Help with FAT16 and FAT32

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By sdsnatcher73

Prophet (3806)

sdsnatcher73's picture

07-12-2022, 11:50

Yes that is just due to cluster size. On FAT32 you will be able to have smaller clusters (possibly even 512 bytes in size). On FAT16 the number of total clusters is smallers zo clusters have to be bigger. Mostly 32Kbytes is used with FAT16. A 720kB file won’t be impacted as much as 100 7kB files (they will use 100 times 32kB so roughly 3.2MB).

By selios2000

Hero (561)

selios2000's picture

07-12-2022, 15:18

So when I format the SD card (2GB or 4GB) in FAT16 I must change the cluster size to less than 32KB? Or it will create some kind of problem to the SD (malfunctioning or files then not loaded correctly).

By ducasp

Hero (662)

ducasp's picture

07-12-2022, 16:13

selios2000 wrote:

So when I format the SD card (2GB or 4GB) in FAT16 I must change the cluster size to less than 32KB? Or it will create some kind of problem to the SD (malfunctioning or files then not loaded correctly).

You have 16 bits, so 64K Clusters... So that means 16KB for 1GB, 32KB for 2GB and 64KB for 4GB, you can't go lower.

So the larger the partition is, also larger is the space you lose (there is a term for that, slack space). If you are using 1 byte files, you would fill up the partition with 64K files, ocuppying 64KB and the rest is lost as slack space. If you are using only 100KB files you would be able to fill up the disk very close to its capacity... Yeah, fat 16 is a bitch for small files and "large" partitions, and fat 32 unfortunately is, not a reality for msx dos / nextor

By selios2000

Hero (561)

selios2000's picture

07-12-2022, 16:33

Thank you ducasp and the others, mystery is solved.

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