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Mid 2012 model, A1278 / 2.5 GHz i5 or 2.9 GHz i7 processor.

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MacBook is slow after upgrading to SSD

My Macbook is much slower after upgrading to an SSD and performing a clean install.

Troubleshooting tips I have conducted:

  • Swapped back the original hard drive which confirmed that the cable is alright
  • Updated firmware to the latest available version
  • From recovery mode set the SSD as default startup disk
  • Reset NVRAM

To compound matters, the SSD seems to perform as expected when connected externally using USB.

I am well and truly stumped at this point.

Edit: For the sake of clarification, when I swap in the stock HDD it’s faster than the SSD. When I plug the SSD to a USB port and boot, the difference in performance is significantly noticeable.

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Just checking, but have you tried resetting the SMC? I see you have resetted the PRAM/NVRAM alr so I just want to make sure.

How to reset the SMC, PRAM and NVRAM on a Mac Laptop


I shall give this a go and report back.


Did any of these suggestions fix your problem? I'm in the same boat.


Apologies for the delayed feedback.

No luck after resetting the SMC. I know my hardware is working fine so I'll try a clean install and see if there is a difference.


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Yes, the cable may continue to work with the original HDD. Now that you are using an SSD, you will experience increased speed and efficiency and, in turn, increased temperatures. Your SATA cable is likely already in need of replacement, but due to the much slower HDD, problems will be much harder to identify/pinpoint. The issue is directly related to the placement of the SATA cable and the MBPs' metal chassis design.

I experienced identical symptoms with my MBP and replacing the SATA cable resolved everything. SATA cables are fairly cheap on Amazon (try to find one with at least a 1 year warranty). Additionally, I would recommend placing a strip of electrical tape to insulate the ribbon that comes in contact with the uppercase.

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Your issue is a known one, your HD SATA cable needs to be replaced as its damaged.

Follow this IFIXIT guide: MacBook Pro 13" Unibody Mid 2012 Hard Drive Cable Replacement and heres the needed part: MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable. You’ll need to place a strip of electricians tape on the uppercase where the cable crosses over as the rough surface wears the cable. In addition you don’t want to bend the cable sharply at the corners as the crisp bends damages the cable, instead you want smooth arcs. Do make sure you get a good quality cable as many on Amazon or eBay are junk.

MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable Image


MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable


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I did mention that the cable is the first thing that I tested. It works perfectly fine with the original hard drive.


Yes, I did see you wrote that! The thing is the cable you got was likely a cheap knock-off or was damaged. I find a lot of people tend to crease the bends a bit hard so the delicate foil wires get damaged as these are fragile from excessive bending. Do make sure you get the one I've listed as some folks are also selling the older 2011 models which are not SATA III (6.0 Gb/s) rated!


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