Upgrade RAM

hmhhh ... Now I am confused.

There is a big discussion on https://de.ifixit.com/Antworten/Ansehen/223429/How+to+couple+RAM+Modules+in+iMac+27

So best is to have equal capacity paiered as I understand, like 2x 8+4 GB

And now we are talking about BANKs (wich should be channels) and DIMMs

So should each pair consiting of 1 4GB and 1 8GB stick be stuck on equal BANK or equal DIMM.

As far as I understand it should run on equal DIMM.

The delivered config is shown in the screenshot in post #1.

Equal capacity (4GB) split over 2 BANKS but paired on the same DIMM.

2x 4GB run on equal DIMM one per BANK.

That would be to my understanding either A or B.

Equal amount of GB 4+8 per DIMM and not per BANK.

Sorry to be a pest I simply didn't get it yet.

please do not get me wrong, I just would like to understand it

you write pairwise causes loss, ok d'accord

but is pairwise when we talk about 4 sticks, the pair of 2 equal sitcks or the pair of total ram per pair

like 4 and 4 make a pair, 8 and 8 make a pair

or 4+8 makes the pair

and shall the not equal pair referr to equal dimm or equal bank

I understand https://de.ifixit.com/Antworten/Ansehen/223429/How+to+couple+RAM+Modules+in+iMac+27

that majority referrs to euqal amount of ram (4+8) per DIMM and not per BANK

which would be exactly A or B

and once again, pairwise per DIMM and not per BANK is how apple delvered that iMac in 2013 to me see screenshot in post #1, would that mean apple already shipped it with wrong combination?

8GB 2x 4GB both on same DIMM and split on per BANK 1 stick

thats what makes me confused

so makes the BANK a pair of equal sticks or makes the DIMM a pair?

Cheers I know that doc but either I didn't get it or the doc does not specify the answer to my question.

As written I have an iMac 14,2 (late 2013 model) running High Sierra a.t.m.