2010 iMac GPU cross-compatibility

[MultiFinder17]

Random question for y'all. I've used a 2010 21" iMac (3.06 i3, 16GB, 256GB SSD, Radeon HD 4670) as my main desktop in my classroom for years now. This weekend, my old roommate gifted me his old 2010 27" iMac (2.93 i7, 16GB, 256GB SSD, Radeon HD 5750). I'd love to use this monster; the boost in CPU power and that monstrous screen would be lovely! However, I've been running Dosdude's Mojave patcher on the 21", as it has the only dedicated Radeon HD that actually works with Mojave and offers acceleration.

Would it be possible to gank the GPU from the 21" and swap it with that in the 27"? Are they compatible? I've read conflicting things about it. I'm very comfortable working inside the two machines (a computer just doesn't feel like it's mine until I've torn it down and rebuilt it, you know?). Any advice on the compatibility would be much appreciated!

 

[retta283]

From what I read elsewhere, if the 27" had the 5670, yes, but if 5750, no. However the connection is the same, and if you swap the heatsinks with it, maybe you can get it to fit properly, but there are differences in the size of the heatsink. I did hear a mention of 6970m as an upgrade path for 21.5" iMacs.

As far as I can tell, if you can make the 5750 fit in there physically, it will work. But I can't speak with certainty to the exact sizes of the boards

 

[MultiFinder17]

I’ll probably bring them both home this weekend to try out. Part of my problem is that I’ve found plenty of info about upgrading the GPU in the 21”, but next to nothing about downgrading the GPU in the 27” which is my primary goal here.

 

[mdgm]

Seeing this is a hardware question you might have more success in the iMac subforum: https://forums.macrumors.com/forums/imac.91/

There's a long thread on GPU upgrades in there though moving a stock GPU from one Mac to another isn't the same thing as putting one designed for newer Macs.