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

[ProteoMX]

Might it be that the 660P is the cure?

Maybe not... I'm using a Samsung 970 Pro and sleep/resume is working flawless so far.

It's certainly not the fastest drive (made slower by the 2013 it's gone into...)

I've run the speed test with Blackmagic's software and my read/write results are around 780/738 MB/s, so your numbers are mostly at the top. The real bottleneck is the bus speed in the 2013 models. I understood that before buying the drive, but wanted the endurance features the Pro series offer.

Notice it's not shown as an internal drive as all NVMe drives appear to be external

Interestingly, in my case the NVMe drive is recognized as internal in System profiler, Finder and Disk utility (which reports it as "PCI-Express Internal Physical Disk". Where can I find the MRI software in your screenshots BTW?





One thing I forgot to mention in my previous post, which may be useful for those trying this. It is possible to buy the real, original adhesive strips used by Apple from eBay. I bought these and they're the real thing (previously I used the ones sold by OWC and they're fine, but a real PITA when you have to remove them). The funny thing is that the original ones are cheaper!

 

[MacManSuite]

Maybe not... I'm using a Samsung 970 Pro and sleep/resume is working flawless so far.



I've run the speed test with Blackmagic's software and my read/write results are around 780/738 MB/s, so your numbers are mostly at the top. The real bottleneck is the bus speed in the 2013 models. I understood that before buying the drive, but wanted the endurance features the Pro series offer.



Interestingly, in my case the NVMe drive is recognized as internal in System profiler, Finder and Disk utility (which reports it as "PCI-Express Internal Physical Disk". Where can I find the MRI software in your screenshots BTW?

View attachment 837722

View attachment 837723

One thing I forgot to mention in my previous post, which may be useful for those trying this. It is possible to buy the real, original adhesive strips used by Apple from eBay. I bought these and they're the real thing (previously I used the ones sold by OWC and they're fine, but a real PITA when you have to remove them). The funny thing is that the original ones are cheaper!

Interesting - I don't know enough about the software side of things.

Speed was expected, this was an upgrade for a client so not bad.

If you hold ALT on boot, you'll see it'll display as an external drive.

MRI - You cannot get.

 

[dobrink]

Since no one I know has had that problem with one in a late 2015, I'm not surprised...

2014 and earlier require a Terminal command...

How comes everyone has been having problems even with late 2015 iMacs, regardless if the iMac was originally HDD-only, fusion or ssd model? It is only those guys later in this post who have just reported issueless upgrade. Can you please share some data to add and compare with the already collected information?

my boot Rom and EFI have updated 10.14.5 , I wonder if this is making a difference ?

Nothing changed here, still have the wake problems in a 2015 5k iMac, originally HDD only. Location Finland.

Late 2014 27" 5K i7 4790k 295x Mojave 10.14.5 ( also worked on an earlier version of Mojave that used HFS+)
Just replaced the Seagate 3tb with a 2TB ssd, and also replaced the 128GB Pcie blade with a intel 1TB + adapter.

Flawless. Goes to sleep, wakes up no terminal command.

Where are you from? Did you try putting the iMac to sleep on a clean install, before you restored the Time machine backup? I.e. could it be so that somehow the sleep-state capabilities transfer from the backup on the external SSD to the new NVMe blade? Will you hold ALT on boot to see if the blade will display as an external drive?

Could you please fill the following:

Blade+HDD upgrade by mdelrossi

Device: Late 2014 - 15.1 - (4.0Ghz i7-4790K)
Blade upgrade: 128GB Blade -> Intel 1TB 660P
HDD upgrade: -> 2TB SSD
Speed test:
OS: Mojave 10.14.5
Location:
Adapter:
Issues after fresh OS install: Flawless. Goes to sleep, wakes up no terminal command.

Hi everybody. I followed the recommendations of this thread to upgrade my Late 2013 iMac 27" to a Samsung 970 Pro M2 SSD with the Sintech adapter. Everything worked without a hitch since the first time! Just one doubt though.

I expected to be unable to put the machine to sleep without a kernel panic, but sleeps seems to be working just fine. I mean, I can hit the "Sleep" menu entry, leave the machine alone for a while and when I press the keyboard it just comes back to life and keeps working as usual.

I do not know of any case where a Late 2013 model would work with a NVMe without sleep issues, mikehalloran says above, they need a terminal command to disable normal sleep. Could you fill the report, such as the above? Also did you restore a backup from a Time machine, or tested the sleep right after a clean OS X installation? Can you hold ALT on boot to see if the blade will display as an external drive?

