Mixing RAM/RAM configurations 2017 iMac

[TitanTiger]

I have a 27" iMac (2017) that has the stock 8GB of RAM, slotted like this:

I found a good deal on a stick of Crucial 16GB that was open box on Amazon and snagged it. What is the best way to do this? If I put the new stick in slot 2 (BANK 0/DIMM1) for instance will that work properly or will it mess something up? Or would it be better to yank both of the existing sticks out and just put one 16 GB stick in?

 

[velocityg4]

Should be fine if you just add it. RAM will drop to single channel mode. But the benefits of 24GB in single channel outweighs 8GB in dual channel. I see no reason to remove the existing 8GB. As it is unlikely to conflict with the new memory. Which is pretty easy to determine since it won't boot. In which case you pull out the other memory.

Just be aware. Memory can require some force to install. So, if it doesn't boot. You may not have inserted it fully.

 

[wilberforce]

The first 4+4 GB should run in dual channel, and the remaining 16GB in single channel.
This is what is known as flex mode.

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[glenthompson]

My wife’s 2017 iMac had problems mixing the Apple ram with 3rd party ram. 3rd party ram works fine on its own. Try the 24gb and if you have issues, just drop back to the 16 you added.

 

[TitanTiger]

I ended up getting 32gb of RAM (two 16GB sticks) from OWC. Is there any problem with the slots I put it in? Again, this is 2017 iMac 27" (iMac 18,3).

 

[velocityg4]

I ended up getting 32gb of RAM (two 16GB sticks) from OWC. Is there any problem with the slots I put it in? Again, this is 2017 iMac 27" (iMac 18,3).

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It's all working and recognized. So, no there is no problem with the slots you used.

 

[TitanTiger]

It's all working and recognized. So, no there is no problem with the slots you used.

Ok. I saw some note on the 2020 iMac that said to try and minimize the size difference between the modules in slots 1 and 2 and the ones in slots 3 and 4. But it didn't say that for the 2017 so I just wanted to double check.

 

[velocityg4]

Ok. I saw some note on the 2020 iMac that said to try and minimize the size difference between the modules in slots 1 and 2 and the ones in slots 3 and 4. But it didn't say that for the 2017 so I just wanted to double check.

If you're worried. 9 to 5 Mac is showing a screenshot of RAM just like yours in the 2017.

How to upgrade RAM in the (Mid 2017) 5K iMac and save up to ~$900 [Video] - 9to5Mac

I recently acquired the base model Mid 2017 5K iMac, and I have a post in the works that explains...

9to5mac.com

I expect whatever you came across means BANK 0, DIMM0 should be close or better yet match BANK 1, DIMM0. Along with BANK 0, DIMM 1 matching BANK 1, DIMM 1. Which yours does.

 

[wilberforce]

Agree, your slot order is good

 

[wilberforce]

Ok. I saw some note on the 2020 iMac that said to try and minimize the size difference between the modules in slots 1 and 2 and the ones in slots 3 and 4. But it didn't say that for the 2017 so I just wanted to double check.

Correct, on 2020 iMac (which I have) it is has a quirk where memory speed degrades unless all slots have exactly same size sticks.
There is no such quirk for other iMacs. Your slot order is good