iMac 27 5K late 2014 unstable after SSD upgrade

The Crucial MX500 SSD is a good choice and works well with our Macs.

Lets check the health of your SSDs and look for possible software issues by running DriveDx and EtreCheck respectively. Post the reports here using the "Additional Text" icon which looks like a piece of paper. Make sure to post the DriveDx report for both the Apple SSD and the Crucial SSD.

Also run the Apple Diagnostics.

Disconnect all external devices to see if one of those devices is causing the problem.

rk1ssj wrote:

Hi,

I've upgraded a late 2014 27' 5K iMac with an Crucial MX500 1To SSD.

(iMac 15,1 I5 3,5Ghz, 32Go RAM)

The Imac was originally running with an 1To Seagate HDD, fusion drived with a 128Go Apple SSD blade.

The installation was flawless.

But troubles came after the Imac was set up and running.

1st Case - FusionDrive running Big Sur

I create a new fusiondrive container with the freshly installed SSD, installed a Catalina copy and finally updating to Big Sur.

after a couple of hours using the mac, everything starts to slow down and the mac was almost unusable, "color wheel" and the mac take 5 minutes to open a simple folder ...

monitor activity show "kernal_task" using more than 250% CPU

Tested the two disk with driveDX => all OK results

2dn case - Catalina on Apple SSD blade

After issues trying the fusiondrive, decided to split it.

Installed a copy of Catalina on the Apple SSD blade and APFS formatted the Crucial MX500.

at the beginning, it seems OK, but randomly the mac goes black screen and wake up by moving mouse or keyboard (like it goes on sleep) (all energy save option have been disable)

NVRAM have been resteted

have trying to enable TRIM

Was confused, because the OS was running on the original SSD blade and have no clue where the issue are from.

any help would be highly appreciated.

Regards.

William

Not all drives are compatible or best suited for Mac—

You don't need a Fusion Drive when using two SSDs. I recommend breaking the Fusion Drive and only installing macOS to one of the SSDs. You can configure macOS to put the home user folder(s) on the Crucial SSD while you keep the macOS system files on the smaller Apple 128GB SSD. Other more knowledgeable contributors will need to assist you with this endeavor.

How does the system perform when you have a clean install of Catalina? Big Sur is a brand new OS which still may have some kinks to work out compatibility wise.

Make sure to have frequent & regular backups.