Another device for you for your list. Upgraded for client due to failing 3TB drive...

Working with NO tweaks to sleep mode, no crashes when resuming. Tested under both 10.14.4 and 10.14.5 with no issue.

Might it be that the 660P is the cure? It's certainly not the fastest drive (made slower by the 2013 it's gone into...)

Another Late 2013 iMac without sleep issues Did you restore a backup, or did you test the sleep right after a clean OS X installation? Where are you from? Can it be area-specific, i.e. firmware upgrades to be geo-locked, due to different policies in different regions? Therefore, I have also added location to the upgrade reports.

 

[mdelrossi]

Blade+HDD upgrade by mdelrossi

Device: Late 2014 - 15.1 - MK462LL/A (4.0Ghz i7-4790K)
Blade upgrade: 128GB Blade -> Intel 1TB 660P
HDD upgrade: -> 2TB SSD-> Sandisk SDSSDH3-2T00-G25

Speed test:
OS: Mojave 10.14.5
Location:us
Adapter: sintech with heat sink
Issues after fresh OS install: Flawless. Goes to sleep, wakes up no terminal command. Clean install, then migrated from existing T5 that I was using as main boot drive.

 

[ProteoMX]

Blade upgrade by ProteoMX

Device: iMac Late 2013 - 14.2 - ME089LL/A (3.4Ghz i5-4670)
Blade upgrade: None -> Samsung 970 PRO 512GB - NVMe PCIe M.2 2280 SSD (MZ-V7P512BW)
Adapter: Sintech NGFF M.2 nVME SSD (came in black color, branded as RoHS)
Speed test: 780 MB/s read, 738 MB/s write.
OS: Mojave 10.14.5
Location: Venezuela
Issues after fresh OS install: Flawless. Goes to sleep, wakes up no terminal command.

I did a clean install of Mojave 10.14 using a USB drive. I did NOT test sleep at this stage. Then I upgraded to 10.14.4, tested sleep and it worked. Moved my data back using Migration assistant (checked everything I think) and after that I tested sleep again and it worked. One day later I upgraded to 10.14.5, sleep still works flawless.

Tried holding ALT on boot and MacManSuite was right, the NVMe drive is detected as external by the bootloader.

 

[mikehalloran]

How comes everyone has been having problems even with late 2015 iMacs, regardless if the iMac was originally HDD-only, fusion or ssd model? It is only those guys later in this post who have just reported issueless upgrade. Can you please share some data to add and compare with the already collected information?


Nothing changed here, still have the wake problems in a 2015 5k iMac, originally HDD only. Location Finland.



Where are you from? Did you try putting the iMac to sleep on a clean install, before you restored the Time machine backup? I.e. could it be so that somehow the sleep-state capabilities transfer from the backup on the external SSD to the new NVMe blade? Will you hold ALT on boot to see if the blade will display as an external drive?

Could you please fill the following:

Blade+HDD upgrade by mdelrossi

Device: Late 2014 - 15.1 - (4.0Ghz i7-4790K)
Blade upgrade: 128GB Blade -> Intel 1TB 660P
HDD upgrade: -> 2TB SSD
Speed test:
OS: Mojave 10.14.5
Location:
Adapter:
Issues after fresh OS install: Flawless. Goes to sleep, wakes up no terminal command.



I do not know of any case where a Late 2013 model would work with a NVMe without sleep issues, mikehalloran says above, they need a terminal command to disable normal sleep. Could you fill the report, such as the above? Also did you restore a backup from a Time machine, or tested the sleep right after a clean OS X installation? Can you hold ALT on boot to see if the blade will display as an external drive?



Another Late 2013 iMac without sleep issues Did you restore a backup, or did you test the sleep right after a clean OS X installation? Where are you from? Can it be area-specific, i.e. firmware upgrades to be geo-locked, due to different policies in different regions? Therefore, I have also added location to the upgrade reports.

You have been crying about this on a number of threads for quite awhile. I’ve never seen enough of what you did to know what you did wrong. Did you mistake an early or mid 2015 for a late model?

Done right, installing an NVMe 3 x4 blade into a late 2015 iMac will not have a wake from sleep issue. The brand of the blade will not matter nor the pin-out adapter. Some blades are a lot faster than others—this is where the brand and model do matter.

