iMac 27 2020 memory upgrade

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map989 Author

Level 1

9 points

iMac 27 2020 memory upgrade

How to allocate different capacity memory chips? According to apple (quoted), the channels should be equal capacity, I.e., channel A (slots 1 and 2) should equal channel B (slots 3 and 4).
“iMac (Retina 5K, 27-inch, 2020) DIMMs have a notch on the bottom, slightly left of the middle. If your DIMMs are mixed in capacity, minimize the capacity difference between Channel A (slots 1 and 2) and Channel B (slots 3 and 4) when possible.”

I intend to add 2Xist 32 and leave the 8G currently installed if it is in 2x4.

Sound right?

Posted on Dec 5, 2020 5:24 PM

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Answer 1

rkaufmann87

Level 10

148,470 points

Dec 5, 2020 6:56 PM in response to map989

On a 2020 iMac installing upgraded RAM is pretty easy. If you are going to use the original 8GB DIMMs put those in slots 1 & 2 (the top 2 slots) and the upgraded RAM in slots 3 & 4. This will yield the best performance. When you buy your RAM only buy it from Crucial.com or Macsales.com, NEVER buy from a reseller such as Amazon or anyone else. Just Crucial.com or Macsales.com direct.

Below are pictures of my RAM installation, please pay close attention to the slots and speeds of the RAM!!!!!!!

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Answer 2

rkaufmann87

Level 10

148,470 points

Dec 5, 2020 9:00 PM in response to map989

I have tested both ways and my method works better. I've had this conversation with others, when folks follow my advice they get the right results. Do it Apple's way and your RAM will be slower, not that you will be able to tell but it will be slower non the less.

The proof is in the graphics I provided!

Your call though, it's your iMac.

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Answer 3

map989 Author

Level 1

9 points

Dec 5, 2020 8:27 PM in response to rkaufmann87

Thanks RK. But this contradicts the advice coming directly from Apple. Have you tested and measured performance both ways?

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iMac 27 2020 memory upgrade

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