Can you swap a late 2015 i5 logic board with late 2015 i7 board?

My goal isn’t to swap CPUs. I’m looking to replace the logic board because I believe I have a bad GPU. Problem is I can’t find my exact logic board. But from what you said sounds like I COULD do the swap. What about the retina differences?

Problem is I can’t find my exact logic board. But from what you said sounds like I COULD do the swap.

@tsparacino - What does the onboard diagnostic LED’s telling you?

What is the symptoms you are encountering so we have a better idea on what is the best course of action. I would hate to have you go with great expense only to discover that was not the issue.

Basically, the computer was running insanely slow… Very unresponsive to input. Similar to a bad hard drive. Apple kept it for several days and said they ran every test they could, and all hardware checked out, but they suspected it was a display issue and could be the GPU. They said it would likely cost 600 bucks so I decided to look on my own.

When boot in safe mode, everything runs smooth and snappy… in normal boot, it takes a several seconds for my password to even appear after typing it in. Dialog boxes and windows often display ghosting for about 10 seconds as well.

Not a software issue, because I have erased, reinstalled, erased, reinstalled, probably 10 times.

Found a logic board for $70 so I figured that would be a good try however it doesn't have the PCI slot which I need so the search continued.

Sorry, that was so lengthy, thanks for the help Dan!

Well, you don’t need a new logic board, so let’s focus on on what is the most likely issue, that’s your drive setup! Fusion Drives are the devil, as they have two sides the slower spinning HDD and the faster but more expensive (at the time) SSD. The way these drives wear and how Apple used them only work so long and slowly fail, you’ve noted the system gets slower and slower.

So I would recommend replacing the HDD element to a 2.5” SATA SSD and removing the Fusion drive caching SSD blade SSD as being the easiest fix.

iMac Intel 21.5" (Late 2012-2019) SSD Upgrade Kit and here’s the guide iMac Intel 21.5" EMC 2889 Hard Drive Replacement sadly you will still need to pull the other SSD as it will mess you up iMac Intel 21.5" EMC 2889 Blade SSD Replacement you could also replace it with a bigger SSD and after backing up your data wipe down the HDD reuse it for an external drive using the case.

Interesting… I did install a new logic board and there are other issues with apps not working but the previous problem with unresponsiveness is gone. I will say that due to the new board lacking the PCIe slot the SSD blade is gone so I’m just operating on my old hard drive (no fusion). Sounds like possibly I could diagnose further by putting my old board back in, minus the SSD blade. If the problem is in that SSD blade I should see an improvement. That’s what I’m gathering from your description anyway. Trying to keep costs minimal for now as I’ll likely replace it in a year or so.