However, if you customised your model and it only has a 'Blade' SSD installed, then you can still install a standard SATA 2.5' hard drive in 21.5-Inch models and a 3.5' hard drive in 27-Inch models.

All 'Tapered Edge' iMac's from the Late 2012 iMac13,1 up to the 'Mid-2017' iMac18,3 models have a 6 Gb/s Serial ATA (Revision 3.0) connector that is occupied by a hard drive in the default configurations.

If you have only have a 'Blade' SSD installed.

You can house your original factory Apple blade SSD in the Envoy Pro enclosure for June 2013 to current Macs.

However, unlike the early 2013 model, even if your system was ordered with only a HDD installed, the PCIe connector for the blade SSD is still present on the motherboard. (The only upgrade path is to install a genuine Apple SSD pulled from another machine).

There are currently no supported aftermarket upgrades for the ‘blade’ SSD in the Late 2013 and onward 21.5-inch iMac models.

If you have a ‘Fusion drive’ setup, then you’ll need to split the fusion drive first and then perform the clone operation.

Your old 2.5-inch HDD can then be housed in the enclosure.

To clone your existing OS/app setup first, purchase a cloning cable or 2.5-inch HDD/SDD enclosure to connect your new HDD/SSD to your mac, then use the Super Duper app to perform the clone, then switch the drives.

Use the iStat widget to check which fan is running fast and check the associated sensor is connected properly. If your fans are running fast after upgrading, you may not have reconnected one of the temperature sensors properly.

No additional thermal cable is needed for all 21.5-inch 2012-onward iMacs.

Follow this guide to perform the upgrade.

To upgrade the factory 2.5-inch HDD, you’ll need the general servicing kit, plus a larger 2.5-inch HDD or 2.5-inch SSD. At the time of purchase, Apple offered a 1 TB 'Fusion Drive' (which combines a 128GB ‘blade’ SSD and a 1 TB hard drive), or a stand-alone 256GB/512GB blade SSD. The iMac late 2015 21.5-inch iMac models have a standard 1TB 2.5-inch factory HDD with a 6 Gb/s SATA port.Sadly, the RAM is soldered to the motherboard in this model, and is not upgradeable.

Clone fusion drive to ssd