iMac late 2014 NVME upgrade

A standard M.2 SSD will not work in a Mac without the use of a third party Sintech adapter. Keep in mind Samsung will not provide any support for you when their NVMe SSD is installed into an iMac (nor will Apple). OWC provides a drop in replacement NVMe SSD which is fully supported by OWC.

https://eshop.macsales.com/shop/ssd/owc/imac-27-inch/2013-2019

Plus you need to make sure the iMac's firmware is up to date so it can communicate with an NVMe SSD. You will only be able to use macOS 10.13+ on this iMac when used with an NVMe SSD.

Hi IMAC1TB,

Welcome to the Apple Support Communities!

We understand that you've obtained an iMac and you'd like to know if the hardware is upgradable. Here's a great resource which covers the features of your iMac that can be upgraded: US iMac (Retina 5K, 27-inch, Late 2014) - Technical Specifications

We hope this helps.

Cheers!

Here is a video that shows the painstaking steps necessary to install a PCIe SSD into a Late 2014 iMac. You have to completely disassemble the iMac and with each step in this process, you risk causing damage that will cost more than you paid for the iMac to repair.

The challenge will be to find an external PCIe drive enclosure now that doesn't require TB3 or USB-C cables and can connect to your USB-3 ports on that iMac. One option that is slower than the Samsung 980, but just plugs into your iMac USB-3 port is the OWC Envoy Pro Electron, which also comes with a USB-A adapter cable. Had you held out for a 2017 iMac, you would have had TB3 ports and other performance options.

[Link Edited by Moderator]