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macrumors newbie
Original poster
May 30, 2019
my mid 2012 macbook pro model no.A1278 is starting to be incompatible with things like the latest google chrome and other programs. I'm guessing I should buy a 250gb SSD on ebay then install High Sierra onto it.. I've replaced the SETI cable in the past so i'm confident about replacing the drive, but i'm not sure how to go about updating the OS onto the black drive, and transferring files and programs from the old drive. I'd really appreciate any advice or help you could give, thanks so much!


macrumors 604
Dec 19, 2004
Just clone it then update to the latest MacOS. Use Carbon Copy Cloner or SuperDuper. They both work fine.

You can get a cheap 2.5" SATA USB enclosure online. Use that for cloning. Then you can swap the drives and use your old HDD for backups.

For the OS. I'd use Catalina if all your software is supported. Otherwise use Mojave. While you are at it max out the RAM. MacOS loves lots of RAM.


macrumors member
Feb 24, 2018
I also have the same 2012 MBP model. Years ago I went with this suggestion I saw online (and I paid someone to do it because I've never tinkered inside a computer much), to keep things cheap and maximize storage:

1. get a 250 GB SSD drive to replace the spinning 500 GB hard drive

2. ditch my DVD drive altogether since I never use it (or turn it into an external USB 3.0 one if you must have a DVD drive)

3. move my spinning 500 GB hard drive to the DVD slot with a hard drive caddy

4. I got 8GB RAM. I read that this model can work with 16GB, but that Apple doesn't officially say that, and it drains battery faster. My computer is fast enough with 8GB so I think that's enough for your average computer user

5. I stayed on Sierra for two years, then skipped High Sierra and am happy with Mojave now. You still can use 32 bit apps, and I have no use for any of Catalina's features. I have the equivalent feature with Sidecar with Duet Display, and Sidecar doesn't even work with our 2012 MBP anyways


The issues I've had over the years with my MBP is that on two occasions the hard drive cable died, and when that happened the bootup screen showed me a "no entry" sign. Initially the Apple Genius Bar guy told me my hard drive had died, but a non-Apple repair shop discovered it was just the hard drive cable that died. He still charged me a lot to replace that :(

Another time it would beep a few times on bootup and get stuck there. It turned out that somehow the RAM chips popped loose, so the repair shop put them back in for me. This time they did it for free :)


macrumors newbie
Original poster
May 30, 2019
ok so for the time being i'd just like to change the OS from 10.7.5 to Sierra. I've already downloaded the Sierra.dmg and ran the installation but nothings changed.. not sure where to go from here.. any ideas?
actually i think i've figured it out.. just had to run the installer that was in my applications folder!
this page helped >>


macrumors member
Feb 24, 2018
I read that Apple supports the current version of macOS and the two previous versions with security updates, so that would be Catalina, Mojave, and High Sierra.

This means Sierra is no longer supported with security updates. Keep that in mind if you're staying on Sierra.

If you decide to go from Sierra to Mojave like I did, of course first back up. When I made the upgrade from Sierra to Mojave, which involved converting the SSD format from HFS+ to APFS, the update process took a bit more than 2 hours, so just be patient and let it do its thing.


macrumors Penryn
Feb 20, 2009

You already know how to open the MBP and access the drive.
Everything else is easy.

Here's what you need, and what to do:
1. Get an EXTERNAL USB3 2.5" enclosure, like this:

2. Download CarbonCopyCloner from here:
CCC is FREE to download and use for 30 days -- this won't cost you anything.

Once you have these things, do this:
3. Put the SSD into the enclosure (for now).

4. Use Disk Utility to format/erase it to
- APFS (if you're using Catalina or Mojave)
- Mac OS extended with journaling enabled (if you're using High Sierra or earlier)

5. Now launch CCC:
- Accept all CCC's default settings
- Use your internal drive as "the source".
- The external SSD is "the target"
- Click the "clone" button and follow through
CCC will clone the contents of the internal to the external

6. When done, DO A TEST BOOT:
- Reboot
- Hold down the option key CONTINUOUSLY until the startup manager appears
- Select the SSD with the pointer and hit return.
- The MBP should boot from the external SSD

7. If the test boot looks good, now it's time to power down. Swap the drives around.

8. Now, boot again, and again use the "option key trick" in step 6 above.
- Do you get a good boot?
- If so, open the startup disk preference pane and set the SSD to be the NEW boot drive.

9. Finally, power down and do a test boot, this time WITHOUT USING the option key. You should boot to the login screen or the desktop.

I'd leave the old HDD in the enclosure, and use it for a backup or extra storage.
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