If a 2013 to mid-2015, this is not correct but there are a number of Terminal commands that can be used to fix this. A 3 x4 blade is a waste of money in these since these have a PCIe 2 bus but they will work—it doesn’t matter how fast the blade since the bottleneck is PCIe 2. The NVMe 2 blades do not have this issue nor do they require High Sierra.

 

[dobrink]

That's what we are trying to figure out. What Jeden87, ssdaytona, macguru8, MBehr2, MacManSuite, I and others, all with Late 2015 5K iMacs, are doing wrong? Or more exactly, what the few people who have succeeded are doing right... Possible causes investigated in the past were adapter and ssd model, bootrom versions, board-ids, drive type fusion/hdd-only...
Actually, until recently, I did not know of any successful iMac upgrade which wouldn't have the issue on a pre-2017 iMac. Now, obviously, new information is coming in even with iMacs Late 2013 and Late 2014 getting no sleep issues (summary of all the gathered upgrade info here in the 1st post of the thread).

The Intel 660p is working for MacManSuite in a Late 2013 iMac, while Sabrent Rocket is not working in his Late 2015 iMac. ProteoMX has a Samsung 970 Pro issueless in a Late 2013 iMac, while three other reports of 2013 and 2015 iMac read problems with the Samsung 970 Pro. Thus the solution is unlikely to be in the drive.

What spikes interest is this "showing as external drive" upon holding Alt during boot to list all the boot-capable drives. If mdelrossi can confirm that his Late 2014's newly installed Intel 660p shows as external just like MacManSuite's and ProteoMX's then this must be it. Somehow the iMac detects the blade as an external device and thus does not try to put it in the problematic L1.2 PCIe state of the NVMe SSD, from which the system crashes because it cannot wake the drive.

Then it will be a matter of figuring out how to on a software level transition from an internal blade to external one, which would solve the sleep issues because the drive would never enter the lower power state, but instead be on at all times during a non-hibernation sleep.

Meanwhile, mikehalloran, will you be so kind and tell us what iMacs you upgraded, with what NVMes, approximate OS X version etc.

 

[mdelrossi]

I’ll check when I get back tomorrow

 

[MacManSuite]

Both my upgrades were for client machines, as listed in the spec breakdown I gave.

2TB in Late 2015 was a clone from internal drive
2TB in Late 2013 was a restore from TM backup.

Late 2015 would crash upon resuming from sleep, Late 2013 didn't throw any issues.

No 3rd party software running on either that would disrupt sleep/hibernation.

I'll be doing more going forward for clients now NMVe drives have reduced in price and I have two 2015's coming into stock for ourselves that I might upgrade, so will post progress from those.

Edited to add: The Late 2015 was showing as an external drive, not just the Late 2013.
UK Based.

 

[macgeek01]

You have been crying about this on a number of threads for quite awhile. I’ve never seen enough of what you did to know what you did wrong. Did you mistake an early or mid 2015 for a late model?

Done right, installing an NVMe 3 x4 blade into a late 2015 iMac will not have a wake from sleep issue. The brand of the blade will not matter nor the pin-out adapter. Some blades are a lot faster than others—this is where the brand and model do matter.

If a 2013 to mid-2015, this is not correct but there are a number of Terminal commands that can be used to fix this. A 3 x4 blade is a waste of money in these since these have a PCIe 2 bus but they will work—it doesn’t matter how fast the blade since the bottleneck is PCIe 2. The NVMe 2 blades do not have this issue nor do they require High Sierra.

You’re definitely incorrect on this. I have a Late 2015 27” iMac with with a 2TB Sabrent Rocket installed that is unable to sleep without restarting. Apple OEM MVME work fine. This occurs with the latest version of the Sintech Adapter both long and short versions. I know everything is installed correctly and everything else works perfect.

 

[macmanss]

I can confirm the new 2019 iMac 27” works with a 2TB Samsung 970 EVO NVMe and 1TB Samsung 840 EVO SATA SSD.

