I’d like to know if there’re any side effects to these memory configurations for MacBook Pro mid 2012 (I guess this can be extended to any Macs with removable memory).

Doubt 1: any side effects if I use slower or faster memory?

Doubt 2: should I use different sized modules, such as a 4GB in one slot and a 2GB module in the other?.

Doubt 3: can I mix the speeds (such as 1 memory slower than the other).

Doubt 4: is dual channel used in the 2012 Macs? (I can’t see this stated in support.apple.com/specs)


Only two MBPs match your description, and they both require:

204-pin PC3-12800 (1600 MHz) DDR3 SO-DIMM.

Either MBP 13" & 15" can take 16 GB (actual) but are equipped by Apple with 8 GB.

Simple answers:

  1. Use the RAM speed the MBP was designed for (in this case 1600 MHz.)
  2. You can use differing sizes, but performance will suffer as interleaving (dual-channel) will be disabled.
  3. Do not mix speeds (see #1.)

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