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OWC Tears Down 21.5-inch iMac Retina 4K, Confirms Memory Is Soldered

[Update 04/04/17:] Apple Talks New iMac for ‘This Year’, Hints at Mac mini

Along with the newly released 27-inch iMac with Retina 5K display released by Apple today, we also got our hands on the brand new 21.5-inch iMac with Retina 4K display.

Check out the gallery below to see what we found when tearing down the Late 2015 21.5-inch iMac.

Some noteworthy observations from the teardown:

  • Model name: iMac (same model name as 27”)
  • Model ID: iMac16,2
  • Memory is soldered in. OWC recommends buying as much memory as you can at the time of purchase to increase the longevity and usefulness of your iMac.
  • CPU is soldered in.
  • New keyboard is interesting. A lot of things have changed size-wise. Closer to the MacBook style key, much shorter throw.
  • New mouse feels the same (likely the goal).
  • 4K Retina display looks just as great as the 5K, just smaller.
  • Notably slower startup vs. fusion drive equipped 27” iMac.
  • Two Thunderbolt 2 ports (Check out OWC’s Thunderbolt Central)

[nggallery id=105]

More unboxings/teardowns:
See our teardown and unboxing of the 27-inch iMac with Retina 5K display (Late 2015) here:

OWC has a great selection of portable and desktop drives. And be sure to check out our Thunderbolt Central page for high performance Thunderbolt solutions.

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  • I have a 16,2 iMac with a 1 TB HD (spinning) standard factory & 8 GB RAM. I am not sure why, but it is running very, very, slow. I am trying to figure out why. I’ve always been a Dell/Windows guy where I could easily open the device and make quick upgrades. To my understanding in this blog, I can’t upgrade the RAM due to it being soldered. Could it be the harddrive going bad and how would I know? On my Dell, I would automatically upgrade the HD every 3 years just to be safe. On the iMac files take forever to open even when all other apps are closed. When I look at how much of the processing is being used, I’d say about 4-5 GB of RAM is being used at any given moment. I am near close to restoring the iMac to factory settings to see if that works. If that doesn’t, then perhaps upgrading the hard drive to a SSD. Thoughts from the community because this iMac runs so slow to open files (1-10 minutes sometimes). All we mainly run is Outlook mail, Word, Safari, Powerpoint so we aren’t running any super complex programs.

    • Hi Willian.

      Have you repaired de disk in disk utility?
      Have you tried SMC and PRAM reset?
      Have you noticed in Activity Monitor if is the “kernel process” is the one which is stealing processor power?
      Have you tried to initiate the system in security mode? (Turn on with shift key pressed)
      Have your tried command + D to enter in Apple Diagnostic Tool?

      • Daniel, thanks for the inputs. Negative on all your good inputs. I did a complete restore and it still runs slow. Sometimes taking 30 seconds to 2 minutes now to open up just one program. I ordered a SSD this past weekend and will swap out it with the original spinning HD. I’ll keep your inputs in mind between now and the time I swap it to see if anything improves.

      • Replaced original 5400 RPM factory spinning hard drive with a SSD from Solved my problems. iMac is running again a lightning speeds. I can open program in less than 1 second, and not wait for 1-10 mins. I’ve tested it up to 10 programs opens and they open fast. My iMac is saved! Originally I thought it was perhaps failing RAM.

      • I’ve got the 21 inch late 2015 IMac same problem. Just try installing your system on SSD even if it’s an external one, I boosted my speed maybe 5 times faster..

  • Hi there. I have the late 2015, 21.5 inch with a 5400RPM HDD. 8Gb RAM, my question is it fast and smooth for photo editing with adobe Ps and Lr?

    Im just got yesterday with very less information about this imac.

  • Hi there. I have the basic late 2015, 21.5 inch with a 5400RPM HDD. Can I take that one out and install a 2.5″ SSD? Thank you!

  • i have imac 4k late 2015 with 1TB normal Hard drive 5400 rpm , can i replace it with any 2.5 ssd and get the full speed of the ssd ?

    • Yes! if you imac is a 21.5″ your HD has the same size of a SSD.
      If it’s a 27″ 5k you’ll need an adapter as the HD is a 3.5″.

  • I own a late 2015 4K iMac having intel core i5 clocked at 3.1GHz and a superbly slow 5400rpm 1TB hard drive. So, my question was if I could shell in a 128GB SSD to create a fusion drive ? Is this even possible? Because I read on some site that the late 2015 21.5″ 4K iMac lacks an SSD connector internally!

    • Thank you for your questions and we are sorry for the late response. If your late 2015 4K iMac only came with a HDD when purchased, you will not be able to add a PCIe based SSD as the connection is not there. Please feel free to contact our Technical Support Team for any further questions.

  • I own a late 2015 4K iMac having intel core i5 clocked at 3.1GHz and a superbly slow 5400rpm 1TB hard drive. So, my question was if I could shell in a 128GB SSD to create a fusion drive ? Is this even possible? Because I read on some site that the late 2015 21.5″ 4K iMac lacks an SSD connector internally.

  • Sorry if this question is already answered. I have an Imac 21.5 late 2015, i7 3,3 ghz 16 gb ram and 1tb fusion drive and I want to know if it is possible to upgrade the fusion drive(maybe the HDD part) to a SSD?

    • No need to be sorry Julio! As you have a fusion drive your late 2015 21.5″ iMac 4K you will be able to upgrade the internal HDD to a SSD! If 4K iMac only comes with an SSD, Apple does not include the necessary hardware to add a 2.5″ HDD or SSD. Please contact us if you have any further questions!

  • If we have an 8GB RAM unit, is it possible to get 16GB in it after the fact?