To add to the compatible list:
Device: Early 2019 iMac 27” - 19,1 (base model 6-Core 3.0GHz i5 with 1TB Fusion Drive)
Blade upgrade: 32GB Blade -> 2TB Samsung 970 EVO NVMe SSD
HDD upgrade: 1TB SATA HDD -> 1TB Samsung 840 EVO SATA SSD (old model)
Speed test: 2900 MB/s read, 2520 MB/s write
OS: Mojave 10.14.5
Adapter: Sintech ST-NGFF2013-C
Location: Sydney, Australia
Temperature sensor: none
Issues after fresh OS install: none, sleep/wake works fine, no loud fans


Here’s some details of my experiences in case someone else wants to do this:

Parts I used / installed:
2TB Samsung 970 EVO NVMe SSD
1TB Samsung 840 EVO SATA SSD (old model)
Sintech ST-NGFF2013-C long black adapter
EK-M.2 NVMe Heatsink - black
2.5” to 3.5” Metal Bracket
Replacement Adhesive Strips
2x 8GB Crucial 2666MHz SODIMM Memory

Notes:
- The iMac came preinstalled with 10.14.4, Boot ROM version 220.250.368.0.0, SMC version 2.46f12. Before pulling apart I upgraded to 10.14.5 using the combo installer and the Boot ROM version increased to 220.260.170.0.0, SMC remained the same at 2.46f12. Blackmagic reported speeds of 1450MB/s read and 880MB/s write with the Apple blade.

- Removing the screen adhesive was a lot harder than previous models, the bond is much stronger, it took about twice as long to get the screen off... probably because I was being extra cautious.

- I used genuine Apple adhesive strips meant for the 2012-2013 models (I already had them). They fit ok but I did cut them a little to fit perfectly.

- Screws and cable positions were mostly the same as the iFixit guide for 2014-2015 iMacs, but there were a few small differences. You shouldn’t have any troubles finding them.

- I attached a heatsink to the Samsung 970 as I read they get quite hot. The front clip went on easy, the rear clip required a bit of bending with pliers to make it fit as the 970 is a little thicker towards the back. I’ve been monitoring the temperature and so far it hasn’t passed 50 deg C under heavy load, mostly 46-48 deg. Currently idling at 37 deg.

- The Apple screw that holds the blade to the logic board wasn’t long enough to handle the Sintech + Samsung blade, nor was the screw that came with the Sintech adapter, probably because I added a heatsink. Had to rummage through my spare screws to find a longer one. This is very important as without a proper length screw the blade may flick up.

- There is a very thin black cable that comes from the chin of the iMac and attaches to the logic board, approx 2-3 inches to the right of the Apple logo when viewed upright. Be sure to detach and reattach when putting back together. I don’t know what it does but it’s easy to miss.

- I installed my old 1TB SATA SSD using a cheap 2.5” to 3.5” metal bracket. I drilled the side screw holes to make them a little bigger. You don’t have to do this but the Apple screws fit better this way.

- I formatted the 970 drive as APFS (Encrypted)... essentially this is FileVault, so if you format as APFS (what most people would use) your speeds may be slightly higher than mine. In theory I could've created a fusion drive, but I chose to keep them separate as a fusion drive doubles your chances of total data loss in the event of drive failure.

- Installing the memory was a little tricky. You need to push them in quite firmly, and when you put the carriage back in, push the memory in firmly once more. Moving the carriage out again sometimes makes the modules come loose.

- The 970 shows as a grey hard drive icon when holding down Option at startup, so it sees it as an internal drive.

- TRIM is enabled by default for the 970 (NVMe) but not enabled for the 840 (SATA SSD).


Just wanted to say a big thank you to all contributors, the information here has been invaluable. I hope this post helps someone else.

 

[ProteoMX]

Very comprehensive post macmanss, thanks. I regret not buying a heatsink, I didn't think it was necessary but I've read some stories about Samsung drives reaching 90º so it would have been a good idea and it wouldn't hurt anyway. I actually bought two Sintech adapters, both the short and long versions, but decided to use the short one precisely because I thought it would allow a bit of airflow between the drive and the motherboard. So far my temps are a bit warmer than yours, it idles at 45º and reaches 52º under "regular" use (web browsing, Illustrator, etc.) but still fairly moderated, so no worries at the moment.

 

[iaanda]

Hi everyone just wonder for who upgraded to both ssd drives (SATA and nvme on the mainboard), are you use diskutil to make them as a Fusion Drive or just leave it as two separates drive?
Check out this

from 2:30,
My question is, Any benefit for merge as a Fusion Drive or just can't be bother leave it one as boot drive and another one as storage?
Sorry for my terrible gramma.

Thank you for sharing in advance

 

[mdelrossi]

I'd just leave it as 2 separate drives.

