Chosen Solution
So apparently I can upgrade the CPU to 4.0GHz quad-core Intel Core i7 but I am new to all of this and have no idea where to buy it. Which one is compatible with my computer and from which reputable, trusted store? iMac (Retina 5K, 27-inch, Late 2015)
Take a serious look at the guides before you even try. This isn’t like a PC where it doesn’t involve major surgery and you can revert back without a major disassembly plus information is easier to come by - even if it’s official validation data provided by support in a forum. The job is a total PITA on the iMac and Apple isn’t open about it and actively goes out of their way to hide it. This guide should give you a good idea of what you’re about to attempt - make your judgements carefully since any system damage will be $$$ expensive to correct. It’s doable, but can only be pushed up to a 6700K, which may not be enough of an improvement to justify the significantly more difficult install. Compare it to your current CPU before buying anything. Your money will be better spent on RAM and an SSD. Most people get a system with a CPU that performs so closely to the original it’s not worth risking needing an expensive motherboard to gain a marginal speed bump. It only ever makes sense if you got a i3 one and are willing to go all in and max the CPU out.
