A method comprises connecting a substrate having a plurality of integrated circuit (IC) dies to a package substrate, so that the package substrate extends beyond at least two edges of the substrate, leaving first and second edge portions of the package substrate having exposed contacts. The first and second edge portions meet at a first corner of the package substrate. At least a first upper die package is placed over the substrate, so that first and second edge portions of the first upper die package extend beyond the at least two edges of the substrate. Pads on the first and second edge portions of the first upper die package are connected to the contacts of the first and second edge portions of the package substrate.