Single rank vs dual rank memory for 27" i7 iMac

Do yourself a favor and stick with either cruical or owc for memory. I like owc, the stuff has a lifetime warranty, and you can rest assured that it will work with your mac. In fact, I had 8 gig go bad after 18 months in my wife's mac and they are replacing it.

You may be able to use either one (single versus double). Rank has to do with how the memory is organized for the controller. It is not good practice to mix dimm's of different ranks. Unless someone here has tested the exact memory you are considering, I doubt you'll get a solid answer. That is why I recommended two companies that garrantee their memory will work with your mac.

That looks right. I usually just hop over to owc since you can pick by mac model. Late 2012 27"

http://eshop.macsales.com/item/Other%20World%20Computing/1600DDR3S08S/

good luck

I'm using it as a reference, just look at the specs. I think the cruical you listed is right.

Technically, you can mix any size RAM DIMMS (2GB, 4GB, 8GB etc) in either bank or across banks as long as they meet Apple specs (appears to be 1600MHz DDR3 in your case)

However it is not good practice to mix different sizes in the same bank. If the DIMMs are matched pairs (ie the same size 2GB, 4GB, 8GB etc) memory speed will be optimized/maximized. If they are not matched, memory access speed is reduced because there is more overhead to access a non-matched pair.

So, your idea of 2x4GB in Bank 1 + 2x8GB in Bank 2 will be fine. Just don't mix them up as 4GB + 8GB in each bank, even though it works out to the same total amount of RAM.

Don't worry about single vs. dual rank; and in any event you shouldn't mix them. You may want to pull the existing DIMMS out of your iMac to see what they are. Look on the label - it will start with either "4GB 1Rx4" or "4GB 2Rx4". The number before the "R" indicates whether it is single or dual rank. I'd get the same spec memory as what came with your iMac. Go to crucial.com and have it scan your new Mac and it will tell you exactly what RAM is compatible.