To be honest, the case is still the original one, but almost every other part has since been replaced. Now, I’ve taken it back to the shop where I bought it 20 years ago and asked them to upgrade the motherboard, CPU, and memory - the last of the original parts.
So, is it still the same computer?
I also like that I can just keep replacing parts on an existing product rather than buying an entirely new device each time. That’s exceedingly rare feature these days.
If you kept the same case, I’d call it the same computer.
It’s like a car: if you replace the seat covers, add a new air freshener, and replace the transmission, well, it’s still the same car because the outside shell didn’t change, just the bits inside it.
Ok but if you break the front and back faces of your phone then send it in to get them replaced, is it still the same phone?
I think what changes the identity of something is changing it’s “brain”, or how it operates. In the case of phones/computers, changing the CPU to a better one would change it’s performance, so it would be a new thing. Same as with a car engine. If you have a 4-banger and change it to a V6 or even replacing it with a newer engine, it’s now another car even if it’s appearance is the same.
To me, it’s a percentage game. OP’s computer is now 90% a different computer, your phone example is 20% a different phone, and your car is 30% a different car. The Ship of Theseus is 100% a different ship when it is fully swapped out, no matter how long it took.