1. A method for video processing using a reference frame of video data in an external memory, said method including the steps of: (a) pre-caching in an internal memory a sequence of partial frames of the reference frame, including by predetermining each of the partial frames in a manner independent of which reference data, if any, of the reference frame is actually requested for use in performing video processing; and (b) while one of the partial frames remains cached in the internal memory, asserting at least one request for reference data from the reference frame, and responding to the request including by determining whether at least some of the reference data indicated by said request is cached in the internal memory.