RAM upgrade, black screen, do they need to be in specific slots?

iMas70

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Sep 4, 2012
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I picked up my new iMac today so I figured I'd add the 32GB RAM from OWC before I set it up. I did that, started the computer and was greeted with a black screen. Tried it a couple of times then removed the OWC RAM. It worked fine. I contacted OWC to confirm I have the correct RAM. Next I removed the factory 8GB and installed the two 16GB into the same slots (2 and 4). It worked fine. Then I added the factory 4x2 sticks into the 1 and 3 slots. Black screen. Do they have to be in specific slots?

Thanks!
 

Coco Nuts

macrumors member
Jan 1, 2016
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If you only use two RAM sticks, put them in slot 1 and 3. Slot 1 is the bottom slot, not the top slot.

Leaving the factory RAM out and only using the OWC RAM would be the most stable option.
 

iMas70

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I'll probably end up going that route. I really don't need more than 32GB so I could just close it up but it should work with all four sticks.
 

mikehalloran

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Oct 14, 2018
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The Sillie Con Valley
If you only use two RAM sticks, put them in slot 1 and 3. Slot 1 is the bottom slot, not the top slot.

Leaving the factory RAM out and only using the OWC RAM would be the most stable option.
Nonsense.

You need to match the RAM properly, that’s all. Bank 0 has one pair; Bank 1 has the other pair. The slots alternate 0, 1, 0, 1.

Follow the directions and make sure it’s seated properly.

https://www.ifixit.com/Answers/View/223429/How+to+couple+RAM+Modules+in+iMac+27
 
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iMas70

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I tried pairing them like that from the beginning (From the top - 16, 4, 16, 4). I filled the two open slots with the new RAM but it didn't work. Tried a few times. I misunderstood what you wrote when I first read it the first time so I changed the pairing to 16, 16, 4, 4. It works.