Memory (RAM) for a mid-2020 27" iMac w/ i9 chip

Put the original RAM (I'm assuming you only got 8GB) in slots 1 & 2 (1 is the top slot, next in line is slot 2) and any upgraded RAM in slots 3 &4.

You won't damage the computer if you experiment with placement. However you will get the very best performance if you follow the advice I have provided. The speed difference is not noticeable but it is there none the less. If you do decide to experiment with the placement use the System Report app to look for the RAM's speed.

• No speed advantages on 16GB VS. 32GB DIMMs, mixing size DIMMS should not affect speed, however when installing always install matched pairs. For example, installing 2 x 4 GB + 2 x 16 (or 32) GB DIMMS is fine. What would not be okay is installing 2 x 4 GB and 1 x 32GB DIMM.
• Speeds are up to 2667 assuming you install correctly.
• No speed hit.

I only recommend to buy direct from the vendor (crucial.com or Macsales.com) as resellers do not always have identical DIMMS and many users have reported issues buying from third party vendors so why gamble to save $10. When users deal direct they are getting it right every time.

If you are on the Internet (which obviously you are) you can find bad reviews on almost anything, most are unfounded or user errors when dealing with reputable vendors. I can find lots of people on the Internet that tell me Apple makes junk, my (and millions of other users) can vouch they do not. Some people that have one bad experience will swear off a complete brand, I've seen people that had a bad interaction with a rep at an Apple Store then state all of their staff were idiots and they would never buy from Apple. Silly, of course and frankly folks like that I wouldn't want as a customer anyhow.

My standards of excellence come from over 30 years of experience as a OWC, Crucial, Apple and many other vendors customer. Believe me or don't believe I don't care one way or the other, that is up to you and I honestly am not offended if you don't. But then again, if you don't want to believe me then please don't ask.

I disagree as to where to install the additional chips: the original chips are either in 1 + 3 (meaning they are matched) with 2 + 4 open (or those two are filled). So, if you simply want to add 2 chips, put them in the empty slots. If you are getting 4 new chips, it makes no difference.

In older Macs, the alignment was not vertical (but horizontal), so you should put them in 1 + 2 (first row) and 3 + 4. Now the alignment is vertical and there is a reason Apple puts them in 1 + 3 or 2 + 4 because those slots will be matched.

That is what was suggested by Apple as well as OWC.

As for where to get them, I completely agree: I only buy from OWC. They are a Mac-centric vendor and the RAM is actually made for Macs whereas - except for the cirect Crucial site - other vendors sell RAM that is not necessarily made exclusively for Macs, but mostly for Windows. Of course, you can buy them wherever you like - it is your choice.

FWIW, I try to avoid Amazon - period. I don't like to do business with any behemoth whose corporate policies I cannot agree with.

As long as it works........

In the "old days", the slots/matching modules was far more important than it is now. On that, I do not know what Apple changed, but I was told that in the vertical arrangements 1 + 3 and 2 + 4 were the best "match". Anyway, that is how I have been doing it and have not had a problem either.

So, we'll file this one under "either will work"....

Totally wrong and I believe I answered your other questions.

Your welcome and I am not at all offended, just busy.

Your welcome.

Upgrading RAM on a 2020 27" iMac is EXTREMELY simple if you follow some simple rules. First only buy direct from a reputable source such as OWC (www.macsales.com) or Crucial.com. Do not buy from a reseller such as Amazon, Ebay, Newegg, Best Buy etc...

Next if your keeping the original RAM installed, please only place that RAM in slots 1 & 2 (the top 2 slots). Then install the matched RAM (2 x 16GB or 2 x 32GB) in slots 3 & 4 (the Botton 2 slots). Why, simple installing any other way will reduce the speed potential of the RAM. Please pay close attention to the photos below that show the slots used and the speed achieved by using these slots:

Its that simple if you follow these steps!!!!!!!!!!!!! This is not rocket science and if you want to get to 64 GB I strongly recommend using the original 8GB of RAM and then buy 2 x 32 GB of Macsales.com or Crucial.com RAM and retain the original 8GB and that will give you 72 GB of total RAM.