A method of input/output (I/O) block placement assigned to an input/output bank includes formulating a placement algorithm using integer linear programming (ILP) and simultaneously placing single groups and Relatively Placed Module (RPM) groups of I/O blocks in the I/O bank. The method further includes determining a placeability matrix P and a binary assignment matrix X used for the ILP. The method can further eliminate all assignment matrix elements of X equal to 0 in the integer linear programming and re-index any remaining elements. The method can further place all I/O blocks according to a solution if solving of the standard ILP formulation results in a feasible solution. Optionally, the method generates a placement solution that is as close as possible to an external reference solution specified by designer. Optionally, the method analyzes which constraints were violated and generates useful error information.