An apparatus comprising: dice arranged in a stack, the dice including a first die and a second die; connections configured to provide communication among the dice, at least a portion of the connections going through at least one of the dice, wherein the connections include a first portion, a second portion, a third portion, and an additional portion, the first portion, the second portion, the third portion, and the additional portion are located at the first die, the connections further include a first additional portion, a second additional portion, and a third additional portion, and the first additional portion, the second additional portion, and the third additional portion are located at the second die; the apparatus being configured to replace the first portion of the connections with the third portion of the connections if the first portion is defective; and a module configured to receive information including a first input bit from a the first portion of the connections, a second input bit from the second portion of the connections, and a third input bit from the third portion of the connections, wherein the module is configured to shift the first input bit from the first portion to the additional portion, to shift the second input bit from the second portion to the additional portion, and to shift the third input bit from the third portion to the additional portion, the module configured to provide the first, second, and third input bits to the first portion, second portion, third portion, respectively, through the first additional portion, the second additional portion, and the third additional portion, respectively, the module is configured to obtain a first output bit (D1 OUT) from the additional portion, to obtain a second output bit (D2 OUT) from the additional portion, and to obtain a third output bit (D3 OUT) from the additional portion, the first output bit being based on the first input bit, the second output bit being based on the second input bit, and the third output bit being based on the third input bit, the module is configured to compare the value of the first input bit with the value of the first output bit (D1 OUT) to check for defects in the connections, the module is configured to compare the value of the second input bit with the value of the second output bit (D2 OUT) to check for defects in the connections, and the module is configured to compare the value of the third input bit with the value of the third output bit (D3 OUT) to check for defects in the connections. dice arranged in a stack, the dice including a first die and a second die; connections configured to provide communication among the dice, at least a portion of the connections going through at least one of the dice, wherein the connections include a first portion, a second portion, a third portion, and an additional portion, the first portion, the second portion, the third portion, and the additional portion are located at the first die, the connections further include a first additional portion, a second additional portion, and a third additional portion, and the first additional portion, the second additional portion, and the third additional portion are located at the second die; the apparatus being configured to replace the first portion of the connections with the third portion of the connections if the first portion is defective; and a module configured to receive information including a first input bit from a the first portion of the connections, a second input bit from the second portion of the connections, and a third input bit from the third portion of the connections, wherein the module is configured to shift the first input bit from the first portion to the additional portion, to shift the second input bit from the second portion to the additional portion, and to shift the third input bit from the third portion to the additional portion, the module configured to provide the first, second, and third input bits to the first portion, second portion, third portion, respectively, through the first additional portion, the second additional portion, and the third additional portion, respectively, the module is configured to obtain a first output bit (D1 OUT) from the additional portion, to obtain a second output bit (D2 OUT) from the additional portion, and to obtain a third output bit (D3 OUT) from the additional portion, the first output bit being based on the first input bit, the second output bit being based on the second input bit, and the third output bit being based on the third input bit, the module is configured to compare the value of the first input bit with the value of the first output bit (D1 OUT) to check for defects in the connections, the module is configured to compare the value of the second input bit with the value of the second output bit (D2 OUT) to check for defects in the connections, and the module is configured to compare the value of the third input bit with the value of the third output bit (D3 OUT) to check for defects in the connections.