In 1976, IBM introduced the 500 KB Double Sided Single Density (DSSD) format, and in 1977 IBM introduced the 1–1.2 MB Double Sided Double Density (DSDD) format.
1976. aastal tutvustas IBM 500 kB Double Sided Single Density (DSSD) formaati ja 1977. aastal 1-1.2 MB Double Sided Double Density (DSDD) formaati.