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GMP damaging Zen 5 CPUs?

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Re: GMP damaging Zen 5 CPUs?

#231

Post by einpoklum »

kllrnohj wrote: post #216
einpoklum wrote: post #199

Earlier quoted context omitted.

> For what, exactly? TDP stands for "thermal design power" The chip is not designed for this rate of power dissipation; and it is not the rate of power dissipation that you can expect to get from the chip.

> The chip is not designed for this rate of power dissipation Says who? AMD advertises the chip as having a base clock of 4.3 GHz over all cores. The 9950X pulls somewhere around 220W at 5ghz all cores and with how power scales, 170W at the advertised 4.3 GHz seems more than plausible. Seems perfectly within reason that the advertised frequency and the advertised TDP are aligned. I wish Anandtech was still around as…

> Says who?

Says AMD and says Intel, apparently. At the link, there is an official explanation (sort of) how the TDP figure is derived.

Re: GMP damaging Zen 5 CPUs?

#232

Post by menaerus »

db48x wrote: post #225
menaerus wrote: post #217

Earlier quoted context omitted.

https://www.usenix.org/system/files/conference/cooldc16/cool... uses 84W TDP-rated Haswell-architecture Intel i7-4770, and authors constructed the synthetic microbenchmark with 1.67 IPC FPU and 3.86 IPC integer workloads. Then they use RAPL (Running Average Power Limit), something I learned that exists as of today, to measure the power usage on the level of the whole chip package. Reported numbers are ~22W. Consideri…

They didn’t measure 22W, they measured 6W + 22.1W + 4.9W + 1.8W + 4.8W + 11.2W = 50.8W. Add in 66.3W for the other three cores and that would be 117.1W. Benchmark #2 measured a few watts less than that. But they don’t give the IHS temperature so you could repeat the exact same experiment using the same hardware and get different numbers simply because your cooling setup was better or worse than theirs.

My understanding, and per Intel documentation, is that RAPL is giving them power consumption over the whole package therefore I believe 22W for Cores (W) in their figure is correct? Other figures such as instruction decoder they seem to extrapolate from that figure since RAPL doesn't and can't give information on that level of granulation? I could be wrong but that's how I interpret their data and why I think the date is not to be accumulated together.

As per cooling setup, I think I agree. This is something that I didn't know but it makes sense.

Re: GMP damaging Zen 5 CPUs?

#233

Post by fc417fc802 »

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…

I experienced that with a GPU years ago. A workload I wrote caused a pronounced high frequency noise from the card that I've never encountered the like of before or since. I'd describe it as a very high frequency chirping. I refactored the program rather than seeing what would come of it.

Re: GMP damaging Zen 5 CPUs?

#234

Post by db48x »

menaerus wrote: post #232
db48x wrote: post #225

Earlier quoted context omitted.

They didn’t measure 22W, they measured 6W + 22.1W + 4.9W + 1.8W + 4.8W + 11.2W = 50.8W. Add in 66.3W for the other three cores and that would be 117.1W. Benchmark #2 measured a few watts less than that. But they don’t give the IHS temperature so you could repeat the exact same experiment using the same hardware and get different numbers simply because your cooling setup was better or worse than theirs.

My understanding, and per Intel documentation, is that RAPL is giving them power consumption over the whole package therefore I believe 22W for Cores (W) in their figure is correct? Other figures such as instruction decoder they seem to extrapolate from that figure since RAPL doesn't and can't give information on that level of granulation? I could be wrong but that's how I interpret their data and why I think the dat…

Right, RAPL just reports a total power usage figure for the whole CPU. The authors then develop a model which they believe splits that total into multiple components that correspond to parts of the CPU. This is possible because CPUs provide performance counters that measure what the CPU is actually doing. For example if you write programs that are very similar but have different ratios of cache hits and misses then they’ll draw different amounts of power. You can use those differences to devise a formula for the amount of power used by the cache.

And indeed, they give their formula in section 4.2:

    P_package = 6.05 + cycles/second × 1.63×10⁻⁹
                     + μops issued/second × 2.15×10⁻¹⁰
                     + μops decoded/second × 1.40×10⁻¹⁰
                     + L1 hits/second × 4.35×10⁻¹⁰
                     + L2 references/second × 4.05×10⁻⁹
You can see that the power used by the whole package is the sum of six terms. The values that the calculated for those six terms for each of their benchmarks are given in table 4. The 22W figure for the core(s) is just based on the frequency the CPU is running at.

Re: GMP damaging Zen 5 CPUs?

#235

Post by marshray »

mrheosuper wrote: post #209
marshray wrote: post #140

Earlier quoted context omitted.

