high cpu usage before user login

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Level 1

8 points

high cpu usage before user login

Is there a way to log the system activities, such as errors or cpu usage data, before user login?

I'm using macOS Big Sur 11.0.1 on MacBook Pro 16 inch - 2019. I found the machine is hot and the fan runs at high speed at the login screen, indicating a high CPU usage. This situation continues forever until I logged in, at which time the fan slows down significantly, and the cpu usage is at normal level (below 3%). So everything is fine once logged in.

I guess there should be some abnormal process(es) consuming huge amount of cpu when at the login screen, but I couldn't find any logs during that period because the system log I found starts only after login.

Any helpful information/clues will be appreciated!

MacBook Pro 16″, macOS 11.0

Posted on Nov 22, 2020 3:09 PM

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Answer 1

nbotros

Community Specialist

Nov 30, 2020 4:21 PM in response to ruib100

Hello ruib100,

Welcome to Apple Support Communities. We understand the concern with the behavior you're experiencing with your Mac's CPU, and fan at the login screen, and we'd be happy to look into this with you.

To get started, please check out these helpful links:

View energy consumption in Activity Monitor on Mac

About fans and fan noise in your Apple product

Also, let's try to reset the SMC, and see if that makes any difference:

How to reset the SMC of your Mac

We hope this information is useful. Kind regards.

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Answer 2

ruib100 Author

Level 1

8 points

Nov 30, 2020 7:07 PM in response to nbotros

Hello nbotros,

Thank you for your tips. These are useful tips.

However in my weird case, since everything goes back to normal as soon as login, neither the activity monitor nor the system log is able to provide any relative information regarding that overheating before login.

The Apple support told me to reset SMC, NVRAM, enter safe mode, and reinstall macOS, but unfortunately none of them worked. The next step should be factory reset and physical check, but since the behaviour doesn't have an effect after login, and since it appears somewhat like a software bug, or even a normal behaviour related to the newly upgraded OS, so I decided to wait for the next software update as well as more info from the forum.

Thank you for you response anyway,

Best

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high cpu usage before user login

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