Memory device communicating with a host at different speeds and managing access to shared memory

A memory device includes a high speed port, a low speed port, at least a first memory bank, a first register, and a multiplexer. The at least first memory bank is shared by the high speed port and the low speed port. The first register store information that indicates which one of the ports has permission to access the first memory bank. The multiplexer connects one of the high speed port or the low speed port to the first memory bank, in response to the information stored in the first register.