 

[macmanss]

Very comprehensive post macmanss, thanks. I regret not buying a heatsink, I didn't think it was necessary but I've read some stories about Samsung drives reaching 90º so it would have been a good idea and it wouldn't hurt anyway. I actually bought two Sintech adapters, both the short and long versions, but decided to use the short one precisely because I thought it would allow a bit of airflow between the drive and the motherboard. So far my temps are a bit warmer than yours, it idles at 45º and reaches 52º under "regular" use (web browsing, Illustrator, etc.) but still fairly moderated, so no worries at the moment.

Yeah I considered using the short Sintech for better airflow, but in the end decided to use the long one because if it's going to cook a board I'd rather it cook the Sintech instead of the logic board. Either option could be correct.
[doublepost=1558404653][/doublepost]

Hi everyone just wonder for who upgraded to both ssd drives (SATA and nvme on the mainboard), are you use diskutil to make them as a Fusion Drive or just leave it as two separates drive?
Check out this

from 2:30,
My question is, Any benefit for merge as a Fusion Drive or just can't be bother leave it one as boot drive and another one as storage?
Sorry for my terrible gramma.

Thank you for sharing in advance

Personally I left mine as separate drives. With a fusion drive, if one drive fails you lose the contents of both drives

 

[rbart]

I have a 1Tb Fusion drive 5K (late 2015).
I have read a lot of advices but I have not a clear view about the thermal sensor to add if I replace the 1Tb HDD with a 1Tb SATA SSD.
Some people say it's absolutely required
Other say it's useless.
I don't want to buy a useless thing (around 50€ !!!) and I don't want to have problems or use a soft fan control.

 

[macmanss]

I have a 1Tb Fusion drive 5K (late 2015).
I have read a lot of advices but I have not a clear view about the thermal sensor to add if I replace the 1Tb HDD with a 1Tb SATA SSD.
Some people say it's absolutely required
Other say it's useless.
I don't want to buy a useless thing (around 50€ !!!) and I don't want to have problems or use a soft fan control.

I have upgraded all slim iMac models from 2012 to 2015 with SATA SSD's and have never installed a temperature sensor. None have had fan issues, nor required any fan control software.

 

[rbart]

OK, thanks.
Maybe the best is to test during some days without temperature sensor before sealing the iMac.
Nowadays the temperature sensor cost is high compared to the SSD cost

 

[mbosse]

A couple of comments here:

Yes. The only exception I know are the SSD only iMacs where there is no HDD in the SATA III slot.

There are a number of reports which indicate that several SSDs, particularly Samsung ones, work well even without a temperature sensor or a software solution.

Anyway, you can get away with shorting out the original sensor or substituting a system pull optical drive sensor ($3–$10 on eBay) on the late 2009–2010 only (I don't recommend it but you certainly can). The 2011 requires the OWC temp sensor.

Using the optical drive sensor works very well and is certainly to be recommended over shorting the sensor cable.

The 970 will throttle if they get too hot — on purpose. In a 6.1 Mac Pro it's an issue which is why you should get a heat sink. There's no room for a heat sink in the 2013–17 iMacs—it would surprise me if there is in the 2019.

There is ample space for a heatsink at least in the 27" iMacs. I installed them myself (here a 2015 iMac, using the short adapter):

Do not remove the stickers! They act as a heat spreader by design. Nearly all heat sink makers will include language that they work with the stickers. Besides, you'll void your warranty if do. But that's ok, you probably don't have room.

Sure for the warranty issue - this will almost certainly ruin your warranty. But not all stickers are equal: some are simple stickers without any heat dispersal function (e.g. Intel 760p), some have copper internals (e.g. Samsung 970 Evo) which indeed conduct heat away from source.

Hope this helps those who are curious about the modifications.
Magnus

P.S.: Post edited to replace 'shortening' with 'shorting' to make sense after all...

 

[macmanss]

OK, thanks.
Maybe the best is to test during some days without temperature sensor before sealing the iMac.
Nowadays the temperature sensor cost is high compared to the SSD cost

Yeah you can do that. If the fans haven't ramped up once you finish booting up off the SSD then you're definitely fine. If it's going to happen, it'll happen immediately. Mbosse makes a good point in the previous comment, I have always used Samsung 840/850/860 Evo SATA SSDs. So I can't speak for other brands... maybe that's why some have reported fan problems, yet I've never had an issue, and I've done dozens.

 

[rbart]

My plan was to buy a 860evo or a Crucial MX500

 

[macmanss]

My plan was to buy a 860evo or a Crucial MX500

I couldn't tell you about the Crucial, but in 5 years I've done probably over 50 upgrades using Samsung EVO's, and I'm yet to have one fail *knock on wood*. Also if you happen to live in Australia, Samsung has a cashback offer at the moment.

