Boot Sector
Offset |
Size |
Description |
Comments |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0 (0x00) |
3 |
JumpBoot |
0xEB7690 |
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3 (0x03) |
8 |
FileSystemName |
"EXFAT> |
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11 (0x0B) |
53 |
MustBeZero |
|
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64 (0x40) |
8 |
PartitionOffset |
In sectors; if 0, shall be ignored |
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72 (0x48) |
8 |
VolumeLength |
Size of exFAT volume in sectors |
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80 (0x50) |
4 |
FatOffset |
In sectors |
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84 (0x54) |
4 |
FatLength |
In sectors. May exceed the required space in order to align the second FAT |
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88 (0x58) |
4 |
ClusterHeapOffset |
In sectors |
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92 (0x5C) |
4 |
ClusterCount |
2^32-11 is the maximum number of clusters could be described |
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96 (0x60) |
4 |
RootDirectoryCluster |
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100 (0x64) |
4 |
VolumeSerialNumber |
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104 (0x68) |
2 |
FileSystemRevision |
as MAJOR.minor, major revision is high byte, minor is low byte; currently 01.00 |
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106 (0x6A) |
2 |
VolumeFlags * ↓ |
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108 (0x6C) |
1 |
BytesPerSectorShift |
Power of 2. Minimum 9 (512 bytes per sector), maximum 12 (4096 bytes per sector) |
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| 109 (0x6D) | 1 | SectorsPerCluster Shift |
Power of 2. Minimum 0 (1 sector per cluster), maximum 25 – BytesPerSectorShift, so max cluster size is 32 MB |
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110 (0x6E) |
1 |
NumberOfFats |
2 is for TexFAT only |
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| 111 (0x6F) | 1 | DriveSelect |
Extended INT 13h drive number; typically 0x80 |
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112 (0x70) |
1 |
PercentInUse |
0..100 – percentage of allocated clusters rounded down to the integer 0xFF – percentage is not available |
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| 113 (0x71) | 7 | Reserved |
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120 (0x78) |
390 |
BootCode |
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| 510 (0x1FE) | 2 | BootSignature |
0xAA55 |
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512 (0x200) |
2^BytesPerSectorShift - 512 |
ExcessSpace |
Not used |
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