A memory access technology and a computer system, where the computer system includes a memory controller and a medium controller connected to the memory controller. In the computer system, when detecting that an error occurs in first data that is returned by the medium controller in response to a first send command, the memory controller determines sequence information of the first send command in a plurality of send commands that have been sent by the memory controller within a time period from a time point at which the first send command is sent to a current time, and sends a data retransmission command to the medium controller to instruct the medium controller to resend the first data based on the sequence information.