Information processing apparatus and control method for storing multi-bit data with changeable variation width

An information processing apparatus comprising:

• a solid state drive (SSD) configured with a multi-bit cell for storing multi-bit data in one memory cell and configured to include an electrically rewritable non-volatile storage unit;
• and
• a main control unit configured to execute processing based on data stored in the SSD, wherein
• the SSD includes a storage control unit configured to control access to the non-volatile storage unit, and configured to execute a storage process through which a variation width of a threshold voltage is changeable when the multi-bit data is stored in the multi-bit cell, and
• the storage control unit is configured to store the multi-bit data such that the variation width of the threshold voltage is narrower for a specific area, which is set by the main control unit, than for other areas, among storage areas of the non-volatile storage unit
• the SSD includes a position information storage unit configured to store logical position information on the specific area in the non-volatile storage unit,
• the storage control unit is configured to determine, when data is stored in a designated logical position that is a logical position designated by the main control unit, whether or not the designated logical position is the specific area based on the logical position information stored in the position information storage unit and store, when the designated logical position is the specific area, the data in the designated logical position with a high-quality storage mode in which the variation width of the threshold voltage is narrower than in a normal storage mode, and
• the storage control unit is configured to execute, in the high-quality storage mode,
• an application process of applying a voltage for storing the data to the multi-bit cell for a predetermined period obtained by dividing an application period,
• a checking process of checking whether or not the threshold voltage falls within the variation width of the threshold voltage, after the application process is performed, and
• a repeating process of repeating the application process and the checking process until the threshold voltage falls within the variation width of the threshold voltage.