Extended BPB for Device

The physical device driver maintains two BPBs for each drive. One is the current BPB that corresponds to the media in the drive. The other is a recommended BPB based on the type of media that corresponds to the physical device. (For example, for a high-density drive, the BPB is for a 96 tracks-per-inch (TPI); for a low-density drive, the BPB is for a 48 TPI). The low bit of the Command Information field indicates which BPB the application needs to see.