Patent ID: 6965967

Claim:
A data prereading device comprising: a command history information storage unit operable to hold historic information of read commands which are received from a host device as information for reading data recorded on a disk memory medium; a continuity detection unit operable to detect a direction along which prereading of data is to be performed based on the read commands held in said command history information storage unit; a prereading area decision unit operable to decide the position and size of data on the disk memory medium to be preread based on the read commands held in said command history information storage unit and the data prereading direction detected by said continuity detection unit; a cache memory operable to hold preread data; a prereading startup unit operable to read, from the disk memory medium, the data to be preread which said prereading area decision unit decided is to be preread, and to store the preread data in said cache memory; a cache memory pointer holding unit operable to hold an under-transfer address indicating the position, on said cache memory, of data which is currently being transferred to the host device, and a next preread data storage start address indicating the position on the cache memory where next preread data is to be stored; and a prereading startup judgement unit operable to judge whether or not prereading of data is to be performed so as to leave at least several blocks of data which have already been transferred to the host device on the cache memory by employing the under-transfer address and the next preread data storage start address held by said cache memory pointer holding unit.