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A list of successful iMac 27" (2012-2019) SSD upgrades

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The first post of this thread is a WikiPost and can be edited by anyone with the appropiate permissions. Your edits will be public.
Ruadh said:
Here’s a link back to my original post with a rundown of my setup and my upgrade objectives to compare with the outcomes in my penultimate post.

You can see that my scope extended, originally from an essential storage and screen repair only, to (partly through discussion here) taking advantage of upgrade and maintenance opportunities:
  • With people here discussing SATA SSD upgrades, often in the negative (external drive a better option) I remembered that I had a spare 1TB SATA SSD from a dead laptop, so I realised that it would make a good archive drive for my old project files (infrequent access, but making access more convenient would improve their value to me for project bids in particular). It was a case of something that was not justifiable in itself, but which made sense if I had to pull the machine apart anyway. The fun was that I wasn't sure what fittings my all-NVME iMac would have for SATA. It turned out when I opened it up that it had the 3 & 1/2" brackets only, and that I needed to procure a SATA cable and a 2 & 1/2" bracket converter.
  • While my iMac 27” was out of action, I pulled my old late 2009 iMac 21.5” out of storage to use as an extended display. Trying to build or audit large spreadsheets on a laptop was very frustrating. This became a whole separate project as it was not straightforward. In the end I only got this working with the iMac 27” when it was repaired, but it’s increasing my productivity being able to work across three applications at once (Word, Excel, Preview) when converting pdf data files, a common format for public legislative inquiries, to Excel. The extra screen real estate gives large scale zoomed sheets and pages side by side, perfect for auditing data conversions and a whole range of other tasks, I'm sure. It also gives me access to another 1TB drive for archives (OWC Mercury Electra 3G 960GB SATA SSD) @ 107MB/s read and 80MB/s write to the iMac 27" (first screenshot), the speed reduced by the need to use a GBE wired network, as there is only a Firewire 800 cable option with the older iMac. Yes, the iMac 21.5" can get closer to spec 250 MB/s read and 214 MB/s write internally via the SATA cable only (second screenshot), but I don't expect to be using it that way. That's not storage that I wanted, but I may as well make use of it.
  • Discussion here prompted me to make the most of having the iMac opened up to undertake a whole range of maintenance jobs, including a full clean, thermal paste replacement & PRAM battery replacement (21.5" guide as I could not find one for 27"). The first was essential, the second became a pain when I stuffed up the reassembly, and the third proved impossible when the battery turned out to be non-specification and unavailable.
Thanks all for your assistance.
Click to expand...
Pardon my late response Ruadh,
Well it has been a marathon but you won out in the end. Congratulations! Upgrades are not for the fainthearted as the whole process can become a huge time consuming challenge. It is rewarding to see others succeed. We each learn too from the pitfalls. Thank you for the detailed feedback.
Best Wishes,
 
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@Ruadh — what a journey! Really impressive how you turned a straightforward repair into a full-blown upgrade and optimization project. It’s great that you were able to repurpose that 1TB SATA SSD—sometimes the best upgrades are the ones that piggyback off other work, especially when they add long-term value like better file access for bidding and archival work. The part about using your 2009 iMac as a secondary display really resonated with me; I’ve tried similar workarounds in the past, and I know how tricky they can be. Your productivity gains from the extra screen space sound well worth the effort though.


Also, hats off to you for tackling thermal paste and general maintenance while you were in there—those jobs are fiddly enough on their own, and even more so with Apple hardware!


@Second poster — I completely agree, not for the fainthearted indeed. It’s great to see the forum community helping push projects like this forward, even when they take unexpected turns. There’s a lot to be said for shared learning—successes and missteps included.


Thanks to both of you for the insights. Definitely taking notes for my own upcoming iMac cleanup and storage refresh. Might take a look on PCInternational as well for any good SATA accessories or display solutions.
 
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Hi all. Know this is an old thread, but here in summer 2025, I’m still trying to upgrade my late 2015 iMac. Post Amazon prime day deals (and pre tariffs), I figured now is my last chance to get a cheap upgrade.

I purchased a SinTech adapter and a Samsung 990 Evo Plus and after doing everything so carefully (wearing nitrile gloves, grounding strap etc), I swapped the old nvme ssd blade for my iMac with Fusion Drive and now the computer won’t power on at all. No lights, just completely dead.

