Double side mounted package structures and memory modules incorporating such double side mounted package structures are described in which memory packages are mounted on both sides of a module substrate. A routing substrate is mounted to a bottom side of the module substrate to provide general purpose in/out routing and power routing, while signal routing from the logic die to double side mounted memory packages is provided in the module routing. In an embodiment, module substrate is a coreless module substrate and may be thinner than the routing substrate.