 However, Flash memory has been developed to become a widely used form of read-write mass storage with write speeds far exceeding competing technologies such as hard disk.The first regenerative capacitor memory built was the rotating capacitor drum memory of the Atanasoff–Berry Computer (1942).Each of its two drums stored thirty 50-bit binary numbers (1500 bits each), rotated at 60 rpm and was regenerated every rotation (1 Hz refresh rate).