An operation method of a memory module which includes a plurality of memory devices (1220 - 1227), the method comprising: receiving a partial write command including a partial write enable signal and a plurality of mask signals, at a first time; during a strobe toggle interval after the first time, receiving a first data strobe signal toggling through a first data strobe line connected with a first memory device, among the plurality of memory devices, and receiving a second data strobe signal maintained at logic high through a second data strobe line connected with a second memory device, among the plurality of memory devices; receiving a plurality of data through a plurality of data lines, during a data input interval after the first time; and storing a part of the plurality of data in a plurality of memory cells (MG1 - MG31) included in the first memory device based on the plurality of mask signals, in response to the partial write enable signal. wherein: the plurality of mask signals include a first mask signal and a second mask signal, the first mask signal corresponds to first input data that is input during a first burst length and the second mask signal corresponds to second input data that is input during a second burst length, the storing of the part of the plurality of data in the plurality of memory cells included in the first memory device based on the plurality of mask signals, in response to the partial write enable signal, includes: when the first mask signal is in a disable state, storing a part of the first input data in the plurality of memory cells included in the first memory device; and when the second mask signal is in an enable state, not storing the second input data in the plurality of memory cells included in the first memory device. receiving a partial write command including a partial write enable signal and a plurality of mask signals, at a first time; during a strobe toggle interval after the first time, receiving a first data strobe signal toggling through a first data strobe line connected with a first memory device, among the plurality of memory devices, and receiving a second data strobe signal maintained at logic high through a second data strobe line connected with a second memory device, among the plurality of memory devices; receiving a plurality of data through a plurality of data lines, during a data input interval after the first time; and storing a part of the plurality of data in a plurality of memory cells (MG1 - MG31) included in the first memory device based on the plurality of mask signals, in response to the partial write enable signal. wherein: the plurality of mask signals include a first mask signal and a second mask signal, the first mask signal corresponds to first input data that is input during a first burst length and the second mask signal corresponds to second input data that is input during a second burst length, the storing of the part of the plurality of data in the plurality of memory cells included in the first memory device based on the plurality of mask signals, in response to the partial write enable signal, includes: the plurality of mask signals include a first mask signal and a second mask signal, the first mask signal corresponds to first input data that is input during a first burst length and the second mask signal corresponds to second input data that is input during a second burst length, the storing of the part of the plurality of data in the plurality of memory cells included in the first memory device based on the plurality of mask signals, in response to the partial write enable signal, includes: when the first mask signal is in a disable state, storing a part of the first input data in the plurality of memory cells included in the first memory device; and when the second mask signal is in an enable state, not storing the second input data in the plurality of memory cells included in the first memory device.