An overdrive engine generates output frames to be used to drive a display from input frames to be displayed. Each output frame is generated on a region by region basis from the corresponding regions of the input frames. If it is determined that an input frame region has changed significantly since the previous version(s) of the input frame, an overdriven version of the input frame region is generated for use as the corresponding region in the output frame. On the other hand, if it is determined that the input frame region has not changed since the previous version of the input frame, then the new input frame region is used without performing any form of overdrive process on it for the corresponding region in the output frame.