macos – M2 MacBook Air aggressively throttles P-cores based mostly on a non-CPU sensor, even when CPU is cool

I am operating a MacBook Air M2 on macOS Tahoe Beta 26.0 (developer beta 4, 25A5316i) and have observed a peculiar and aggressive thermal throttling conduct that makes the system very sluggish underneath sustained load.

The Downside:

When the machine’s case will get sizzling, the system appears to enter a closely throttled state. My monitoring app (Stats) reveals that each one Efficiency cores are successfully shut down: their utilization drops to 0% and their frequency is locked on the lowest state (660 MHz).

This forces all system processes onto the Effectivity cores, which then run at 100% load. The pc turns into extraordinarily sluggish and borderline unusable for something past fundamental operations like textual content modifying.

Here’s a screenshot of the system on this throttled state (Picture 1):

As you’ll be able to see:

• P-cores are at 0% utilization and 660 MHz.
• E-cores are at 100% utilization.
• The Common load is extraordinarily excessive (68.48 over 1 minute).

The Paradox: It is Not Immediately Tied to CPU Core Temperature

My preliminary assumption was that this was normal CPU thermal throttling. Nevertheless, my observations present this isn’t the case. The throttling appears to be triggered by a special thermal sensor, not the CPU cores themselves.

Proof 1: Throttling Happens at Low CPU Temperatures
Here’s a sensor studying from when the machine was within the throttled state described above.

Be aware: I do not know why the Stats app reveals all cores as ‘efficiency core’ on this tab.

• Common CPU temperature is barely 59.3°C, and the most popular core is 61.2°C. These are very protected temperatures.
• Regardless of the cool CPU, the P-cores are shut down as proven within the first picture.

Proof 2: No Throttling Happens at Excessive CPU Temperatures
Conversely, I can push the CPU to its thermal restrict (e.g., with a brief, intense process) with out triggering this particular P-core shutdown, so long as the machine’s chassis hasn’t had time to warmth soak.

• Right here, the CPU cores are operating at over 100°C whereas the machine was nonetheless not throttled.
• The CPU Energy draw is excessive (14.53W) in comparison with the throttled state (0.16W), indicating the P-cores are lively.
• The system stays responsive throughout this time.

This leads me to consider the throttling is a proactive measure based mostly on a chassis, battery, or different part’s temperature, somewhat than a reactive measure to the CPU’s personal temperature.

My Questions:

1. What’s the particular thermal administration mechanism at play right here? Is it a recognized conduct for fanless MacBooks to close down P-cores?
2. Might this be a bug or a very aggressive coverage, presumably associated to the macOS developer beta I’m operating?
3. Is there any method to regulate or disable this particular, preemptive throttling conduct? I perceive the necessity for thermal administration, however the present implementation makes the machine unusable lengthy earlier than the CPU itself is in any thermal hazard.