Assignment of select I/O objects to banks with mixed capacities using integer linear programming

A method of assigning input/output (I/O) objects of a circuit design to banks of a target device using integer linear programming can include assigning the I/O objects of the circuit design to I/O groups according to compatibility among the I/O objects, and establishing a plurality of relationships, comprising measures of bank capacity, regulating assignment of the I/O objects of I/O groups to banks of the target device. Each measure of bank capacity can indicate a maximum number of I/O objects from a selected I/O group that can be assigned to a selected bank of the target device. The method also can include determining whether a feasible solution exists for assignment of the I/O objects of the circuit design to banks of the target device by minimizing an object function while observing the plurality of relationships.