I am pretty sure that it is not the EVO 850 but the copied and mostly erased software that causes your problems.
You should do a fresh install…. and in future times start to do backups regularly - in case of a failing drive.
If I were you I´d try a fresh install.
During the past years I cloned half a dozen Samsung 840 and 850 SSDs and installed them on 2011 and 2012 MBVPs never ever had a problem and the speed of the Samsung SSds is top.
To exclude a problem with the Disk cable you can just put a well-working HDD in your 2012 MBP for a test:
If it runs well, it might NOT be a problem with the cable. If you have the same problem with a different SSD or HDD it IS the cable.
If your cable is the reason for your problem, there is a good chance that your old HDD is NOT broken but suffered also from the cable!
Did you try to start from your old HDD when it is installed in an external USB housing?
If this works, the cable is the only problem.
edit:You can also use Disk Utility to test the SSD.
I never saw problems with the hardware on SSDs, but often lots of problems with rights of user accounts and so on. Luckily, this app can not only test the hardware but repair as well most of the problems caused by not fully erased apps, disturbing User accounts and User rights and so on…
IIRC you can do this also with an other Mac using a USB exterior drive enclosure (but it will last long because of the low data transmission rate of the USB connection…)
another source might be failing RAM: Even if the self-test after starting the MBP shows "ok", there might be problems with the RAM.
Easy to exchange RAM with another machine just to make a test for excluding RAM problems… if your machine works fine with other RAM than yours…
Another beautiful app is etrecheck: Free and runs a lot of diagnosis…
OnyX is very good as well…. cares also about user rights...
(…)
- That's really not a very good test. Failing SATA cables often work perfectly fine with HDDs but behave bizarrely with more demanding SSDs. The test should be done with another SATA III SSD if it is to yield any usable information.
I agree with you. But you can at least identify a completely or nearly completely broken ribbon cable.
it is for that that I was prudent and only wrote:
To exclude a problem with the Disk cable you can just put a well-working HDD in your 2012 MBP for a test:
If it runs well, it might NOT be a problem with the cable. If you have the same problem with a different SSD or HDD it IS the cable.
I did not have enough time to write more and because I wrote (wrongly) also about "excluding" ribbon cable failure in the sentence before it was very easy to misunderstand me. my fault. I did not have the time to search and link the videos neither, now I did this.
What I wanted to say: if a second HDD or SSD (which works well in an other machine) works NOT for booting, you can nearly be sure that the ribbon cable is the problem. If it works,
True that - had this problem in my old 2009 MBP. Cable worked OK with a HDD, lots random errors on an SSD. Shielding the cable (first used aluminum foil, then an adhesive copper tape) helped, and it worked fine for a few years (and the SSD still works in wife's PC laptop).
This was risky: The problem with the ribbon cable is not at all a shielding problem, it is a sort of micro-short circuit.
The reason is too thin isolation around the multiple copper fibres in the cable - and the reason for that is bad design: while the EXTERIOR SURFACE of the MBP is well-treated, the INTERIOR is NOT. On a microscopic basis the interior surface is like a nail file - so it is only a question of time that the too rough interior metallic surface is degrading the too thin isolation of the ribbon cable… the only solution is isolating the ribbon cable (with gaffer tape on the inner surface under tha ribbon cable and/or on the ribbon cable itself for example) - which can save an old cable for a certain time - but can be done already as a prophylactic strengthening method for the ribbon cable to prevent problems with the ribbon cable. I think that problems with the ribbon cables will more often happen if the MBP had a HDD in it for some time - because of the multi-millions of micro-vibrations of the mechanical drive (spinning wheel) and will be less often or maybe nearly never happen with MBPs assembled from the beginning on with SSDs (no micro-vibration).
There is a really excellent video about the main problem (the nail file-like metal surface is demonstrated at 0:40):
the "first aid" and the prevention of failure:
gaffer on the metal surface-method:
Another (a bit less elegant, but also effective) method
is the "gaffer on cable-method" :
.
[doublepost=1459530955][/doublepost]I must say that I am disappointed that the OS already got advices in january for the same problem… but he don´t like neither to give feedback to persons helping him nor telling everything about the first attempt here in this new thread (why didn´t he continue the old one??) ..
https://forums.macrumors.com/threads/how-to-transfer-my-hard-drives-files-to-an-ssd.1952382/
so - I am out. It´s wasted time...