Re: 13-sector Disk ][ boot code AND CiderPress on DOS 3.1

[Andy McFadden <fadden@fadden.com>]

Chris Mosher <chris@mosher.mine.nu> wrote:
> CiderPress will not recognize a freshly initialized 3.1 nibble disk image. 
> The reason, I
> discovered, is that the 3.1 INIT function doesn't write data fields for 
> sectors that it
> doesn't have any data for (it only writes address fields).

This is one of those situations where you either have to weaken the
heuristic to support a rare case, or just not handle a rare case.  I
usually managed to combine a weaker heuristic with some sort of backup
test, or (for filesystem recognition) use weaker heuristics when manual
intervention is involved.

The test as written was expecting to work around damaged tracks and sectors
on formatted disks, and identify which of several encoding schemes was
used (e.g. Muse sector-number-doubling), and wasn't expecting to find
partially-formatted DOS 3.1 sectors.  I'll add "support for DOS 3.1 sectors"
to the "to do" list.

The list is long and hasn't shrunk recently, so I'm glad you found a
workaround.  The real fix might involve scoring address and data fields
separately, with data fields on 13-sector disks being weighted less than
address fields.  (The risk is incorrectly identifying a copy-protected
disk with valid address fields but altered data fields.  We also need to
see *some* data fields or we won't know if it's supposed to be 5+3 or 6+2.)

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