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Hi guys. I decided to upgrade my MacBook Pro Mid 2012 to SSD. I bought a Kingston A400 480 GB SSD to swap with the old HDD. I have with a USB adaptor downloaded Mac OS Catalina with my already installed HDD. I can boot to the SSD’s Mac OS through the USB adaptor, but can’t boot to it with the internal SATA connector (I get the blinking folder error). I can boot to my HDD’s Mac OS through the SATA port, and I don’t really get that. I have swapped the original 4 GB of RAM to 16 GB, and yes, I have already tried both combinations with my SSD, it works with the HDD. I see that alot of people suggest the cable could be bad, but I don’t get that since the HDD works with it? I have also tried the CMD+Alt+P+R combo with no success. I have tried an SMC reset also. Do anyone have a suggestion, I feel like I have tried everything with no success at all. Best Regards. Tobias
Sadly, you do have a cable issue. Let’s think this like a car … You are on a windy road in your Ford van going about 50 MPH which is the limit of the road. A nut passes you in his Porsche 911 going 80 MPH, just up ahead you see the guard rail broken through. Guess he will be making his maker! :-() So how does this apply to the cable? The data running down the cable is like your two autos on a windy road, the slower 50 MPH makes it, the other 80 MPH doesn’t. Apple originally used a SATA II (3.0 Gb/s) rated cable which was able to support the data I/O the original HDD dealt with, later Apple upgraded the cable to SATA III (6.0 Gb/s). We also have a quality issue with the cable and if not handled properly can become damaged both of which can effect the ability of the cable to work as intended. Your Hard Drive Cable Is A Ticking Time Bomb which gets into the quality of the cable and applying a strip of electricians tape on the uppercase where the cable crosses. Here is the proper cable MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable and here’s the guide MacBook Pro 13" Unibody Mid 2012 Hard Drive Cable Replacement The last issue is cable folds! We don’t want a sharp fold at the locations where the cable needs to bend around. We want a smooth arch. The easies way is to find an old BIC ball point pen take the ink straw out and use it as a forming break to help you create the needed radius. Even after doing all of this I do recommend you reformat the drive and install a fresh OS onto the drive as we want to make sure there aren’t any corruptions.
