[adrian_b]

The small coolers used by them are not recommended by Noctua for 9950X. Noctua recommends only bigger coolers for 9950X, which dissipates 200 W permanently on a workload like theirs (which is much less than the over 250 W dissipated in similar conditions by the competing Intel CPUs).

Despite this, the overtemperature protection of the CPUs should have protected the CPUs and prevent any kind of damage like this.

Besides the system that varies continuously the clock frequency to keep the CPU within the current and power consumption limits, there is a second protection that stops temporarily the clock when a temperature threshold is exceeded. However, the internal temperature sensors of the CPUs are not accurate, so the over-temperature protection may begin to act only at a temperature that is already too high.

So these failures appear to have been caused by a combination of not using the appropriate coolers for a 200 W CPU, combined with the fact that AMD advertises a 200-W CPU as an 170-W CPU, fooling naive customers into believing that smaller coolers are acceptable, and with either some kind of malfunction of the over-temperature protection in these CPUs or with a degradation problem that happens even within the nominal temperature range, but at its upper end.

[ollien]

> 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

[adrian_b]

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 with turbo enabled.

With "best turbo headroom", you can be certain that the CPU can run all-core intensive tasks with turbo enabled. Even if you do no overclocking, but you run all-core intensive tasks with turbo enabled, this is the kind of cooler that you need.

Noctua does not define what "medium headroom" means, but presumably it means that you can run with turbo enabled all-core tasks that have medium intensity, not maximum intensity.

There is no doubt that it is a mistake to choose such a cooler when you intend to run intensive multi-threaded computations. A better cooler, but not much bigger, like NH-U12A, has an almost double cooling capacity.

That said, there is also no doubt that AMD is guilty of at least having some bugs in their firmware or in failing to provide adequate documentation for the motherboard manufacturers that adapt the AMD firmware for their MBs.

[ollien]

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