An active matrix display device comprises a plurality of pixels, and driving circuitry arranged to drive each pixel with a pre-determined drive voltage level during a first phase (41) followed by an overdrive drive voltage level during a second phase (44). A partial frame store is for storing a fraction of the pixel data for the display. Input video data is written into the partial frame store (40) at a first rate and is read out of the partial frame store at a second rate which is greater than the first rate. The data read out of the partial frame store is processed for deriving the overdrive drive voltage level.