I had the same MacBook Pro 16" i9, the cooling system is definitely not capable to run the CPU at full load without throttling, even if you set the fans to highest speed manually and try to cool the case with a "notebook cooler", it's nothing about dust.

 

Yes, that sounds perfectly understandable – you're addressing a well-known problem that many users of the 16-inch MacBook Pro with Intel Core i9 (especially the 2019 model) have complained about. Back then, Apple tried to pack a lot of power into a relatively thin chassis, and although they improved the cooling system compared to its 15-inch predecessor, it's simply not enough to truly handle the i9's thermal requirements under sustained load.

Even with tools like Macs Fan Control or smcFanControl, which allow you to set the fans to maximum speed, thermal throttling often occurs after a short time. As you say, this isn't necessarily due to external factors like dust or poor maintenance, but rather to a fundamental design limitation.

Here are a few technical points:
The i9-9880H or i9-9980HK (depending on the model) can get very hot under load – TjMax is around 100°C.
At just 90°C, the system begins to reduce its clock speed to keep temperatures under control.

The cooling solution simply can't keep up with continuous load (e.g., rendering, video conversion, longer compiler runs, etc.).
In addition, Intel CPUs of that generation are quite inefficient compared to Apple's later chips (M1, M2, M3, etc.).

This has prompted many to either switch to the M series or, if they rely on Intel, to opt for more powerful and better-cooled Windows laptops.

Source: AI

 

Interesting convo.

I would examine why it's getting so worked up. I've found my less powerful mbp2018 13" 250gb 16bgram really gets annoyed if I don't have at least 20gb of free memory on disk, especially with external drives connected. Spotlight can take it upon itself to reindex tb's of data. I think I may have blocked this. Also, are you connecting to an external monitor?