Semiconductor disk device having a large capacity of quick-access memory

Abstract

A semiconductor disk device for storing or outputting data in accordance with a write request from an outer unit or a read request comprising a volatile memory for writing input data from the outer unit and for storing data to be read in the outer unit, a battery for supplying power to the semiconductor disk device when a power supply of the semiconductor disk device is interrupted, a nonvolatile storage outputting initially stored data to the volatile memory when the power supply is input, and operating with power supplied from the battery when the power supply is interrupted, thereby storing data stored in the volatile memory to save the stored data, a detecting section for detecting whether or not the battery can supply power, and a write-through setting section for changing a write-path of the input data from the outer unit to a write-through path where the input data is written onto not only the volatile memory but also the nonvolatile storage means when it is detected by the detecting means that the battery cannot supply power.