 

[Woodlandjustin]

Hi everyone,
I made a thread a day ago on this but no-one has commented. Seems there is lively discussion here on this topic so hope you don't mind me posting it here too!

I'm upgrading a 2017 27 inch iMac (EMC 3070) with a 1TB fusion drive. Wanting to upgrade both drives, and think I have the PCIe decision narrowed down to 2 drives, so would love feedback on which people like more!

1. ADATA XPG SX8200 Pro 1TB vs. Samsung EVO 970
2. Samsung 970 EVO 1TB.

And possibly considering

3. Intel 760p.
​

Seems no. 2 may be the more popular one. Seems it is the fastest, BUT, no.1 is cheaper and people say it runs cooler. They both have good endurance, which is where no.3 falls short, though people say no.3 is also cooler than the EVO.

Cool is good for me if this means the fans will be quieter!
And regarding speed, they are all such a quantum leap faster than HDD and even all a lot from SATA SDD, so I really doubt the speed difference between them will affect me much at all. But I don't know how much the heat difference is for real world use with an iMac. Think it will make a difference to the fans or life of parts?

I'm also thinking to upgrade the SATA drive to Crucial MX500 2TB, as discussed in a recent thread. Seems a good price, though, what do you guys think - if the stuff I use mostly is on one of these fast 1TB PCIe drives, if there any point in having a 2TB SSD on the SATA (for like movies, music etc.) or should I just go for an HDD? Perhaps there is no need to that, no effect for listening to music and watching movies, ebook library and all that? If so, any recommendations?

Thanks!

 

[ProteoMX]

About the HDD vs SSD for file storage: speed wise, you won't see any difference between them under that scenario. I have a similar setup (apps, system files, work folders, etc. are all in the SSD but my user's Movies, Pictures, Music and Download folders are actually symlinks pointing to folders in the HDD). Absolutely no slowdowns or noticeable speed degradation whatsoever.

But, SSD drives tend to run cooler and they *should* be somewhat more reliable on the long term, so if money is not an issue I'd go for that.

About the heat, I installed a Samsung 970 Pro nVME and so far temperatures are perfectly fine (around 50º most of the time). But, whatever you choose, I'd recommend to install a heatsink (I didn't and I regret it). It will help to keep the nVME drive cooler, they're cheap and easy to install so, why not?

 

[dobrink]

Both my upgrades were for client machines, as listed in the spec breakdown I gave.

Late 2015 would crash upon resuming from sleep, Late 2013 didn't throw any issues.

Edited to add: The Late 2015 was showing as an external drive, not just the Late 2013.
UK Based.

Was UK the origin of both machines, or can one of them have been imported from abroad? I am still on to this location-based theory as different factories may have used different boards, or upgrades may be applied differently from the region-based Apple servers. Otherwise, I do not know what can cause even some Late 2013 models to work fine, while most 2015 crash on wake. This external drive thing may be another lead, but what will cause the machine to list it as external? Or else, perhaps a combination of several factors, as nothing is true 100% of the time in either all issueless, or all problematic upgraded iMacs.

You’re definitely incorrect on this. I have a Late 2015 27” iMac with with a 2TB Sabrent Rocket installed that is unable to sleep without restarting.

Did you post your upgrade info already somewhere, can you link the post? We should refer to @mikehalloran for advice, what he thinks may be the cause of all the problems with wake. As him and @gilles_polysoft are the only ones who claim they have never experienced a problem with 2015 and later iMacs. We can provide them more information if requested, although here is quite a lot already.

I'm upgrading a 2017 27 inch iMac (EMC 3070) with a 1TB fusion drive. Wanting to upgrade both drives, and think I have the PCIe decision narrowed down to 2 drives, so would love feedback on which people like more!

1. ADATA XPG SX8200 Pro 1TB
2. Samsung 970 EVO 1TB.

I am using ADATA XPG SX8200 Pro 1TB in a Late 2015 iMac, the fan is constantly at the minimum 1200 rpm even under heavy load of Adobe AI, ID and PS, providing I also upgraded the CPU to the hotter i7-6700K. What I do not like about ADATA though is their poor customer service, Samsungs are more global, thus better supported and more reliable drives. Perhaps you can refer to the MacBook thread where people can actually feel the SSD during operation and there are a lot more upgrades and reference points from the more massive MacBook users, who have tested a far wider variety of drives.