1. A method of clearing data in a memory of a computer system, the computer system comprising a processor, and a memory controller electrically connected to the processor and the memory for controlling accessing operations of the memory, the memory comprising a plurality of memory units, the method comprising: a) the processor generating a predetermined logic value, and delivering the predetermined logic value to the memory controller; and b) the memory controller repeatedly overwriting data stored in the plurality of memory units by the predetermined logic value.