Mac Mini 2018 sudden unexplained performance issues

Question

I have a 2018 Mac Mini i7 with 32gb Ram. I have been having strange performance issues lately. I decided to reinstall the OS but it's still happening. I think I noticed the problems initially when I installed Mac OS Ventura. So I decided to revert to Monterey but the issue is still happening. It could have something to do with some random update, I'm not sure. The problem is that everything is suddenly slow and laggy. Trying to watch a movie in Preview is suddenly choppy. Trying to load a Windows 11 or Windows 10 VM is painful. Everything used to be so quick, now it's so slow.

I was thinking it could be a hardware issue, but i'm not even sure where to look. The CPU isn't maxed and nothing seems to be out of the norm. Everything is just... slow.

I am 95% convinced that it is some OS update, but again, I have no idea where to even start looking.

Thanks

Answer 1

Here are some fairly generic steps for trouble shooting performance issues.

1. Keep Activity Monitor running, and see if anything is using large amounts of CPU or memory when the slowness occurs.

   If 'kernel_task' is using lots of CPU, then that would suggest that your Mac is overheating, which might be caused by a build-up of fluff inside.

2. Test running the Mac in Safe Boot mode, and then in a brand new user account.

   Safe Boot mode will (amongst other things) exclude any third-party software from loading at boot. You should check that all 'background processes', such as LaunchAgents (found in the /Library and user ~/Library folder of the same name); also Login Items in System Settings.

   A brand new user account will also exclude user-configured Login Items; as well as other configurations that might possibly cause a problem.

3. Verify the disk in Disk Utility. More likely with mechanical hard drives than modern SSDs, but make sure that the disk is working correctly.

Answer 2

One possible reason is CPU thermal paste has dried up resulting in high cpu temperature. In this scenario, CPU will get throttled. Can you check CPU temperature? If CPU temperature is high, try replacing thermal paste on CPU.

Here’s how to check Mac temperature with Terminal:

1. Open Terminal via Spotlight
2. Type the following command: sudo powermetrics --samplers smc |grep -i "CPU die temperature"
3. Enter your admin password
4. Hit Return and wait a few seconds
5. Check CPU die temperature — it will keep refreshing in real time.

Answer 3

This question is old but I had a similar problem with my 2018 Mac Mini. The symptoms were that my mac mini was slow and the fan was constantly on for 2 weeks (verified by istats). The problem ended up being the dust inside and near the vents. I just blew off all the dust and the machine was back to normal again.