Model A1419 / EMC 2806 & EMC 2834/ Late 2014 or Early 2015 or late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 Processor / Retina 5K display

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Upgrading from 2TB Fusion Drive to NVMe/SSD Blade/PCIe SSD/M.2


I am considering buying a used late 2015 iMac. The specs are:

  • 2TB Fusion Drive
  • 24GB RAM
  • AMD M395
  • i5 3.3 GHz

I currently have a MacBook Pro Retina, with SSD blade, and it is fast! I'm afraid that the late 2015 iMac would be slower in terms of read/write speed, since it has a HDD (Hybrid: HDD and SSD).

My Questions are:

  • Is it possible to upgrade the iMac´s Fusion Drive to a for example Samsung 960, or do I need a specific Apple NVMe flash drive for this? And in addition have an SSD to replace the HDD
  • Does the Mac come with the SSD slot?
  • If the iMac is equipped with Fusion Drive, does that mean that the iMac already has the SSD Blade installed? If so, how many GB is it?

One more Question

  • I read the the 1TB Fusion comes with a flash drive, but only 24GB, and the 2TB comes with 128GB.

My question is, is it possible to "Separate" the drives, so that in finder, I can have two volumes.

Update (12/28/2017)

I "accidentally" split the Fusion Drive. And wasn´t even necessary using Terminals. Take a look:

Block Image

I just selected "Fusion Drive" from Disk Utility, then did a 128GB partition. After that, I got two separate disks - separating the HDD and SSD. Erased both drives to APFS.

So I named the SSD "MacOS". Installed the OS to that. Then moved my "Home" directory to HDD.

This configuration now makes sense to me. Got all my programs on the SSD, then movies, documents, pictures etc are "automatically" re-directed to my 2TB HDD.

Don´t think I need to upgrade the hardware.

Answered! View the answer I have this problem too

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The newer iMac's have two drive ports a 3.5" HDD and a custom blade SSD. Depending on the when the model was released it will have a two or four lane PCIe/NVMe custom Apple SSD.

A Fusion Drive'd system leverages both drive ports (each has a device) so there is no free ports.

So moving on what you can alter here... You can break the Fusion drive set to the discreet drives (which you need to do first) How to split up a Fusion Drive. The easier alteration is the swap out the HDD to a 3.5" SSHD or 2.5" SSD drive (with an adapter frame) in either case you'll need this part as well: OWC In-line Digital Thermal Sensor for Hard Drive Upgrade for 27" iMacs 2012 and Later and here is the IFIXIT guide: iMac Intel 27" Retina 5K Display Hard Drive Replacement. Replacing the blade SSD can be done but its a lot more work. Here's the IFIXIT guide to do that: iMac Intel 27" Retina 5K Display Blade SSD Replacement The rub here is getting the correct Apple SSD or go with OWC or Transcend SSD (both are only two Lane PCIe units).

Do be careful taking the display off as its very easy to damage it if you don't use the correct tools and follow the techniques shown in the guides. If you don't it would be a very expensive Oops!

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I´m sorry, but I may be confused... Thanks for the long write up!

I can split up the 2TB Fusion Drive - which means I should have one HDD volume (Which is 2TB 3.5") and one SSD volume (Which is a 128GB(?) SSD blade that is already is pre-installed to the iMac)

Am I correct to say that the iMac DOESN´T have SSHD, but rather a 2TB HDD working with the 128GB SSD Blade?

Am I in the right track here? If so - my question is - I would like to upgrade the blade to for example a 256GB or 512GB and having a separate HDD (Splitting the Fusion Drive)


Correct! You have TWO drives which are logically linked into One 'Fused' drive. It is not a SSHD which is similar! It is a single drive (SATA 2.5" or 3.5") which is a standard HD but has a SSD mounted for a deep cache. You can't see the SSD or alter it. You could put a SSHD into your system (Seagate makes a nice one) replacing your current HD drive.

You are also correct the current drive config (2 TB Fusion Drive) has a small blade SSD.

Before you alter anything you need to break the Fusion drive back to discreet drives otherwise you could have issues repurposing either drive.

As for replacing the blade SSD it's a lot more work to get to. Maybe its best to leave it and just use it for your boot drive and just put in the SSHD to get the speed you want here (hosting some of your apps and all of your data files).


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@danj I'm thinking out loud here. The specs say: This model is equipped by default with a 2 TB "Fusion" Drive, which combines a 128 GB SSD and a 2 TB hard drive. It has a Serial ATA (6 Gb/s) connector for a 2.5" hard drive and a PCIe connector (PCIe 2.0 x4 NVMexpress interface) for the SSD.

Given the size of the existing SSD blade, I do not see how changing out to a SSHD in place of the 2TB standard drive would help. I would think adding a 2.5" SSD drive in a 960GB version and fusing it with the blade would work much better. 960 GB OCZ SSD

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The newer 'Thin Series' 27" models have a 3.5" HDD. It's the 21.5" models that have the 2.5" EveryMac is in error here. I had asked Brock if we could add the details to help people he beat me to it ;-} I'll fire off a note for the correction.

I wouldn't fuse the drives. Besides right now High Sierra still doesn't support APFS with Fusion Drives or RAID.

A dual drive setup with the OS, Apps & Cache on the blade makes sense, then use either an HD or SSHD for the deep storage. If you're doing massive video or music editing you need an external RAID'ed Thunderbolt drive set for the speed and depth.


@danj welcome to the graybeards, glad Addison finally got the problem solved. The only problem I have is the color. I have let mine grow since Thanksgiving and it is totally white.


@mayer - Recheck EveryMac ;-} Fixed!


@danj Thanks for getting Brock to fix this. He does a tremendous job for very little thanks, just like us ;-)


@mayer - He only altered the one ;-{ I hope he'll fix the others.


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Henrik will be eternally grateful.
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