Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, are described for performing asymmetric data communication at a host-device interface of a system. The methods include identifying devices coupled to a host of the system and generating a system topology that identifies a connectivity of the devices and identifies bus lanes that enable data transfers at the system. The host determines that a first connection between the host and a first device of the multiple devices has an asymmetric bandwidth requirement. The host configures a set of bus lanes of a data bus connecting the first device and the host to allocate a different number of the bus lanes to data egress from the host than to data ingress to the host. The bus lanes are configured to allocate the differing number of bus lanes based on the asymmetric bandwidth requirement of the first connection.