In 2010 hard disk manufacturers defined the Advanced Format (AF).
AF disks have a larger internal (physical) sector size of 4096 bytes (4K) instead of
512 bytes as previously.
To ensure backward compatibility with existing operating systems the access to many AF disks used a (logical) sector size of 512 bytes.
Meanwhile AF disks exist which can be accessed only with a sector size of 4096 bytes.
Consequently there are the following disk variants:
- 512n: the internal sector size is 512 bytes and the access occurs also with a sector size of 512 bytes
- 512e: the internal sector size is 4096 bytes but the access occurs still with a sector size of 512 bytes
- 4Kn: the internal sector size is 4096 bytes and the access occurs also with a sector size of 4096 bytes
For application programs there is no difference between 512n and 512e disks. Both are accessed with 512 byte sectors.
The internal organisation of the data storage is not relevant for the application program.
A differentiation is helpful only for performance reasons to optimise the access strategy.
On the other hand 4Kn disks require support in the application program, since the program must use a different sector size of 4096 bytes for accessing the disk.
In Boot-US 4Kn disks are marked by the suffix (4Kn), see the following screenshot.