A chip system includes a first chip, a first DRAM, a second chip and a second DRAM. The first chip includes a first DRAM controller and a first serial transmission interface. The first DRAM is coupled to the first DRAM controller. The second chip includes a second DTAM controller and a second serial transmission interface. The second serial transmission interface is coupled to the first serial transmission interface. The second DRAM is coupled to the second DRAM controller. When the first chip intends to store first data and second data, the first chip stores the first data into the first DRAM via the first DRAM controller, and transmits the second data to the second chip via the first serial transmission interface; and the second chip stores the second data into the second DRAM via the second DRAM controller.