A memory system includes a memory controller, a first memory module and second through k-th memory modules. The first memory module is directly coupled to the memory controller without any other memory modules communicatively coupled therebetween, through a first memory bus, and the first memory module exchanges first data with the memory controller. The second through k-th memory modules are coupled to the first memory module with a multi-drop connection through a second memory bus and the second through k-th memory modules exchange second data with the memory controller via the first memory module.