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I need some help, I purchased a 850 EVO SSD which I can format externally using a thunderbolt case. I formatted it: Mac journal/partition1/GUID base for Mac but when I put the SSD inside my system the disk was not formatted properly so I can’t install a fresh copy of the OS. I need some help pls
This series does have a fragile SATA cable. At this point I would replace it. Here’s the IFIXIT guide to step you though whats needed: MacBook Pro 13" Unibody Mid 2012 Hard Drive Cable Replacement and here is the part you need: MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable Apple PN 923-0104
Once you’ve replaced the SATA cable, as Dan suggests, then reinstall the SSD, attach the old HD through your Thunderbolt case, and format the SSD through the internal connection. Once that’s done you should be able to install a new OS on the internal SSD. The problem you’re describing (SSD formats externally, but doesn’t mount on the internal SATA bus) is a common problem with Mac laptops from about 2008-2011. Damaged SATA cables are often part of the problem; if you replace it with a brand new cable (not just a newer used cable), that often resolves the problem. Samsung SSDs such as the 850 have a reputation for being more fiddly on Macs than other SSDs such as OWC or Crucial/Micron. But typically, 2012 and later MacBook Pros will usually work with any SSD, as long as the SATA cable works properly and the drive is correctly formatted. What operating system are you using? For a newer drive like this, later is better. I think the oldest OS you should be using is probably Mavericks/10.9.5.
Actually there is two kinds of problem when trying to boot from SSD plugged in the internal SATA (even if the system can boot on the SSD in USB): IF YOUR COMPUTER IS BOOTING, but you can’t log in and you stucked in the “no entry sign” = “Prohibitory sign”. => you made a wrong copy of the disk! Redo the job with CCC and no options, add a recovery partition => choose to boot from SSD IF YOU COMPUTER IS NOT MOUNTING THE SSD : you get a question mark “?” at startup, then, it is a problem of cable. => change the SATA cable.
