An apparatus includes a first die having a first bus, a second die having a second bus stacked on the first die, a plurality of through silicon vias connecting the first bus to the second bus, and first control logic for sending data to identified ones of the plurality of through silicon vias. Also, optionally, second control logic for determining a first set of the plurality of through silicon vias that are nonfunctional, wherein the second control logic is configured to send information to the first control logic identifying the first set of the plurality of through silicon vias or identifying a second set of through silicon vias that are functional. Also a method of sending signals through a plurality of through silicon vias.