don't use BPB_TotSec16 to determine FAT type#547
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Description for BPB_TotSec16: > This field is the old 16-bit total count of sectors on the volume. > This count includes the count of all sectors in all four regions of > the volume. This field can be 0; if it is 0, then BPB_TotSec32 must > be non-zero. For FAT32 volumes, this field must be 0. For FAT12 and > FAT16 volumes, this field contains the sector count, and BPB_TotSec32 > is 0 if the total sector count “fits” (is less than 0x10000). Source: https://download.microsoft.com/download/1/6/1/161ba512-40e2-4cc9-843a-923143f3456c/fatgen103.doc TL;DR: BPB_TotSec16 can be zero even for FAT12/FAT16 volumes if the sector count exceeds 0x10000. Instead, let's use BPB_FATSz16. Unlike BPB_TotSec16, BPB_FATSz16 must be non-zero for FAT12/FAT16 volumes because BPB_FATSz32 only exists in the FAT32 BPB. According to the document mentioned above, BPB_FATSz16 must be zero for FAT32 volumes.
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@NikoPit Please give this a try and report back to us if this solves your issue. |
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lemme try it |
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and btw how long does it take for you guys to load a ramdisk, it takes like 1 minute to load a 16mb ram disk. is this normal? |
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Yeah, I noticed it's kinda slow though I also didn't use hardware acceleration to run the VM. Are you using hardware accelerated virtualization? |
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nope im not using kvm |
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Ok. Does this PR resolve your issue? |
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yup! this fixed the issue |
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please check #549 as well! |
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Description for BPB_TotSec16:
Source: https://download.microsoft.com/download/1/6/1/161ba512-40e2-4cc9-843a-923143f3456c/fatgen103.doc
TL;DR: BPB_TotSec16 can be zero even for FAT12/FAT16 volumes if the sector count exceeds 0x10000.
Instead, let's use BPB_FATSz16. Unlike BPB_TotSec16, BPB_FATSz16 must be non-zero for FAT12/FAT16 volumes because BPB_FATSz32 only exists in the FAT32 BPB. According to the document mentioned above, BPB_FATSz16 must be zero for FAT32 volumes.
Closes #546