A memory system includes a high-bandwidth memory device, the high-bandwidth memory device having a relatively high operation bandwidth, the high-bandwidth memory device having a plurality of access channels. A low-bandwidth memory device has a relatively low operation bandwidth relative to the high-bandwidth memory device, the low-bandwidth memory device having one or more access channels. An interleaving unit performs a memory interleave operation among the plurality of access channels of the high-bandwidth memory device and an access channel of the one or more access channels of the low-bandwidth memory device.