Imac NVME SSD Problems

[Pawnhawk]

Hi All, First off I am new to Mac's well in my case imac. This is complicated so please bear with me while I try to explain my problem.
I bought my imac which is 27" 14.2 imac with 16Gb ram and a 3Tb standard HD, it was running great but I thought I would like to get a bit more speed out of it.
So I did alot of research to see what my options were, and decided on a NVME SSD which would fit on the motherboard of my 2013 imac.
So I ordered a Samsung evo 970 500Gb NVME SSD and a Sintech adapter, well that what it said on Amazon, but am having doubts about it now.
The adapter does not say sintech anywhere on it, it only says M2 NGFF os 2013 -2017 macbook SSD RoHS.
So as I had got it I thought here goes and give it a try. Took the imac apart and finally got to the motherboard, fitted the adapter and SSD ito it's slot, put it all back together.
Switched on and mojave started up great as before off the 3Tb HD, started up disk utiuls great there was the SSD, so I erased the SSD to apple format.
Inserted mojave installer into USB slot, started mojave installer great everything seemed to go OK, found SSD and the whole process started. Now the fun begins the process of installing took 3 hours, I thought this does not seem to be right but let it go.
Once it finished and then restarted the imac great mojave started off the SSD, now the problems start, the dreaded fan was very loud, but before I installed the SSD fan controller I wanted to check temperature of CPU, all good was running between 30 - 40c, loaded SSD fan controller set to manual great fan went quiet. Loading software onto the SSD was extremely slow, far slower than the 3Tb HD.
Then starting the programs up was very very slow, the 3Tb HD was about 4 or 5 times faster than this SSD, so I thought I would do a speed test. Started up Black Magic and was getting just above 300Mb read and writes times, which I thought was not to bad, but why was it so slow. Did alot of research but could not find anything, except something to do with TRIM but when I looked it was on, so I was at a total loss.
I had a thought I had got and old 240Gb SSD, tested it and it was working OK, so did another strip down took out SSD and 3Tb HD, and replaced it with the old 240Gb SSD, put it all together again.
Switched on and the dreaded ? on screen, back to the PC for some research, but just as I switched on the PC and waited for it to start, the apple logo appeared on the imac so I left it to do it's thing.
Soon enough the Disk Utils started, went into disk utils erased the SSD to apple format, went to install mac os and great the mojave installer started, it only took 30 - 40 minutes to complete.
Restarted the imac and it started very quickly, installed a few programs and they all stated about 10 times faster than the samsung EVO 970 SSD. So I did another speed test for this 240Gb SSD and it came out with just above 200Mb read and writes times, so why was this slower SSD far faster than the Samsung EVO 970 SSD, I am at a total loss and don't know what to try next, so I am hoping that some out there has had the same problem as me or who can point me in the right direction.
Thanks in advance for any help you may have.

Pawnhawk

 

[mikehalloran]

If you also replaced the HDD, get the OWC Temp Sensor to fix the fan problem. The problem with software non-solutions is that now you have to control the fans manually plus listen to the fans go full on till the extension loads.

The 970 EVO will work on a 2013 but it’s overkill. The max bus speed is 1500. An Intel 660p or Crucial P1 is slower but still faster than the bus speed. The 970 is what you want for a 2015 or later with a PCIe 3 x4 bus.

Why your SSD is so slow makes no sense unless you really didn’t get the Sintech adapter. There are a number of other variables. I didn’t install it nor the OS nor set it up so I can only guess and I will pass on that, except...

If you didn’t format the blade APFS GUID before installing Mojave, that could be your problem.

 

[TwoH]

For the fan ramp - did you remove the Sata/power cable when you removed the HDD from your machine? If not, this is what causes the fan ramps on the slim iMacs.

 

[Pawnhawk]

Hi, thanks for the reply, no I did not replace the HD I left the original 3Tb HD that came with the iMac.
I did format the blade ssd to APFS GUID in disk utils.
The fan problem is with the ssd well I think so, there are no problems with temperatures at all, even when I took out the blade ssd and 3 Tb HD, then replaced with old 240Gg ssd there was no problem with fan all was normal. I think mike might have something with the adapter for the ssd, as it may not be a sin tech as it was advertised. One other thing I am unable to test the blade ssd in another machine just to make sure all is good. So I have sent for pc adapter to check it out. Unless anyone has any other ideas I will check in once it comes.