A package substrate for connecting together semiconductor devices with other semiconductor device packages. The package substrate includes an exposed core layer with at least one via exposing a conductive layer of the package substrate. A first portion of the package substrate may include a solder mask on top and bottom surfaces. A first semiconductor device may be connected to the first portion of the package substrate. Layers of a second portion of the package substrate are removed to expose a core layer and vias are created in the exposed core layer to expose the conductive layer. Conducive material at least partially filling the vias may be used to connect a semiconductor device package to the second portion of the package substrate. The semiconductor device packages may communicate through conductive layers in the package substrate. The package substrate may be used to connect the semiconductor packages to a motherboard.