System for controlling storage device for storing data at second density that is not integral multiple of first density by varying the device motor speed

An apparatus for controlling a peripheral storage device of a data processing system, wherein said peripheral storage device includes a motor and is designed to store data at a first density and integral multiples thereof in response to receiving a plurality of control signals while said motor operates at a predetermined rotation speed, said system comprising:

• means for transmitting a particular control signal among said plurality of control signals from said data processing system to said peripheral storage device to initiate an operation other than storing data;
• means for transmitting a status signal to said data processing system to indicate that said peripheral storage device is performing said operation other than storing data in response to receiving said particular control signal;
• means for varying said particular control signal;
• and
• means for varying said rotation speed of said motor and storing data within said peripheral storage device at a second density that is not an integral multiple of said first density in response to varying said particular control signal.