Dell Precision 3280 Compact — intermittent CPU power-limit jumping between two values...

Disclaimer: I'm not very familiar with some of the low-level terms like "MMIO" and so on, so I asked AI to help me analyze and collect data, but the description is written by me (human)...

Summary

I noticed my 3280 compact seems to randomly jump between two states (without any change in settings either in the BIOS nor OS, power is always set to "optimized" in BIOS instead of "quiet"), power mode set to "balanced" in OS (Ubuntu). In one state, it would be completely capped at 80W; in another, it would start at around 154 W (for around 30 s), then stay at 100 W for another 20s, and finally stablize at 80W. And unfortunately it seems to randomly jump between two states between reboots without any change to any settings...

Tests were done both via `stress-ng --cpu 0 --cpu-method matrixprod --timeout 600s` alone, no stress on GPU or other components. Power monitoring is done via `sudo btop` (without sudo it wouldn't be able to read power data).

It happens both for my 280 W adapter (LA280PM230) and another 240 W adapter (LA240PM190).

SYSTEM

Model: Dell Precision 3280 Compact
CPU: Intel Core i5-14500

GPU: NVIDIA T400 4G
BIOS: 1.26.0
OS/kernel: Ubuntu 26.04, Linux 7.0.0-29-generic

Data collected with help of AI when system is in "uncapped" state with 280W adapter:

```

Dell ACPI platform profile: balanced
Available ACPI profiles:     quiet, balanced
Ubuntu power profile:        balanced

Intel CPU controls:
  intel_pstate status:       active
  no_turbo:                  0 (turbo enabled)
  max_perf_pct:              100

RAPL limits exported by Linux:
  /sys/devices/virtual/powercap/intel-rapl/intel-rapl:0
    long_term:                200000000 uW (200 W), window 31981568 us
    short_term:               154000000 uW (154 W), window 2440 us

  /sys/devices/virtual/powercap/intel-rapl-mmio/intel-rapl-mmio:0
    long_term:                100000000 uW (100 W), window 31981568 us
    short_term:               219000000 uW (219 W), window 976 us
    peak_power:               212000000 uW (212 W)

No active Linux CPU cooling throttle was present:
  intel_powerclamp=0
  Processor cooling devices=0

```

In the "80W" state:

So my question here is:

- which state is the "expected" behaviour?

- if both are "expected", how should I switch between them?

- If only one should be allowed, guess there is some issue somewhere?

Feel free to ask me to provide more details if any is missing.

Thanks!