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HP 50g & SD Cards: Performance, Format, Notes
07-21-2016, 10:34 AM (This post was last modified: 07-22-2016 08:33 AM by matthiaspaul.)
Post: #26
RE: HP 50g & SD Cards: Performance, Format, Notes
(07-20-2016 04:53 PM)Joe Horn Wrote:  Sorry about the format ambiguity; all I know for sure is that Win7 says that these cards are formatted as "FAT". I'm guessing that means FAT16?
Basically yes. It actually means: FAT12, FAT16, FAT16B or FAT16X depending on the volume's size and several other conditions. Since FAT12 and the original FAT16 format are only used on very small media (typically smaller 32 MB), it means FAT16B or FAT16X in practise today. FAT16X is only used if LBA-access is mandantory. As this isn't necessary for media sizes of 2 GB, the calculator (and Windows) will use FAT16B normally.

From the file system's perspective, there is no difference between FAT16, FAT16B and FAT16X, they all use 16-bit clusters. FAT16 uses an old-style BPB with 16-bit sector entries and on partitioned media it uses partition type 4, whereas FAT16B uses a "new"-style BPB with 32-bit sector entries (and partition type 6). FAT16X is almost like FAT16B except for that some of the BPB entries are not used and that it uses partition type Eh to enfore LBA-access. Except for when it is important to distinguish between these types, all these variants are called "FAT16" in practise.

When Windows mentions "FAT32", it is either FAT32 or FAT32X. (Windows does not support FAT32+ and FAT32B.) The difference between FAT32 and FAT32X is that some of the BPB entries are not used on FAT32X, and on partitioned media FAT32 uses partition type Bh, whereas FAT32X uses Ch to enfore LBA-access. Except for when it is important to distinguish between FAT32 and FAT32X, they are both called "FAT32" in practise.

Greetings,

Matthias


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RE: HP 50g & SD Cards: Performance, Format, Notes - matthiaspaul - 07-21-2016 10:34 AM



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