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A1418 | EMC 2889 | Late 2015 | 1.6 GHz dual-core Intel Core i5 or 2.8 GHz quad-core Intel Core i5. Released October 13, 2015.

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Display cable different between 1.6 and 2.8GHz logic boards?

I have a couple of late 2015 iMacs with the 1.6GHz i5. After looking at the insides and photos on eBay of 2.8GHz logic boards, I decided to take a chance and buy one.

Replacement went smooth thanks to ifixit’s guides, but when I got to the display data connector, the connector on the 2.8GHz board is approximately 3mm wider than the one on the 1.6GHz board, and my display data cable does not fit. I can boot the machine on an external monitor to confirm it is a 2.8GHz board, non-4K, but of course it’s throttled heavily due to the temperature sensor being disconnected.

EveryMac claims that there’s no difference in the displays between the 1.6 and 2.8GHz 21.5” late 2015 iMacs. They also say the “Retina” machine in this line is the 4K 21.5” imac. I can’t find anywhere else that says the 2.8GHz logic board uses a different display. I was kind of hoping to get another year or two out of these machines and now I can’t bring myself to put a sub-2GHz CPU back in it.

What did I do wrong? Why are the connectors different sizes? Is there some sort of adapter to connect my smaller data cable to the larger connector? Why is the connector larger if it uses the same panel? Buyer pays return shipping! I need your help. Thanks.

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Sounds like you are trying to use a 4K logic board within a standard retina system!

The older Retina display/cable is not designed to support the added data lines needed to support the newer 4K data stream.

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They didn't make a 2.8GHz 4K 21.5" iMac that year, only a 3.1GHz i5 and a 3.6GHz i7. "About this Mac" says 2.8GHz i5.


@markobrien - That not what I was saying. The issue is the part is not what you think.

iMac Intel 21.5" EMC 2889

iMac Intel 21.5" Retina 4K Display 2015

They look the same but have different logic boards and displays. Review the specs and the logic boards so you can see the displace connectors are different.


Then how do I find out what part it is or what part is the right part? As I said, I booted to an external monitor and "About This Mac" said "iMac (21.5-inch, Late 2015)," not "4K iMac," not "Retina iMac." Are you saying it's a 4K board but the firmware has been flashed to show the incorrect model and clock speed? How do I identify the correct board that I need to buy?


@markobrien - That tells us you got the regular retina system and now you need the regular logic board for it. Or.. replace the display with the 4K version the logic board is expecting and its cable.


@danj Okay, I will return the board and tell EveryMac their specs on the 2.8 are wrong. Thank you.


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Mark O’Brien sera éternellement reconnaissant.
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