Sectors Per Track

SPT is the number of sectors that a hard drive has on each of its track.

On modern hard disk drives (IDE and SCSI) this number is a “false” value since the hard drive uses a feature called geometry translation. The hard disk geometry (its number of cylinders, sides and sectors per track) is only used to calculate its total capacity (the total number of sector it has). In reality the hard drive doesn’t have the number of cylinders, sides and tracks stated on its geometry.

Hard disk drives use a scheme called Zone Bit Recording (ZBR) where the outer cylinders have more sectors than the inner ones due to the obvious difference in available physical space. So when a hard drive says it has 63 sectors per track this is a false number, since the number of sectors per track varies depending on the track position.