This may be a silly question because I'm not fully sure how RAM works and is loaded, however I'm trying to figure out a potential configuration here.

I have two RAM sticks that are both spec matched for my MBP. One of them is a 8gb gskill stick, and the other is a 4gb Samsung stick. I rarely use more than 8gb of RAM, however it does happen on occasion.

I would think that it would be best for me to fill the entire 8GB stick first, and then load data onto the 4GB stick if the 8 overflows. This said, I'm not sure if it's possible to load the sticks "one and then the other" like this, or if it would be beneficial.

Is the order that info is loaded into RAM determined by the slot that the stick is in? If so, which slot (top or bottom) should I stick my 8GB stick into in order to make sure that it's used before the 4gb stick?

1 Answer 1


Typically you want to install memory in pairs (i.e. two 8 GB "sticks" or 4 GB "sticks") to make use of something called the dual-channel memory interface. What that in essence means from your perspective is that the computer can use two memory modules at once, one in each "channel," if they are matched. That gives better performance than using one and then the other.

The way Mac OS X works, your computer will use all of the available RAM when it can to cache things that it might need later--even if you don't need them in RAM right at the moment. The price of RAM what it is today, I would try to order another module of the exact same type as your 8 GB.

Source: http://support.apple.com/kb/TA38415?viewlocale=en_US&locale=en_US

  • I echo @samh and would add that if it is not too expensive for your budget, get new matching RAM pairs from the same manufacturer - don't mix & match. This would mean removing the 8GB & 4GB RAM for spares, or to sell/barter.
    – IconDaemon
    Commented May 27, 2014 at 23:21
  • My question wasn't regarding running RAM in dual-channel. I understand this point and I actually have a matching set of 8G sticks, but I gave one to my GF for her MBP. So assuming I have the option of only running a single 8G stick or a mismatched 8 and 4, the 8 and 4 are better hands down. My question is does it matter which slot I stick them in? Is there a way I can use the 8G stick first, and then the 4G stick, that way the comp doesn't have a need to even use the 4G stick unless I exceed 8G of memory? Commented May 28, 2014 at 15:30
  • What's not clear to me is what problem you're trying to solve by "only using the 8 GB stick." I don't know how that Logic Board and OS X address memory in that respect, so I can't answer your question.
    – samh
    Commented May 28, 2014 at 17:14

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