A structure comprises a first die, a second die, an interposer, a third die, and a fourth die. The first die and the second die each have a first surface and a second surface. First conductive connectors are coupled to the first surfaces of the first and second dies, and second conductive connectors are coupled to the second surfaces of the first and second dies. The interposer is over the first and second dies. A first surface of the interposer is coupled to the first conductive connectors, and a second surface of the interposer is coupled to third conductive connectors. The third and fourth dies are over the interposer and are coupled to the third conductive connectors. The first die is communicatively coupled to the second die through the interposer, and/or the third die is communicatively coupled to the fourth die through the interposer.