Which memory slots to install additional memory

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Which memory slots to install additional memory

I'm purchasing a new iMac27" 2020 with base memory of 8GB which I understand comes as 2x4GB modules in slots 2 & 4 (DIMM 0). I have purchased an additional 32GB of RAM (2x16GB OWC RAM modules) to bring my total memory to 40GB. My question is where to place the 2x16GB modules? Some videos have said to put the new modules in the 2 open slots (1 and 3) and at least one video from Mac 9 to 5 said you should move the original RAM to slots 1&2 and install the new modules to slots 3&4 to get the maximum memory speed. They said that if you leave the 4GB in slots 2&4 and put the new RAM in slots 1&3, the memory speed will be 2133 MHz as opposed to 2666 if the 4GBx2 is in slots 1&2 and the 16GBx2 in slots 3&4. I'm looking for clear direction on this.

Posted on Aug 17, 2020 2:25 PM

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Answer 1

Top-ranking reply

Malcolm J. Rayfield

Level 7

23,095 points

Aug 17, 2020 6:28 PM in response to stansil

The slots used can make a difference.

https://9to5mac.com/2020/08/09/how-to-upgrade-2020-imac-ram-video-5k-27-inch-128-gb/

"Instead, I found that it’s best to install two like modules in slot 1 and 2, and the other two like modules in slot 3 and 4 for the best performance. Notice how the same memory configured in this arrangements results in the proper 2666MHz (2667) speed rating."

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Answer 2

rkaufmann87

Level 10

148,488 points

Aug 17, 2020 3:54 PM in response to stansil

You can test it the same way 9 to 5 did and find out for yourself. Most experienced users simply populate the empty slots and forget about it. The difference in performance (if any) would be some minuscule that you won't notice it.

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Answer 3

stansil Author

Level 1

14 points

Aug 19, 2020 1:11 PM in response to Malcolm J. Rayfield

Thanks Malcolm,

I just got this email from OWC stating the same thing you said:

"We spoke about your new 2020 iMac and purchasing extra memory/ram for it and the best configuration to ensure the fastest speed. Upon further review of this, I would recommend placing the Apple memory and OWC memory side by side. So you can rearrange the memory in this order to ensure optimal 2666Mhz performance:

Slot 1 APPLE

Slot 2 APPLE

Slot 3 OWC

Slot 4 OWC"

So that's what I plan to do.

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Answer 4

stansil Author

Level 1

14 points

Aug 17, 2020 4:52 PM in response to rkaufmann87

Thanks, that's what I planned to do. I did a chat with OWC and that's what they said but they didn't seem very definitive.

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Which memory slots to install additional memory

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