    • Hi, Rich. Unfortunately the memory in the 21.5-inch model is soldered in and can not be upgraded.

      • To expand on the upgrade, aren’t there two available open slots for additional ram? going by the unavailable memory options for this model I’m guess not but I’d like to confirm. Thank you

        • Hi bill!
          The new 21.5″ retina imacs come with soldered ram. The only way to upgrade is asking to at the moment of purchase. Or maybe with soldering skills.

  • If I replace the 1TB HDD with a 1TB SSD will I have the same problem with the fans going full speed as with the 27″?

    • Hello Eduardo,

      If you are replacing the 1TB HDD with a 2.5″ SATA SSD you will not have any fan control problems. Your computer will run as it should!

      If you have any further questions, please feel free to contact our Technical Support Team!

      • Why not? If the sata SSD doesn´t have the thermal sensor built in, the emc will think this is faulty and will run the fun at fully speed. Could you please explain me why I won´t need the adapter in this model? Thanks a lot!

        • Hello Cauac,

          The Apple hardware in the 21.5″ iMac 4K allows any 2.5″ SATA drives temperature to be properly read. There will not be any conflicting issues.

          If you have any further questions, please contact our Technical Support Team!

  • If you go for the 2TB fusion drive, is the SSD still paired with a 5400-RPM drive? How’s the performance of this for digital audio compared to using a 7200 RPM drive (non-fusion)? The same, better, slower?

  • It seems that iMac 4k (with normal hard drive)does not have a PCI-E inteface to install nvme SSD.
    with Fusion Drive version does have a PCI-E interface to load nvme SSD.

  • Shocking: In the purchase process…
    Choose Storage
    Click: How much storage is right for you?
    will show:


    1TB Fusion Drive pairs a 1TB hard drive with 24GB of fast flash


    — enough to store important OS X files and applications to ensure fast startup, near instant wake from sleep and quick application launching, with room left over for your most frequently used files and apps. The 2TB and 3TB Fusion Drives pair a larger hard drive with 128GB of fast flash storage, providing even more space for your most frequently used files. For the best performance, iMac systems with 32GB of memory should be configured with a 2TB or larger Fusion Drive or all flash storage.

  • Can the 21.5″ 4k iMac’s hard drive be replaced/upgraded from the stock 5400rpm hard drive? I was thinking of putting in a 7200rpm hard drive or flash drive on mine. Thanks.

    • I also would like to know that. I have a 500GB Apple SD drive from my 2011 MBP. I’d like to know if it would work in the new iMac 21″ 4k???

      • With the new iMac 4K with Retina you will be able to replace the factory installed drive. You will be able to use any 2.5″ HDD or SSD.

        If you have any further questions, please feel free to contact our Technical Support Team!

  • What is the real-world speed of the new 2015 Apple 21.5-inch iMac SDXC reader? Does it support UHS-II Maximum Speed (300 MB/s read/write)?

    • This is not planned obsolescence.
      This is building an iMac that will last for a decade.

      There are few parts that can go wrong. It will last way beyond the useful life of Windows PCs.

      For example, I’m still using a MacBook Pro 17 from 2006. This is the non-core Duo Model. Sure, it is no longer supported by the latest OS, but it still runs great. It’s CPU is also soldered in. That is 8 years of life and going.

      Macs last so long, I have 11 in use at home. I can have one in every room of the house. I keep 5 working on my desk. Each can be dedicated to running certain tasks – talk about multitasking. Only my PowerPC models have been retired – though they still run well. I keep a shelf full of them. I just don’t have the desk space nor need for more multitasking.

      • So what yoi’re saying is that your older macs, with slotted RAM at least, lasted that long anyway?

        This is Apple blatantly hating on the consumer. Pleeenty of space for a couple of RAM slots in there. They sure haven’t done it to save us money!

      • You’re right. Macs last so long. I’ve had my MBP 15″ since 2005 and it runs well. But after a decade, I need another computer. I am now planning on an iMac 21 retina with 16gb memory and 256gb flash storage.

        My question is, since I keep my computer for so long, will I be able to later increase my flash storage to 512gb or is the area ‘soldered’ as well?

        • Hello Cece,

          Thank you so much for your question. The PCIe SSD will not be soldered in. However, at this time there are no available SSD upgrades.

          If you have any further questions, please contact our Technical Support Team!

          • I’m a little confused. In an earlier reply, you said that any 2.5″ SSD or HDD can be used. I’m also new to all this, but the HDD you pulled from the unit is SATA? I see many 2.5″ SATA SSD’s online – does this mean I can just pull the HDD and replace it with one I purchased?

            • Hello dmp,

              Thank you for your question and sorry for any confusion. At this time you can only add/upgrade a 2.5″ SATA HDD or SSD into the main (SATA) bay.

              If the 4K iMac was purchased with a Fusion Drive or SSD, they will also have a PCIe based connection. However, at this time there are no compatible PCIe SSD upgrades.

              *Please note that if the 4K iMac was only purchased with a HDD, it will not have the PCIe connection.*

              If you have any further questions, please contact our Technical Support Team!

              • hello, I just bought an iMac 16,2 with an SSD 250GB (i7 quad core 3.3ghz) and an MBP 15″ i7 quad core 2.8 ghz 500GB SSD. Since both are PCIe, is the new PCIe SSD 1TB upgrade will be available for the iMac?
                Thanks for your answer

                • Hello Serge Q,

                  Thank you for your question! At this time we do not offer the compatible PCIe SSD for the iMac 16,2. We are always looking to have the most up to date upgrades. Please keep up to date on new product releases by signing up for the OWC Newsletter!