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GMP damaging Zen 5 CPUs?

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Re: GMP damaging Zen 5 CPUs?

#11

Post by jeffbee »

fxtentacle wrote: post #6

"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 C…

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.

Re: GMP damaging Zen 5 CPUs?

#12

Post by jsheard »

tw04 wrote: post #10

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.

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.

Re: GMP damaging Zen 5 CPUs?

#13

Post by bee_rider »

bob1029 wrote: post #9

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 with…

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

Re: GMP damaging Zen 5 CPUs?

#14

Post by topspin »

jeffbee wrote: post #11
fxtentacle wrote: post #6

"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 C…

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.

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.

Re: GMP damaging Zen 5 CPUs?

#15

Post by spookie »

fxtentacle wrote: post #8
topspin wrote: post #4

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 wi…

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

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

Re: GMP damaging Zen 5 CPUs?

#16

Post by toast0 »

tw04 wrote: post #10

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.

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...

Re: GMP damaging Zen 5 CPUs?

#18

Post by secabeen »

tux3 wrote: post #7

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 sa…

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.

Re: GMP damaging Zen 5 CPUs?

#19

Post by db48x »

> 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-...

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