A memory module supports multiple memory channel modes, each including a double-date-rate (DDR) data channel supported by an independent command-and-address (CA) channel. In a two-channel mode, the memory module supports two DDR data channels using two respective DDR CA channels. Each CA channel includes a corresponding set of CA links. In a four-channel mode, the memory module supports two pairs of DDR data channels, each pair supported by a pair of independent CA channels. Memory commands issued in the four-channel mode are time interleaved to share one of the sets of CA links.