Theoretically it MIGHT be possible but I think you would need to choose a CPU that was as close to the original Apple options as possible. Not only would you need a chip with the same socket, you’d need a chip with the same power requirements too.

Wether there would be a firmware conflict I couldn’t say - maybe some adventurous soul will let us know how they get on!

So I’ve been thinking of doing something with my old 27'“ imac from 2009 for a while now and so I’ve been trawling the forums looking for advice etc. Many of the comments here mirror my own thoughts on the matter - can I upgrade to a better CPU etc.

From what I’ve learned elsewhere it’s all dependent on what model of logic board is installed in your imac, namely do you have an EARLY 2009 imac with core 2 duo or do you have a later 2009 imac with ether i5 or i7 chips onboard?

If you in fact have the earlier model then you can only replace the chip with an identical one - i5 or i7 IS NOT AN OPTION.

Why? Because the board will not be able to supply the amount of power needed to run one of those i5 or i7 chips. If you want to upgrade to one of those chips then you are also going to need the appropriate logic board to run them.

This then leads us into the realm of conjecture: “I have a model with an i5 or i7 already onboard - can I upgrade it to a higher rated version?”