SSD drive for older iMac

Hello!

The LaCie Mobile SSD Secure USB-C Drive - Apple with a USB-C to USB-A 3.1 adapter cable, such as this one, will be compatible with your iMac (27-inch, Late 2012).

For setup instructions and more info, see:

Use an external SSD as your startup disk … - Apple Community.

Jack

rkaufmann87 wrote:

OWC Mercury On The Go Pro & a OWC On the Pro Go Power Adapter

Hi,

Unfortunately, that particular OWC external drive is one of the few that isn't compatible as a bootable external SSD. The Mercury On-The-Go Pro just works for Mac computers that are 2013 and newer, not before. This is because the chipset used, the ASMedia 1051e, has a compatibility issue with pre-2013 iMac computers, so it may not work on the OP's iMac (27-inch, Late 2012).

Jack

most of the new drives are made with USBC and USB-1 or USB-2 second generation. Late 2012 iMac is USB 3.0

so don’t know if the newer drives would be backward compatibility.

working with Sandisk customer support to see if their Extreme or the Extreme Pro V2 are compatible with USB3.0 and OS Mojave.

The LaCie with the adapter cable is compatible. Also, I'd advise against SanDisk SSDs.

OWC Mercury On The Go Pro & a OWC On the Pro Go Power Adapter