adding memory to late 2012 iMac 27"

Just put 32gb in mine 27 imac 2012 u can scan your imac with

CrucialMacScannerUK.app/

Addendum to my post:

Checking my slots this morning, they show up exactly as previously noted - yet they are matched horizontally:

So, IMHO, it is Apple's slot numbering system that is confusing - they are still installing them to match horizontally (matching the left and right slots) because doing so results in better performance.

In the new 27 iMacs the memory is stacked vertically. The 4 slots are one on top of the other.

Thanks for that info - I had not had an opportunity to see that. So there is no more "matching" to do? Oddly enough, OWC still says "Install Pairs (2 at a time) for best performance, but makes no mention if they should be adjacent? And, their install video makes no mention either.

From what users who have the system are saying is that Apple is installing in 1 & 3 (I believe that would be the top and 3rds slot down).

Assuming Apple knows what they are doing 😮 then it appears that the 'matched slots are the two odd and the two even slots (!&3 and 2&4)

But as I wrote previously, one for the pairs to be 'matched' requires more then just the same size sticks. Even buying two sticks of the same size at the same time will not ensure matched memory and two the increase in performance will be such that normal users will not see any real difference.

regards

I had the same dilemma. I too assumed Apple knew how to assemble their macs but thought maybe if you only have two slots filled the put one in 1-2 and one in 3-4 to represent both sides equally but then when adding ram to reposition them in 4GB 1-2 and 8GB in 3-4.

Turns out that apple care informs me it makes no difference as the logic board sees them and makes its own "matching" arrangements.

I asked if I should revert to apples original placings and was told catagorically that she has checked with a supervisor and it makes no difference so although it's playing havoc with my OCD I'm not risking breaking, bending or static frying anything by doing it all again

Checked the Apple logo-about this mac-more info- memory graphic and it states 24GB installed, all slots filled with no error messages anywhere 😁