FATX is based on FAT16 and FAT32, the basic differences being that many legacy fields have been dropped from the FAT table.

FATX comes in two varieties: FATX16 and FATX32

Bytes per sector

Supported on all FATs, Always 512 bytes on FATX

Reserved clusters

Supported on all all FATs, FATX has no reserved clusters

Number of root directory entries

Supported on all FATs, FATX has a constant value of 256 (one cluster)

Number of sectors

Supported on all FATs, now Redundant and definied by partitioning

Media code

Supported on all FATs, is now Legacy

Number of sectors the FAT occupies

Supported on all FATs, Now Redundant, and can be calculated with volume size

Sectors per track

Supported on all FATs, is now Legacy

Heads

Supported on all FATs, is now Legacy

Flags ("Fat Mirroring", "Active FAT")

Supported on FAT32 only, Not supported on FATX

Filesystem version

Supported on FAT32 only, But There will never be more than one version of FATX.

First cluster in root directory

Supported on FAT32 only, Uncertain about inclusion in FATX

Filesystem info sector

Supported on FAT32 only, Not supported on FATX

Backup boot sector

Supported on FAT32 only, Not supported on FATX