A method is provided and includes several operations: forming a first group of macros in a first region, wherein the first group of macros are aligned with a first boundary of a channel that is coupled thereto through pins of the first group of macros; forming a second group of macros in the first region to align with a second boundary of the channel that is coupled thereto through pins of the second group of macros, wherein the first and second groups of macros are coupled to a first register; and forming a third group of macros in a second region different from the first region. A first macro and a second macro that are in the third group of macros are aligned with the first and second boundaries respectively. The third group of macros are coupled to a second register different from the first register.