MR> The problem is that I'm not certain how to handle drives larger than
 MR> 4GB. The freespace bitmap list is four sectors long, which allows for
 MR> 512 data bands (about 4GB).  Also in the HPFS SuperBlock is a pointer
 MR> to a spare freespace bitmap list.  What's not there is the length of
 MR> this spare list. If it's only four sectors, like the primary list,
 MR> then HPFS dies at 8GB, without another list.

The length of the bitmap list is proportional to the drive size.  On my
7.82GiB HPFS volume the bitmap list is 8 sectors long, and contains pointers
to 1024 bitmaps (of which 1002 are used).  My educated guess is that the
length of the bitmap list is calculated by the HPFS driver from the overall
volume size.

The spare list sector in the superblock is zero, by the way.

 ¯ JdeBP ®

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