A memory controller, a PCB and a computer system employing the memory controller, and a memory adjusting method using the memory controller. The memory controller interfaces data reading from and writing to a memory and includes: a characteristic estimating part estimating a characteristic of a memory output signal outputted from the memory for the data reading and writing; and a characteristic adjusting part controlling the memory so that the characteristic of the memory output signal is within a predetermined reference range if the characteristic of the memory output signal estimated by the characteristic estimating part is beyond the predetermined reference range.