a substrate containing wiring traces for conducting signals;

a plurality of contact pads along a first edge of the substrate, the plurality of contact pads for mating with a memory module socket on a motherboard;

a branching Advanced Memory Buffer (AMB) mounted on the substrate for buffering host data;

uplink contact pads, in the plurality of contact pads, that carry southbound uplink frames of the host data generated by the host for writing to memory chips in downstream memory modules, and that carry northbound uplink frames of host data read from memory chips in downstream memory modules toward the host;

first downlink contact pads, in the plurality of contact pads, that carry first southbound downlink frames of the host data generated by the host for writing to a first plurality of memory chips in a first downstream memory module in a first branch, and that carry first northbound downlink frames of host data read from the first plurality of memory chips in the first downstream memory module in the first branch;

second downlink contact pads, in the plurality of contact pads, that carry second southbound downlink frames of the host data generated by the host for writing to a second plurality of memory chips in a second downstream memory module in a second branch, and that carry second northbound downlink frames of host data read from the second plurality of memory chips in the second downstream memory module in the second branch;

wherein the branching AMB connects through the wiring traces to the uplink contact pads, to the first downlink contact pads, and to the second downlink contact pads;

a replicator, in the branching AMB, for copying the southbound uplink frames received from the uplink contact pads to the first downlink contact pads to generate the first southbound downlink frames, and for copying the southbound uplink frames received from the uplink contact pads to the second downlink contact pads to generate the second southbound downlink frames; and

a northbound merger, in the branching AMB, for transferring the first northbound downlink frames received from the first downlink contact pads to the uplink contact pads to generate the northbound uplink frames, and for transferring the second northbound downlink frames received from the second downlink contact pads to the uplink contact pads to generate the northbound uplink frames,

whereby the branching fully-buffered memory-bus module replicates southbound uplink frames to generate both the first southbound downlink frames to the first branch of the first downstream memory module and the second southbound downlink frames to the second branch of the second downstream memory module.