1. A method of performing clear operations in a region having a subregion, comprising: responsive to a clear command: leaving a current clear count for the region unchanged; writing a predetermined value into each of the pixels of the subregion, but not into the pixels outside the subregion; and writing the current clear count into clear count storage locations corresponding to each of the pixels of the subregion, but not into clear count storage locations corresponding to the pixels outside the subregion.