Generally, a method and apparatus for electro-chemical polishing a metal layer disposed on a substrate is provided. A computing device includes a display and a mechanism. One or more components of the spherical mechanical linkage may be symmetric about an axis. 0 minutes respectively, with said fractions used both individually, and in combination. A control circuit 22 controls so as to provide a voltage polarity of the final line in the periodicity of every four scanning lines to a signal line prior to driving a signal line corresponding to the first scanning line Y at the beginning of a frame.