A semiconductor chip is provided which includes active and inactive IP cores. The main pole forming method includes etching an exposed side face of a main pole layer, and the plated foundation film, thereby defining a recording track width. When the link copy mode is set in the master machine and when the user tries to select an operation mode which can not be executed in the master and slave machines concurrently, then copying is prohibited. A plurality of stretchers each have a stretcher end pivotally connected to an intermediate portion of an associated rib and a runner end pivotally connected to the runner.