SSD in MacBook Pro 2012 running full speed with new drive cable
Ron Lamb -
Original HHD was slow/hanging, so I replaced it with a 480GB SanDisk SSD. Initially, everything worked with original drive cable, but then I began seeing hangs followed by the white screen/X-circle after rebooting. I tried a replacement cable from another source which didn't work. Then I called the Apple store and other repair shops . They said they were not authorized to sell me a cable until they looked at my Mac to make sure there weren't any "other problems" (2 week backlog), so I decided to try iFixit.
The cable was brand new and has a newer part number than the original cable (for SSD I believe this is the key -the old 821-1480-A doesn't work). It took about 20 minutes to install. The MacBook came right up - actually faster than it ever did on the original cable. No hangs when using a video processing app. It has been running flawlessly for about a month now.
Be careful bending the cable (2 bends)where it goes under the drive and the support bracket. Follow the marks on the reinforced area of the cable and gently pre-bend before installing the screws. Don't press down the adhesive cable until all the screws are in to keep it from puckering.