I have an "old" late 2015 iMac 21,5" that I want to use for photography in the studio (for quality control). But even when it was new it wasn't the fastest because of the slow CPU and no SSD.


  • macOS Catalina 10.15.7
  • 21,5", late 2015
  • 1,6 GHz Dual Core i5
  • 8 GB Ram
  • HDD
  • Intel HD 6000 1536 MB

My question is, when I upgrade to Monterey, will I get a performance boost? Or will it get even worse? I've read that newer macOS is more optimized also for older machines. Is that true?

When I google for it I only find ways to install new macOS on unsupported devices. But this iMac is one of the last that is supported.

Even open the settings app is super laggy. Currently I can work with it somehow, but it could be better.

  • 4
    What makes those iMacs so slow is the old spinny rust hard drive. Swapping up to an SSD will bring it to life, whatever OS you put on it.
    – Tetsujin
    Commented Jan 25, 2022 at 11:22
  • 1
    Even an external SSD as boot drive via USB 3.0 will give you an extreme performance boost.
    – X_841
    Commented Jan 25, 2022 at 11:33
  • Yes, I thought the same, of course an SSD will speed things up a lot. But my question goes more in the direction like: Is the new macOS version more "bloated" and will slow down that small CPU even further or is it even optimized for these low performance macs?
    – jona
    Commented Jan 25, 2022 at 11:37

1 Answer 1


There's no universal answer to that question. It depends on your workload, which applications you use, what you use them for, how often and to what extent, etc.

You could make a backup of your complete system - upgrade and test your new system. If you do not like the new system, you can roll back using the backup.

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