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I have a 2012 MBP with a I7 and 8GB of RAM. When I first bought it, it was running with a 2TB HDD but later on, i replaced it with a 240GB SSD. It worked really well for the first few months but after 5 months if stopped working at all. After some research I figured this could be related to me not having switched on TRIM on my MacBook, this was backed up by the fact that even when i tried to read the drive externally (while booting in recovery mode) I saw that every byte of the drive was full. Due to that I got tried putting in my original hard drive in my laptop. At this point i suspect the SATA cable failed, a common problem on a 2012 Macbook Pro’s. I got a replacement one and I installed it but the laptop still doesn’t read any of the drives. It won’t even recognize my 240GB SSD and while it will see my Mac’s OS-X boot on my HDD (running Yosemite) it won’t boot into it and keeps giving me a circle with a cross going through it. Any help would be very much appreciated
Thats the prohibitory symbol! If your Mac doesn’t start up all the way When you swapped your drive around you confused your system. You’ll need to boot up under the Startup Manager using the Option (⌥) key at startup so you can select the proper drive, then go into your Preferences to alter the Startup Disk. Reference: Mac startup key combinations
