don't appreciate what modern CPUs and GPUs are doing: the amount of current flowing through these devices is just mind blowing. With adequate cooling, a Ryzen 9 9950X is handling somewhere in the neighborhood of 150-200 amps under high load.

nisegami · 18m ago

I initially scoffed at the 150-200 amps. But I know core voltage is usually in the neighbourhood of 1V so to draw 200W, you really would have to basically be moving 200A of current. That's wild.

nromiun · 38m ago

How is that possible? Even if the chip did not get enough cooling it should have been just throttled heavily.

tliltocatl · 9m ago

Maybe the throttling circuitry/firmware simply doesn't have enough time to react.

jsheard · 17m ago

Modern silicon is so dense and heats up so fast that throttling is easier said than done. I think they have to model and predict the thermals nowadays, because by the time they could react to a temp sensor spiking the chip could already be toast.

tw04 · 49m ago

That looks like a combination of improperly mounting the heatsink and noctuna being wrong in their recommendation to offset it. I’d imagine for gaming cooling one side more makes sense but my completely uneducated guess is that GMP is working a different part of the CPU than gaming does.

toast0 · 39m ago

They had failures with standard mounting and offset mounting.

Also, take a look at a delidded 9950; the two cpu chiplets are to one side, the i/o chiplet is in the middle, and the other side is a handful of passives. Offsetting the heatsink moves the center of the heatsink 7mm towards the chiplets (the socket is 40mm x 40mm), but there's still plenty of heatsink over the top of the i/o chiplet.

This article has some decent pictures of delidded processors https://www.tomshardware.com/pc-components/overclocking/deli...

jsheard · 46m ago

This is what Zen5 looks like under the IHS: https://i.imgur.com/j85YUzX.jpeg

Everything is offset towards one side and the two CPU core clusters are way towards the edge, offset cooling makes sense regardless of usage.

tester756 · 55m ago

My Ryzen CPU recently died too! wtf

FuriouslyAdrift · 17m ago

ASRock motherboard?

fithisux · 25m ago

I thought that it was an Intel only problem.

What kind of sh..t are they pushing on us?

Even if Raspberry seems slow it gets more and more attractive.

The x86-64 ISA is a POS BTW.

It needs major refactoring. The backwards compatibility is killing the platform.

dkiebd · 1h ago

Photos so bad it made me wonder if this was posted in 2025 or 2005.

internetter · 25m ago

Photos taken by engineer, not photographer.

dkiebd · 19m ago

What kind of camera is using the engineer that doesn't have autofocus and generates 378x283 photos?

on_the_train · 17m ago

What is gmp?

gus_massa · 3m ago

From https://gmplib.org/#WHAT

> What is GMP?

> The GNU Multiple Precision Arithmetic Library

> GMP is a free library for arbitrary precision arithmetic, operating on signed integers, rational numbers, and floating-point numbers. There is no practical limit to the precision except the ones implied by the available memory in the machine GMP runs on. GMP has a rich set of functions, and the functions have a regular interface.

Many languages use it to implement long integers. Under the hood, they just call GMP.

IIUC the problem is related to the test suit, that is probably very handy if you ever want to fry an egg on top of your micro.

beezle · 1m ago

At first I thought it was Green Mountain Power ;)

kgwgk · 10m ago

The domain has the answer: https://gmplib.org/

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GMP damaging Zen 5 CPUs?

Comments (33)