Slow 2015 iMac - Need Help

Hi gang,

Thanks in advance for any input here. I have a work owned 27" iMac that has become extremely slow. This happened a few years back and I upgraded the RAM, but the best I’ve got from my IT guy is 1) they don’t support a lot of the apps MPUsers like to have installed (freaked out about CleanMyMac X), and 2) it’s likely Dropbox that is slowing down my machine…

I’m wondering if you all could provide what steps you might take on a work machine to try to get this thing more usable.

Specs: iMac (Retina 5K, 27-inch, Late 2015)
Processor: 3.2 GHz Intel Core i5
Memory: 24GB 1867 MHz DDR3 (2 4GB + 2 8GB)
HD: 155GB left on 1TB

Would welcome ANY other tips, however obvious they may seem to you. THANK YOU!


What’s the storage? All SSD or Fusion Drive?

Maybe you ought to just let them buy you a new one :grinning:

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I’d create a new user & login to a clean OS & diagnose from there. I have the same machine at work with less RAM & when I was last there (in February!) it was still blazing fast.

with +/- 140 GB in Dropbox btw


Yea, you’ll want to diagnose if it’s hardware, the os, or software. People have recommended different ways to help you figure out. I would also recommend looking at activity monitor to see if you’re using up a lot of the CPU or ram.

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I have one from the same generation (i7, 24 Gb of RAM) and I’m a heavy Dropbox user. This machine is still very fast and works very well under Big Sur, so it’s not Dropbox.


To me, it sounds like your drive is having difficulty, and the first order of business is ensuring you have good backups. I would caution against making all new backups over all your old backups, as you want to retain some old backups in case files have recently become corrupt.

I don’t think dropbox is the culprit, but you can pause dropbox syncing to confirm. Work you do will be written to your local drive, but not synced to the cloud.

But again, the first order of business is your backups.


I have exactly the same machine. With the fusion drive. Was using mostly as storage and backup for dropbox and iCloud until covid. I have been using heavily again now since March. I also use dropbox and it does take up resources. That being said, the only time I find dropbox running slowing is on a reboot or fresh start. A spinning hard drive takes a long time to match files on startup from the cloud. Once synced it runs well.

I also get the beachball when accessing files that I have not used in awhile and that, obviously is the fusion drive doing what it was meant to do.

Lastly, when I took the machine up to Catalina I had a failure and decided to reinstall clean. I keep everything personal in iCloud and all work in dropbox so basically there was no data to be lost in doing that. What it did do was eliminate a lot of very old cruft. My first Mac was probably from 2008 and I probably just kept going until that failure two years ago. It sure freshened the machine. I have debated putting SSD in it but I don’t want to deal with the glue.

Long story short. Fresh install can be amazing.

I’ve seen instances where Dropbox gets into a state where it’s constantly syncing and takes a lot of resources. The solution that Dropbox Support offered was to unlink and relink Dropbox (via the Account tab in Dropbox Preferences). Worked like a charm.

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It is whatever came standard on the machine which I believe is the Fusion Drive. Was just a standard machine out of box with those RAM upgrades. Thanks @ismh!

@jec0047 - Trust me I’m working on that :slight_smile: There are grants widely available to faculty, and I’m due for an upgrade this year. Just seems like this is a fixable solution for the interim if I can figure out the problem.

@dfay + @Scout - I’m not super familiar with how to load up a clean OS. I’ll Google it, but would welcome any tips. That makes sense - just want to know what I’m doing so I don’t mess it up and have to get my IT pal back into the mix with egg on my face.

@JohnAtl - thanks. I’ve paused Dropbox for the moment in the menu bar, and will do the logout method that @timstringer suggests as well.

Thanks all so much!

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