iMac 27" Late 2013 Slow Downs (Spinning Wheel)


My Late 2013 27" iMac’s performance is starting to become very frustrating (Spinning Wheel).

The specs of the device are as follows:

I5 Processor (3.2 GHz)
Nvidia Geoforce GT755 (1GB) Graphics Card
3TB 7200 RPM Start Up Drive
2TB USB2 GDrive (Photo Storage)
2TB USB2 WD (Time Machine)
OSX Mojave 10.14.6

I run Clean My Mac weekly and the performance increases some but after a few days it seems we are back in the same place performance wise. I also cleared the PRAM.

The frustrating part is that it happens when opening applications, opening web pages, the Finder or just about anything. Logic tells me that there is enough RAM in the machine and a 7200RPM Drive is better than a 5400 RPM Drive but not as good as a SSD performance wise.

At this point I do not want to make the performance worse by upgrading to Catalina by know eventually I will need to.

My thoughts were to do the following steps troubleshooting:

Remove the External Storage (Temporarily) and see if the behavior still occurs. Maybe USB2 attached storage is slowing down the whole system. If so replace it with a USB3 or ThunderBolt (kinda this is not much of an option) - Any recommendations on manufactures?

Reinstall the OSX for the Recovery Partition.

Nuke & Pave and reinstall Mojave

If that does not work buy an External SSD and boot it from the Startup Manager Startup Disk. Any recommendations on manufactures?

Last thing buy a new machine because this one is 6 years old

Any advice would be appreciated.



Can you not get an SSD installed into the machine to replace the 3TB disk?

I swapped out the Spinning disk in my 2014 Mac Mini for a 250GB SSD, it wasn’t very expensive and it was like night and day, went from unusable to fantastically fast.

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I looked at the number of steps (40+) to install a SSD in an iMac and the possibility that I might break the screen as a show stopper. This is why I am looking at an external SSD solution. I ran Black Magics Disk Speed test (Free Download in the APP Store) on the internal SATA drive (7200 RPM) and came up with a write speed of 122.3 MBps and a read speed of 96.7 MBps. Now I have a bench mark to start looking USB3 External SSD to use as the startup disk.

I have eliminated the USB2 external drives a the problem because after running Clean My Mac the spinning wheel happens with no disk storage attached.

I am going to re-install OSX next and see if this makes a difference, I do not believe it will.

Thanks for the response.


Might be worth seeing how much Apple or a service centre would charge to install an SSD.

Cheaper than a new computer.

Unfortunately Apple will decline to install an SSD in a computer that came with a spinning HD.

Locating an Apple Authorized Service Provider (AASP) would yield the best results for a SSD install/upgrade.

My experience is that the spinning HD is showing its age and that would explain its poor performance. A “Nuke and Pave” of the OS would be a good start however. I wonder how the system runs in another User account???

What happens when you use an external SSD as the startup disk? Does that still give you the behaviour described? My experience is that after 5-6 years spinning drives in iMacs tend to be at “end of life”. I had the same issue on a 2012 iMac last year.

If it’s still running: clone it asap, and make backups of everything important!

I’ve solved my issue temporarily by hanging a Samsung T5 SSD off the iMac until I could save enough to buy a 2017 iMac second hand. It got me through last year, and worked great.

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Let me try booting from an external drive to see if I get the same behavior.

I run a 13" MacBook (2009) from an external drive WD My Passport drive (5400 RPM) with no issues. I can clone the drive with Carbon Copy Cloner (that is what I used for the WD My Passport drive)

How was the performance using the Samsung SSD as the start up drive?

What was the interface USB 2.0 or USB 3.0 on the 2012 iMac?

Thanks for the response !!!


booting from the SSD (USB3) made my mac faster than before. I had the choice whether to put in an ssd or get another one. In the end seeing that it could not upgrade to Mojave I decided to buy a new one.

tip: you can always try a thunderbolt ssd, that should be even faster.


Thanks for the advice, I am going to go with a 1TB Samsung T5. Good reviews from most people, I figure I can probably get a another 2-3 years out of the Late 2013 iMac for $150.


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My 2010 iMac had the same issue but I concluded that even if I put an SSD into it, it would still have a bottleneck getting data in and out via USB 2 / Firewire 800. The USB 3 ports on the 2013 make a difference. I have a couple of Samsung T5’s which are great, and the prices have come down a bit over the past year. They are certainly worth getting and will still work with whatever machine you get next. I would also look for an independent Apple repair place like and see if they can fit an internal SSD for your iMac.

Hello All,

Just a little update. I installed the Samsung T5 and migrated all of my data via Time Machine and so far the results are amazing. Black Magics Disk Test went from a write speed of 122 MBps to 400Mbps and the read test went from 97MBps to 405MBps. The system response is like night and day !!!

I will let you know more as I verify my applications, data and backup (Time Machine and BackBlaze).


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nice one!
Hope it makes the machine work for you again.