To suppress an electromagnetic interference noise radiated from a computer system by allowing a PCB(printed circuit board) to comprise an input/ output signal path, power source path, and ground path, which are surrounded with a ferrite attenuator.

A computer system 20 comprises a system core PCB 22 provided with a micro processor 24, and an input/output PCB 26 is connected to the system core PCB 22 with a connector 28 on the input/output PCB 26 and a corresponding connector 30 on the system core PCB 22. The input/output PCB 26 comprises an input/output signal path 42 which transfers an input/output signal between the connector 28 and the input/output PCB 26, a power-source path 44 which conveys a power to the input/output PCB 26 from the connector 28, and a ground path 46 which connects the input/output PCB 26 to a ground level, which are surrounded with a ferrite attenuator 50.