Broadband (Cable, DSL, Satellite, Fiber Optics)/Memory cards replacing RAM modules.
Is it possible to replace RAM modules and cache memory with Memory cards in the motherboard?.
If not, Could there be advantages in motherboard Design changes implementation?.
Around 30 years ago when the IBM XT was released, memory was available on cards that would plug into the system bus. It was quickly discovered the extra overhead of bus negotiation and reduced speed of not having the memory directly addressable to the CPU was not worth any convenience factor.
Hopefully, this question is just to settle a bet with your buddies. If you are studying computer design, that is a different story - as if I were your instructor I would slap your hand with a ruler. The reason is that you clearly have not studied any industrial computer history. How can you hope to be any good as a computer hardware designer if you do not know about all the ideas that have been tried and abandoned in the computer business?
Computers today are built on a history of what has worked and what has not worked. Today they are the end products of what has worked. There is a reason memory is handled the way it is and you need to study older computer designs to understand why.