RCS4864 wrote:
I have two older iMac 27' for 2013 and 2014 time frame. I'm slowly being bricked out because of the limited IOS support available. Can I upgrade the RAMM, processor or main board on these to support later IOS versions?
I think doing RAM hardware upgrades on Macs that are 10+ years old is a waste of time and money. The processor and motherboard cannot be upgraded, as others have explained. The hardware is no doubt wearing out as well anyway.
The 2014 model can run Big Sur and from my own experience with an old 2013 MacBook Air, one can still do lots of things with Big Sur. It has a recent version of Office 365 (but cannot be upgraded to the latest version; still, it works fine), can run recent (but not the latest) versions of Adobe apps, and most web sites work fine and for those that might not, using Chrome or Firefox still works fine. I would guess these older computers with Big Sur will start to become less useful as time goes by and within about two years, will have too many limitations to be useful.
As an example, the 2023 version of TurboTax required Monterey to even run, so Big Sur was just too old.
Your 2013 iMac might be stuck on Catalina and that one I would retire, it's just too old with too many limitations (my opinion based on my 2010 MacBook Air which runs High Sierra and 2013 MacBook Air which runs Big Sur).
The old Macs I still have (2015 iMac, 2013 Macbook Air, and 2010 MacBook Air) I keep mostly for fun like one keeps old things in a museum or maybe old cars that one tries to keep running, I use newer Macs on the latest version of Sonoma for anything that really matters.
You can get a brand new Mac for under $1000, although I would recommend adding some capability to those lowest cost models to make them more useful, so in practice a new one would likely cost a bit more. You can also get fairly recent models of refurbished Macs with warranties from Apple and from a few reliable companies like OWC/Macsales.