A reconfigurable high performance computer occupies less than 360 cubic inches and has an approximate compute power of 0.7 teraflops per second while consuming less than 1000 watts. The computer includes a novel stack of semiconductor substrate assemblies. Some semiconductor substrate assemblies involve field programmable gate array (FPGA) dice that are directly surface mounted, as bare die, to a semiconductor substrate. Other semiconductor substrate assemblies of the stack involve bare memory integrated circuit dice that are directly surface mounted to a semiconductor substrate. Elastomeric connectors interconnect adjacent semiconductor substrates proceeding down the stack. Tines of novel comb-shaped power bus bar assembly structures extend into the stack to supply DC supply voltages. The supply voltages are supplied from bus bars, through vias in the semiconductor substrates, and to the integrated circuits on the other side of the substrates. The power bus bars also serve as capacitors and guides for liquid coolant.