A multi-die integrated circuit assembly includes an interposer substrate larger than the typical reticle size used in fabricating the “active area” in which the through-silicon vias (TSVs) and interconnect conductors are formed in the interposer. At the same time, each of the dies has its external power/ground and I/O signal line connections concentrated into a smaller area of the die. The dies are disposed or mounted on the interposer such that these smaller areas (with the power/ground/IO connections) overlap with the active area of the interposer. In this configuration, a plurality of dies having a combined area substantially greater than the active area of the interposer can be mounted on the interposer (and take advantage of the active area for interconnections).