The only thing I did extra was replace the PRAM CR2032 battery while I was there (which I had a hard time taking out, and may have accidentally popped out one side of the battery clip off the board although I was able to push it back before I realized there was a spring mechanism on the opposite side to remove the battery… hopefully I didn’t break the mainboard?!).

In any case, I suspect incompatibility between the Sintech and the very new 990 Evo Plus? I haven’t checked the firmware via Samsung magician yet because I don’t have a recent PC with an nvme slot nor external enclosure. It is July 2025 after all so I assume they’ll all come shipped with the latest firmware?

Please, any thoughts on what may have happened here? Thanks all in advance!
 
HappyBABA said:
Hi all. Know this is an old thread, but here in summer 2025, I’m still trying to upgrade my late 2015 iMac. Post Amazon prime day deals (and pre tariffs), I figured now is my last chance to get a cheap upgrade.

I purchased a SinTech adapter and a Samsung 990 Evo Plus and after doing everything so carefully (wearing nitrile gloves, grounding strap etc), I swapped the old nvme ssd blade for my iMac with Fusion Drive and now the computer won’t power on at all. No lights, just completely dead.

The only thing I did extra was replace the PRAM CR2032 battery while I was there (which I had a hard time taking out, and may have accidentally popped out one side of the battery clip off the board although I was able to push it back before I realized there was a spring mechanism on the opposite side to remove the battery… hopefully I didn’t break the mainboard?!).

In any case, I suspect incompatibility between the Sintech and the very new 990 Evo Plus? I haven’t checked the firmware via Samsung magician yet because I don’t have a recent PC with an nvme slot nor external enclosure. It is July 2025 after all so I assume they’ll all come shipped with the latest firmware?

Please, any thoughts on what may have happened here? Thanks all in advance!
Click to expand...
So I put back the old Apple nvme drive and no issues so motherboard and all are good. I contacted SinTech and they don’t think there should be an issue with the 990 but I ordered the shorter version of the same SinTech adapter anyway and the same issue. No power to the board at all. No lights. Nada.

Looks like the 990 EVO Plus just isn’t backwards compatible or supported? Too bad as the slower 970 EVO /Plus/PRO series nvme drives now cost even more than the newer faster 990s. Oh well no dice…
 
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Zrktty said:
Blade + RAM Upgrade - Success ✅
Just updated my friend's iMac, with 0 issues 👌 Here are the results.
  • iMac Model: iMac 27” Late 2013 (iMac14,2)
  • NVMe SSD Installed: Kingston NV3 NVMe PCIe 4.0 Internal SSD 1TB M.2 2280-SNV3S/1000G
  • Adapter: M.2 NVMe to Apple proprietary blade SSD adapter (bought from Aliexpress for 2.30 eur)
  • macOS Version: macOS Catalina 10.15.7 (first reinstalled from HDD Mojave then upgraded online)
  • TRIM Support: Enabled
  • Blackmagic Disk Speed Test Results:
    • Write: 748.1 MB/s
    • Read: 663.7 MB/s
  • Notes:
    • TRIM is active automatically.
    • No kernel panics or sleep/wake issues observed so far.
    • Old HDD kept inside for additional storage, fully accessible.
  • Highly recommend to get the aftermarket adhesive strip kit with the pizza slicer tool included. That was the hardest part.
  • The screw for the nvme card to hold in place on the motherboard is not included, you have to get it from somewhere
Click to expand...
I was going to order that drive, but those speeds seem very low ? Is that a very long test ?
 
HappyBABA said:
So I put back the old Apple nvme drive and no issues so motherboard and all are good. I contacted SinTech and they don’t think there should be an issue with the 990 but I ordered the shorter version of the same SinTech adapter anyway and the same issue. No power to the board at all. No lights. Nada.

Looks like the 990 EVO Plus just isn’t backwards compatible or supported? Too bad as the slower 970 EVO /Plus/PRO series nvme drives now cost even more than the newer faster 990s. Oh well no dice…
Click to expand...

Sorry to learn of your ordeal happyBABA. It appears you purchased your gear before browsing previous comments on this blog. You purchased an incompatible NVME and the wrong adapter for the brand that matters.

