A memory module includes a first memory device, a second memory device, and a processing buffer circuit that is connected to the first memory device and the second memory device (independently of each other) and a host. A processing buffer circuit is provided, which includes a processing circuit and a buffer. The processing circuit processes at least one of data received from the host, data stored in the first memory device, or data stored in the second memory device based on a processing command received from the host. The buffer is configured to store data processed by the processing circuit. The processing buffer circuit is configured to communicate with the host in compliance with a DDR SDRAM standard.