Assuming that computer has finitely many states to be in because of finiteness of its memory, we can model it as a very large deterministic finite automaton. Yo

Assuming that computer has finitely many states to be in because of finiteness of its memory, we can model it as a very large deterministic finite automaton. You cannot model a real computer as a LBA, because you don't necessarily have as many read-write memory as your input takes. If you think I'm wrong, please, tell me what makes you think that you can model real computers as LBAs.