i9-14900k reaching 100ºC and thermal throttling 1-2 seconds into a stress test, immediately cools back after

Hi,

I just assembled my PC and started testing things. Hardware specs:

  • CPU: i9-14900K
  • Motherboard: ASUS ROG MAXIMUS Z790 DARK HERO
  • Cooler: ARCTIC Liquid Freezer II 360 A-RGB
  • RAM: Kingston FURY 64GB KIT DDR5 6000MHz CL32
  • GPU: GIGABYTE GeForce RTX 4090 GAMING OC 24G
  • PSU: Corsair HX Series HX1200 - 1200W

When I run CPU-Z "Stress CPU" on 32 threads and watch CPU temperatures in HWMonitor they almost immediately shoot up to 100C. When I stop the test they drop down to 35-40C within 1-2 seconds, here's what it looks like https://imgur.com/a/dya2xt6

When I look at this in Intel Extreme Tuning Utility it does almost immediately show Thermal Throttling: YES, as seen here https://imgur.com/a/xoBwuwq

Now I understand this CPU draws a lot of power and runs hot. I'm just surprised it goes to 100C within just a few seconds.

Running single-threaded benchmarks doesn't really cause it to heat up. Limiting number of threads in CPU-Z is similar. For example running a stress test with limited number of threads:

  • 4 threads: temp at around 85C with no throttling even if it runs for a while.
  • 6 threads: temp around 86-87C, no throttling
  • 8 threads: immediately spikes up to 100C and starts throttling, then goes down, stops throttling, then back up, and repeat with a cycle around 5 seconds

I also tried CPUMark and the scores seem reasonable, tho these benchmarks are quite fast so I'm not sure if they're affected by throttling that much.

Googling around it seems some people are having similar issues, and some suggest the pressure plate for LGA1700 and saying it fixed their issues.

I used Noctua NT-H2 thermal paste, used the cleaning pads, removed the plastic from the cooler, watched a tutorial before, etc. I'm not super experienced but it's probably my 4th or 5th time installing a CPU, so I feel like I've probably done that part correctly, but of course not sure.

Lastly, looking at https://www.intel.com/content/www/us/en/products/sku/236773/intel-core-i9-processor-14900k-36m-cache-up-to-6-00-ghz/specifications.html they say max turbo power is 253W, while intel XTU says "Package TDP: 304W", but that still seems within reason for the Arctic Freezer 360 II, where various tests (e.g. https://www.tomshardware.com/reviews/arctic-liquid-freezer-ii-360-argb-review) say around 290W.

Is there something obvious I'm missing? I've seen so many mentions of "liquid cooling can absorb spikes of heat", but that goes a bit against the "throttles within 1-2 seconds" unless I'm misunderstanding something.