Many have warned against Samsung NVME as incompatible with Mac. Some models work but over time slow the Mac down due to trim issues. WD Black NVME SN 850x and WD Black SN770 are recognised as the safest compatible NVME designed for Mac compatibility. My SN770 is working fine for over 3 years.

Samsung is not designed for Mac.

I can say the Samsung 970 Evo SATA SSD works fine on Mac.

See if your dealer will swap the Samsung 990 Evo NVME for a WD Black SN850x or SN770. Alternatively sell the Samsung 990 to fund a WD Black. The SN850x will be very expensive. The SN770 is a better choice as it is cheaper and runs cooler. Use the short adapter as airflow around the NVME will improve cooling efficiency. Both will run at around 2700GB/ps or more on your iMac

That said, your Mac should not be dead after the NVME is fitted. Battery is not the cause. You should see three pilot lights on the motherboard. Absolute minimum one pilot light. Maybe you power plug was not fully engaged in the socket? Maybe you did not notice where the pilot lights are located?

I suggest you go back to P59 and read forward through the discussions. You may recognise why your experience was unsuccessful.

You may then post a question with detailed information on your procedure.
 
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Thanks so much for your very detailed response @Terraaustralis! I also purchased the short adapter and returned the EVO and bought anything else that was cheap and on the SinTech known compatibility list, namely the OCZ RD400 (Toshiba RVD400). I’ll update this thread after it arrives, hopefully with good news. Thank you!
 
Purchased an OCZ RD400 (Toshiba RVD400) and confirm that everything booted up and worked as expected. Turns out the Samsung EVO 990 Plus is absolutely not compatible in its current firmware level with an adapter for the late-2015 Intel iMacs. When plugged into the sintech adapter, even the motherboard lights don’t turn on. All good now with something on the actual compatibility list from SinTech. Thanks all for your help!
 
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HappyBABA said:
Purchased an OCZ RD400 (Toshiba RVD400) and confirm that everything booted up and worked as expected. Turns out the Samsung EVO 990 Plus is absolutely not compatible in its current firmware level with an adapter for the late-2015 Intel iMacs. When plugged into the sintech adapter, even the motherboard lights don’t turn on. All good now with something on the actual compatibility list from SinTech. Thanks all for your help!
Click to expand...
Sounds promising! Tell us your NVME capacity and speed performance with AmorphusDiskMark when the job is done.
 
Received today a second iMac 27" 2015 with a 3TB fusion drive that I got for really cheap, since it got extremely slow and the user was pissed-off and bought an apple Silicon iMac.

As I received it, I booted an USB-SSD with Windows11 to go.
From there I formatted the HD to 2TB NTFS, the rest to exFAT.
Formatted the 121GB blade to NTFS and installed Win11 (Rufus install)
I have a collection of BootCamp drivers on an USB stick which I then installed
Bought a license key for less than 5€ on eBay and activated it. My new Windows is operative (that took 40 minutes).
Then I copied the user folder to the HD and moved my user to that destination
(now my user data expands to the HD and the small blade keeps sleek. With quite a lot of installed applications it is just filled to 50% and will not grow any further)

The iMac needs about 10 sec to show Apple's logo (apparently the SMC still seeks for a fusion drive), but then boots really fast and is blazing fast and it will remain fast !

Optionally I have also a Sonoma installation on an external SSD that boots well and fast too, from there, I installed OCLP on the EFI of the blade and now I get the choice of Windows / Sonoma upon booting.

No need to open anything, nothing to replace, no extra hardware required.
 
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1) HDD upgrade

Device: 2017 27" 5K(3.8Ghz, Fusion drive 2tb)
HDD upgrade: 2 TB SATA HDD -> 500gb Samsung 870 Evo SATA SSD( HDD was dying)
Speed test: around 540 MB/s read and 540 MB/s write on the SATA SSD, 2277MB/s read and 773MB/s write on the NVME
OS: OSX Ventura on the original 128gb NVME, Ubuntu on the 500gb SATA SSD
Location: Norway, Europe
Temperature sensor: none
Issues after fresh OS install: No problems at all, both OS works great on this awesome machine :)
 
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