Really slow 2017 iMac 21.5" after fresh install

[Ian]

I don't know a huge amount about Macs, but I'm fixing someone's 2017 iMac as it was unusably slow. It's only a few years old, but it came with a 1TB SATA drive rather then an SSD, which I imagine must be the main culprit. However... it's SO slow - enough that I can't imagine it would ever have been sold like this.

It's running a clean install of Big Sur, so perhaps it's just that the latest OS has higher requirements than whatever it came with in 2017.

I did try installing the OS to an external USB-C SSD, however it has been less reliable when doing this (occasionally tries to boot from the internal SATA instead, or occasionally crashes). It is faster though, but still far from what I'd expect.

Any iMac users here familiar for things I should check? I've done a full drive and memory diagnostic and the current install only has a few additional apps installed from the clean start.

 

[muckshifter]

Memory?

 

[Abarbarian]

https://developer.apple.com/forums/thread/651399

Just giving an update, might help some people

I upgraded from Catalina to Big Sur and had the same slowness that everyone here is complaining about. I have a late 2015 iMac with a fusion drive. At the suggestion of Apple support I created a new user with admin rights and started transferring all data from the existing user to the new user. This was a real pain but I think it's easier than doing a complete new install

It's now a month in and I see no issues, my mac is as fast as it always was with the new user. When I try to login with the old user I still have the same slowness. Just for reference I'm a software developer and sometimes have multiple cpu/memory intensive applications open at the same time. Right now I have Eclipse, Intelij, a tomcat instance and a SQL server on docker (don't ask...) running with no issues!

Have you not got Google up there int norf of uk

Why not put ssd in the mac ?

Install MX-19.

The mac is three years old why have they not bought a newer model ?

 

[Ian]

8GB of memory and tests check out OK. I think it must simply be that the slow HDD can't handle the OS running well, as the external SSD is running well now for some reason.

Had a good google for suggestions, but still the same problem after trying lots of ideas, but I've not tried creating a 2nd user account yet. I guess as it's linked to iCloud, a problem could have migrated across with the fresh install. Will try this tomorrow on the HDD.