I have an early 2011 MacBook Pro, and my sister has a mid-2012. I've already seen the suggested duplicate possibilities that say that just swapping the hard drives shouldn't be problematic, but I've got another layer: I've got 10GB of RAM, an eBay-bought 8GB module and one of the OEM 2GB modules, that I'd very much like to keep.

Wikipedia says the two generations have different RAM specs - the early 2011 has "1333 MHz PC3-10600 DDR3 SDRAM, Voltage 1.5V" and the mid-2012 has "1600 MHz PC3-12800 DDR3 SDRAM, Voltage 1.35V." I'm going to take an educated guess that mixing frequencies/voltages won't end well, but what if I swapped the pairs of RAM modules? As in, what would happen if I were to put 10GB of RAM designed for early 2011 into mid-2012 and 4GB of RAM designed for mid-2012 into early 2011?

  • Nothing would happen, other then the old ones not working, but you can try. The 1333 MHz is just much slower than the 1600.
    – Ruskes
    Commented May 7, 2015 at 4:39
  • @Buscar웃 What do you mean, the old ones not working? I need both computers to be fully functional after everything.
    – user24601
    Commented May 7, 2015 at 4:41
  • Maybe I did not understand, are you mixing the old and the new RAM ? If you put faster RAM in a slower machine there is no problem with that, however the opposite might be a problem. means if you have slower RAM on a faster machine you might see some slowness.
    – Ruskes
    Commented May 7, 2015 at 4:42
  • @Buscar웃 Mixing the two different sets of RAM wasn't my plan, since I think I remember reading things saying that that's a bad idea. I'm planning to take all the RAM currently in the 2011 (1333 MHz PC3-10600) and put it in the 2012, and take the 2012's 4GB of 1600 MHz PC3-12800 RAM and put it in the 2011.
    – user24601
    Commented May 7, 2015 at 4:45
  • What do you think is better, 4GB of faster RAM or 10GB of slower RAM?
    – user24601
    Commented May 7, 2015 at 4:47

1 Answer 1


The RAM speed won't be a problem, the system will detect the speed of the RAM and run it at the maximum compatible speed. Hard drives also won't be a problem. (you will want to do a "fresh" install of the operating system)

As for the RAM voltage, I think that would be a problem. I'm not completely sure though. Whatever you do, make sure you run the Apple Hardware Test and babysit the machine while its running. Chances are if it passes all the tests, you're good.

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