Clearly paste was squeezed out from the entire perimeter of the CPU. Offset mounting is used intentionally for this CPU. Probably there's less paste remaining on the south end of the CPU because that's where the mounting force is greatest. If anything, there's too much paste remaining on the center/north end of the CPU. Paste exists simply to bridge the roughness of the two metal surfaces, too much paste is a bad sig…

Many reviewers have tested that too much paste is not an issue, except being messy to clean.

The experiments comparing different paste and application methods I've seen only make 1-2 degree C difference. Which enthusiasts might care alot about, but most people wouldn't notice.

Re: GMP damaging Zen 5 CPUs?

#236

Post by edgineer »

Gracana wrote: post #223
edgineer wrote: post #179

"We don't overclock or overvolt or play other teen games with our hardware." You overclock as a teen so that as an adult you know to verify your CPU's voltage, clock speeds, and temperature at a minimum when you build your own system. They made no mention of monitoring of CPU temperature, ECC corrected/detected errors, or throttling. They then ran CPU benchmark loads for several months on the system. "The so-called T…

CPUs with stock cooling solutions will turbo boost up to max temp and stay there, that's completely normal and shouldn't cause a CPU to physically burn up, even if you do it for months.

"boost up to max temp and stay there"

At stock settings CPUs will boost depending on many factors. Once one of several different limits is hit the CPU will not boost as high, trying to find a steady state where it stays below Tjmax.

Note the following: the 9950x does not come with a stock cooler. AMD recommends water cooling for the 9950x. Transistor lifetime decreases exponentially with temperature.

I'd expect that a 9950x under sustained load paired with a "165W" cooler would not only not boost, but would throttle to below base clocks.

In the case of CPU cooling, I don't agree that relying on the CPU's thermal safety nets to continuously regulate the system to avoid damage is good practice. With additional cooling to ensure it never reaches Tjmax, this also will result in better CPU performance, a tangible benefit.

Had the author monitored his systems, he would have observed high temperature and throttling. Yes, in 2025 it's arguable that a CPU's safety net should be reliable wrt temperature, even if you run with no heatsink at all. I also agree that TDP specifications are unclear.

But the bottom line is that you should pay the extra $100 or so to cool your CPU properly. It will be faster and more reliable.

Please take care of your equipment; do not take it for granted.

Re: GMP damaging Zen 5 CPUs?

#237

Post by spoaceman7777 »

ndiddy wrote: post #213
dukezzz wrote: post #203

Earlier quoted context omitted.

Noctua recommends mounting their cooler so that the center is shifted toward the lower part of the CPU. From your picture with the thermal paste, it’s clear that your cooler is only making contact with about two-thirds of the CPU, meaning you mounted it incorrectly. The cooler’s contact area must always cover the entire CPU; otherwise, you reduce heat transfer capacity. On top of that, you’re already using an undersi…

Welcome to Hacker News! I'm glad my comment encouraged you to join the site. I didn't write the article, I was just commenting because other users seemed to miss information that was written in it. The picture with the thermal paste shows that paste was squeezed out from the entire perimeter of the CPU, so the cooler is making contact with the whole CPU. The paste is squeezed thinner near the lower side of the CPU be…

i'm not sure what image you're looking at, but the picture in question here most certainly shows a CPU that did not have a properly mounted heatsync (to a very severe degree)

Re: GMP damaging Zen 5 CPUs?

#239

Post by ac130kz »

ASRock has Zen 5 CPUs dying with stock settings from brief core voltage spikes on idle (max core frequencies). I believe either PBO has to be enabled to allow undervolting headroom or VSOC has to be permanently fixed to a value lower than 1.2V.

Re: GMP damaging Zen 5 CPUs?

#240

Post by ollien »

adrian_b wrote: post #214
ollien wrote: post #207

Earlier quoted context omitted.

> The small coolers used by them are not recommended by Noctua for 9950X Noctua's CPU compatibility page lists the NH-U9s as "medium turbo/overclocking headroom" for the 9950X [0]. I don't think it's fair to suggest their cooler choice is the problem here. [0] https://ncc.noctua.at/cpus/model/AMD-Ryzen-9-9950X-1831

That means pretty much "not recommended". On the same page linked by you, Noctua explains that the green check mark means that with that cooler the CPU can run all-core intensive tasks, exactly like those used by the gmplib developers, only at the base clock, which is 4.3 GHz for 9950X, with turbo disabled in BIOS. Only then the CPU might dissipate its nominal TDP of 170 W, instead of the 200 W that it dissipates wit…

It is important to remember that CPUs scale their turbo with thermals. It's not a matter of needing to turn turbo on and off
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