I apologize for this question and I don’t mean to be rude: but are you actually a programmer? You have stated elsewhere that your field is economics and what you wrote here is factually wrong, so I’m wondering if you’re mistaken because it’s not your field or not expressing yourself in a way I can understand.
Just to be clear, old PCs like 386, 486, Pentium and P6 cannot handle the amount of memory we have today because they have a 32-bit address bus (or 36-bit in case of P6, but the linear address space was still limited to 32 bits). And there is a whole myriad of reasons why you can’t put older CPUs in modern motherboards, that have nothing to do with “processing power” needed to index, store, retrieve and keep the integrity of the data.