I'm the proud owner of an 27-inch iMac 2012 with high-end configuration, but the 1TB fusion drive keeps being the bottleneck. As my warranty has expired now, I want to upgrade the 128GB SSD to a larger one (preferably as large as possible), but I want to keep the traditional HDD for storage reasons, and upgrade it later.

Here are my questions:

  • What type is the slot the iMac has for it's SSD? In the iFixit repair manual it kind of looks like an M.2 SSD, but I'm not sure.
  • What is the maximum size (length) for SSDs to fit into that slot? I know that there are different sizes of M.2 SSDs (if it's M.2 at all).

I've heard of adapters that translate that whatever slot the iMac has to a regular SATA connector, so one can use regular SSDs in an iMac. This is interesting because regular SATA SSDs are the cheapest, after all, and offer larger storage options.

  • Does anyone know if these are usable (maybe recommend one)?
  • Would it be possible to place an 2,5" regular SSD (e.g. Samsung 850 Evo) somewhere in the case of the iMac and hook it up to that adapter?

I'd be glad if there's anonye out there to answer some of these questions. Thanks in advance!

EDIT: Allan said in his answer that an mSATA SSD is used in the iMac late 2012. Anyone who can confirm this?

3 Answers 3


I have an iMac 27 Late 2012 and I upgraded my SSD.

The fusion drive is a misnomer - it's actually two drives. There is an PCIe SSD, probably about 128GB that attached to the logic board, then there's a 3.5" 1TB HDD. Technically, you could upgrade the PCIe blade SSD drive, but after some research, I found it wasn't really economical.

All you need is a standard SSD to replace that HDD. You then create a fusion drive using CoreStorage and you will end up with an SSD with 1.13 TB of total storage.

As per Everymac.com....

enter image description here

The basic steps for this upgrade are:

  1. Back up data
  2. Remove the screen
  3. Replace the SSD (you will need a 3.5" to 2.5" HDD adapter
  4. Replace the screen
  5. Reinstall / Restore from Backup.

I've actually answered this question on another thread: 27 imac Late 2012 HDD Failure

While you are doing all these upgrades, I would upgrade the memory as well. I used Crucial Memory and your iMac can get up to 32GB of RAM

  • Thank you for your answer, I am aware that the FusionDrive consist of two individual disks. That's why I said I want to keep the HDD in place and just swap the SSD. I know that just replacing the HDD by an SATA-SSD is much easier, but I plan to upgrade the HDD to like 5TB drive for data and the SSD to like 500GB for software and stuff. The idea of swapping the memory as well is nice, but I'm already at the maximum of 32GB ;) But you said it was an mSATA SSD, that already helps me a lot.
    – LukeLR
    Commented May 26, 2016 at 22:36
  • FYI - 27" iMac doesn't require taking the screen off to upgrade RAM.
    – Hefewe1zen
    Commented May 27, 2016 at 0:19
  • Glad I could help. You will have to remove the logic board to get access to the SSD. What I did was go with an external T'bolt (8GB) for my data and putting in a 1TB SSD where the spinning hard drive was. (I thought about putting a 4TB HDD in there as well)
    – Allan
    Commented May 27, 2016 at 1:15
  • I updated my answer - it's not an mSATA drive as I originally thought - I double checked and remembered it was proprietary PCI which was one of the reasons I decided against upgrading. OWC has a blade SSD, however.
    – Allan
    Commented May 27, 2016 at 2:31

The slot is proprietary, and it is not an M.2 or mSATA slot.

I have seen no adapters on the market that will allow you to connect an ordinary SATA drive to the proprietary connector. Such an adapter would need to include an amount of electronics, as it is a completely different interface - i.e. it is not just a passive adapter.

The only other supplier of compatible SSDs than Apple that I know of is OWC (Macsales). They have a series of SSDs (Aura 6G) compatible with the late 2012 model of the 27" iMac:



I can confirm that swapping the apple SSD for some other SSD is possible in the late 2012 iMac. But I can also confirm that the connector used by the Apple SSD is not mSATA: Although it has the same pin layout, the pins are smaller and don't fit the connector of an mSATA SSD.

Fortunately, I can confirm a third thing: There are adaptors available to convert this proprietary apple connector to a standard mSATA connector. Those are easily found on the Internet on various online shops, and usually called "iMac 2012 mSATA adaptor" or anything similar. I only found one called "MacBook Pro 2012 mSATA adaptor", but that one worked as well, so the connector in 2012 MacBook Pro seems to be the same as the one in my iMac.

Still, use such adaptors with caution! Even if it's really low-tech (narrowing the pin layout a bit, no electronics needed), they may be faulty and might damage to your hardware.

Furthermore, don't forget about the fan issue when swapping the HDD as well: The iMac's internal fan controller won't recognize the HDD temperature of a non-pre installed HDD, even if it's the same brand and model: Apple has built proprietary firmware for the drives shipped with Macs, probably to prevent users from swapping them. I can confirm that this issue applies for the late 2012 iMac as well.

See my photos for pin differences of the original Apple SSD and the mSATA SSD, as well as the installed adaptor.

pin differences of the original Apple SSD and the mSATA SSD pin differences of the original Apple SSD and the mSATA SSD installed adaptor installed adaptor

  • does using the adapter implies loosing speed?
    – andilabs
    Commented Jan 2, 2018 at 8:50
  • 1
    No. First, the SSD is always slower than the bus, if modern busses are to connect the SSD. And second, the adapter is just adapting the size of the connector. Apple is using standard connectors here, but makes them a little bit narrower, so users can’t install regular SSDs.
    – LukeLR
    Commented Jan 2, 2018 at 13:09
  • do you belive the SSD (mSATA (mini PCIE) like this allegro.pl/… will work ok? From where did you purchase the adapter?
    – andilabs
    Commented Jan 2, 2018 at 13:11
  • @andi The SSD will work, It's probably the same as I used (Samsung mSATA 512GB), but not without an adaptor. You'd need to do the same procedure as I did, including using an adaptor. I don't remember where I bought the adaptor from, but I'll have a look, if I can find the source again :)
    – LukeLR
    Commented Jan 10, 2018 at 10:39
  • Sorry, I can't find any information on where I bought the adapter. But I guess, a quick google search with the keywords I provided in the post will give you some resources to get this from :)
    – LukeLR
    Commented Jan 10, 2018 at 10:51

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