My iMac is now so slow as to be almost unusable.
It’s a 2013 iMac Intel (21.5-inch, Late 2013) 3.1 Ghz Intel Core i7 with 16 GB Ram and 1TB disk. (regular hard drive)
Symptom is that over time the Mouse gets unresponsive, jerky movement and impossible to see on the display in a smooth motion so very hard to use. I am mouse oriented don’t use many keyboard shortcuts at all as I’m faster with a mouse. I use a Dynex wireless mouse but I’ve tried with several different Logitech mice and even a wired mouse. I hate the Apple mice so I’ve never used them. Then even simple things like opening files and moving stuff gets slow and eventually it can take forever to do a simple task. The system takes between 8-15 minutes to boot up and about 5 minutes to shutdown. Safari gets to acting odd with solid black pages that only start to display the contents if I scroll over them and try to highlight them. Sort of a black screen encryption system I guess Time machine can take hours to do a backup whether it’s my external hard drive or to our Synology NAS server. I typically disable Time Machine during the day and let it run overnight to catch up. I do run a nightly CCC backup to an external drive. It can take between 2-6 hours to run.
If I leave it up for very long, over several days, it will crash with a kernel panic.
Rebooting will usually but not always help for a while.
I’ve run it in SAFE mode for a day and by the end of the day it was having the same problems.
I’ve run a full disk first aid on the internal hard drive and no issues were found at all.
I’ve run Clean My Mac on it and cleaned out all the various old software, no viruses found and nothing showing up on that scan.
Hard drive has about 130-140GB available.
I can run Activity monitor and the only thing taking lots of CPU is Activity Monitor itself and the kernel_task generally CPU is about 95-96% idle. Checking memory no swap memory is in use and typically only about 8 GB in use. Checking disk mds_stores has the most data moved at around 6GB.
I have not yet tried as another user as I need to move a lot of my data files if I plan to actually use it during that test. That was going to be my next step.
I’m running Catalina 10.15.7
By way of reference my Mac Air MacAir (13.3 inch ) 1.6GHz dual-core Intel Core i5 with 16GB Ram 1TB disk also running Catalina 10.15.7 works just fine. I’ve done most of the same types of tasks on it and it also is doing time machine to an external spinning hard drive and to the server but never bogs down nor crashes.
After the another user test (which I hope to complete today) I was thinking first try to reinstall Catalina. Then I was guessing a nuke and pave but that’s going to be nearly a week of work and I’m wondering if I should try something else first.