SSD upgrade iMac 21.5 Late 2015 2.8GHz

Just now reading this thread...sorry to dredge it up, but I was curious what route you took? Did you replace the SATA HD w/ SATA SSD or did you augment it w/ PCIe SSD? If the latter, what size/model and did you use AHCI or NVMe? I believe either protocol would work. From what I understand, the Fusion 24GB component is NVMe, but the SSD-only options are AHCI...but I have not found 100% verification of that.

By the way, even if I had bumped up the model of the iMac I would still end up with a useless, stock 5400 rpm that Apple persists on keeping

I agree with you that the stock 5400 rpm drive is abysmal - it is about 30%+ slower than the stock 7200 rpm drive in a 27" iMac. Unfortunately, unless you check the tech specs page, it is not clear what you are getting as the glossy ads tout the possible upgrades to Fusion drive or SSD, but do not mention the ultraslow hard drive.

I sold a Mini after 2 months because I couldn't stand the slowness (that was before I got smart) and upgraded my MBP to an SSD immediately after buying it.

I would recommend using an Thunderbolt equipped enclosure and install a SSD into that and then begin using that approach. How I would recommend doing it is to clone your external HD to the SSD and then change the boot drive to the SSD. This will dramatically improve startup, shutdown and file retrieval times. Thunderbolt is fast, do not use USB 3.0 as the speed will likely disappoint you.

I doubt you will find anyone that has successfully installed a SSD in a Late 2015 21.5" iMac, they were NEVER designed to be upgradeable.

You may also want to consult with OWC (www.macsale.com) and see if they have developed a solution and also to check with iFixit.

Good luck!

You can't install an internal SSD without voiding your AppleCare warranty and any future extended AppleCare warranty.

Any tampering or breaking into the iMac case, by anyone, will void any Apple warranties and any future repairs directly by Apple.

So, you have no choice, but to use an external SSD in an enclosure.

If you had this iMac for 14 days or less, you can return this iMac for a full refund and purchase another one with the specs that meet more of your needs.

Good Luck!

Useless is a strong and very subjective word, if the machine works it's not useless. However for your needs and expectations it's clear the configuration you bought is not ideal.

Consider getting a Fusion drive or a straight internal SSD. There are many benchmarks available that illustrate the speeds comparing a HD to a Fusion and to a SSD.

My guess is you did not do your due diligence when selecting the configuration you got. Perhaps there is a lesson to be learned there?