iMac 27 doesn't boot with 4 Ram slots filled

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Level 1

4 points

iMac 27 doesn't boot with 4 Ram slots filled

Hi all,

iMac 27 2019. Trying to upgrade with installing the identical 2x4GB Ram modules (OEM Apple) to the 2 available slots. Followed the instructions from apple support but the iMac won't boot up after.

The iMac will boot up though with the 3 out of 4 modules installed, regardless of slot combination installed (not slot damaged) or modules combination (not module damaged).

All four modules are same (Apple 4GB OEM pre installed on iMac 2019).

Can anyone help me?

it doesn't make sense :)

Posted on Feb 3, 2023 05:06 AM

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Answer 1

Top-ranking reply

Ronasara

Level 6

15,465 points

Feb 3, 2023 07:32 AM in response to grigorios83

Apple computers are very picky about RAM. If something about a module is not right, a problem such as yours can occur. I think you have a bad RAM module. I would return it for a replacement. You were smart to move them around to confirm that it is not a slot issue.

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Answer 2

grigorios83 Author

Level 1

4 points

Feb 3, 2023 11:50 AM in response to HWTech

I acquired them online. They are identical to what the imac had inside.

They do work yes. If I pair them alone or with a 3rd one of the pre- installed, it does boot regardless of their slot order. I have tried various combinations to find any correlation but no. The only hint here is that sometimes, it won't boot up with 3 installed regardless of their slot order or modules picked but only sometimes. Attaching a photo with 2 modules and their S/N that differentiates the pairs.

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Answer 3

Old Toad

Level 10

214,242 points

Feb 3, 2023 02:02 PM in response to grigorios83

As you've already been made aware of Macs are extremely sensitive to the quality of RAM modules regardless of what is said about the specs of the modules.

There are only two vendors that guarantee their modules will work in the Mac intended as they test them in that Mac: Crucial.com and OWC (MacSales.com).

I would return the two 3rd party modules and order replacements from either of the vendors I mentioned previously.

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Answer 4

grigorios83 Author

Level 1

4 points

Feb 4, 2023 10:30 AM in response to Old Toad

Yes, I did. They are very often get loose once your push them inside, indeed. I have made sure each time that they are well seated.

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Answer 5

HWTech

Level 9

66,686 points

Feb 3, 2023 08:52 AM in response to grigorios83

How did you acquire these other two memory modules? It sounds like at least one of these "new" memory modules is defective. How do you know these are Apple OEM memory modules? Post a picture of the "new" modules (label side). Are you sure they are compatible with this iMac?

Do the two "new" modules work Ok if they are the only two modules installed?

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Answer 6

grigorios83 Author

Level 1

4 points

Feb 3, 2023 09:27 PM in response to Old Toad

Thanks for the answer but those are not 3rd party modules. They are OEM parts from another iMac 27 2019 and they work independently. So, to conclude all the 4 RAM modules involved in this case are Apple OEM parts with identical specifications.

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Answer 7

grigorios83 Author

Level 1

4 points

Feb 3, 2023 09:50 PM in response to Jack-19

Hi Jack, thanks for your answer. I bought them used. Would they work in a Mac if they were defective or counterfeit? Those are working seamlessly if they are installed alone (or with a third module). The problem occurs when all 4 are installed together.

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Answer 8

grigorios83 Author

Level 1

4 points

Feb 3, 2023 10:29 PM in response to Jack-19

No. It can happen with any slot and with any module. I have tried numerous combinations but it doesnt add up. All slots and modules are working, everywhere in any order but not all together. As i mentioned in a previous comment, few times it doesnt boot up even with 3 modules but again regardless the combination. In similar occasions with other pc brands there are issues related to BIOS and firmware.

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