PC Hardware in a Nutshell, 3rd Edition

FAT32

The hard limit of 2 GB on FAT16 volume size and the huge waste on large volumes led Microsoft to introduce the FAT32 filesystem with Windows 95 OSR2. Microsoft really should have called it FAT28 because four of the 32 address bits are reserved. Using 28-bit addressing, FAT32 addresses up to 268,435,456 sectors or clusters. Addressing individual sectors, FAT32 can access (268,435,456 sectors × 512 bytes/sector = 137,438,953,472 bytes), or 128 GB. In fact, though, FAT32 does not use individual sector addressing, simply because the overhead involved in managing so many small disk space allocation units would significantly degrade performance. Instead, FAT32 continues to use cluster-based addressing, but with much smaller cluster sizes than FAT16. Table 14-2 lists the cluster sizes that FAT32 uses for various partition sizes.

Table 14-2. The relationship of FAT32 partition size to cluster size

Partition size	Sectors / Cluster	Cluster size
< 256 MB	1	512 bytes
256 MB - 8 GB	8	4 KB
8 GB - 16 GB	16	8 KB
16 GB - 32 GB	32	16 KB
> 32 GB	64	32 KB

The smallest FAT32 partition you can create with the fdisk and format utilities is 512MB, unless you use undocumented command-line switches, which are undocumented for good reasons. You can convert FAT16 volumes smaller than 512 MB to FAT32 by using the Windows 98 conversion utility or PartitionMagic, but there is little reason to do so because FAT32 benefits only large volumes.

FAT32 also eliminates the limitation on root directory ...