A method includes steps of: assigning a value of a setting variable to a memory allocation variable; allocating address space to peripheral devices based on the memory allocation variable; determining whether allocated address space is sufficient; acquiring a system-wise greatest demand size value when allotted address space is insufficient; determining whether the memory allocation variable exceeds the system-wise greatest demand size value; updating the memory allocation variable to have a larger value when the memory allocation variable does not exceed the system-wise greatest demand size value; and assigning the value of the memory allocation variable to the setting variable when the memory allocation variable exceeds the system-wise greatest demand size value.