Re: Extracting files off “unknown” 8 inch disks. Any thoughts…

[Chuck Guzis]

On 04/17/2017 09:20 PM, Fred Cisin wrote:

> Is track 0 sector 1, formatted as 512BPS? If not, how does it even
> come up with the idea to try 1024BPS? (in order to read it, to find
> out that it should try it for reading it...)
> 
> (at location 0Bh in the BIOS Parameter Block, is the bytes per
> sector, but unless that sector is 512BPS, how did the OS read it to
> know to use that?) BPB doesn't include the number of tracks, but it
> does have the sectors per track, heads, and total number of sectors.
> It also has the "Media Descriptor Byte", but I wouldn't rely too much
> on that.)

No, the whole disk is 1024*8.   The first sector starts off like this:

000000  EB 1C 90 4E 45 43 20 32 2E 30 30 00 04 01 01 00
000010  02 C0 00 D0 04 FE 02 00 08 00 02 00 00 00 33 C0

I remembered that I wrote a NEC PC98 disk format driver for MS-DOS.
It's probably in SIMTEL20; it's called "NECSYS",

It will not only read and write PC98-format floppies, but will also
format them and deposit a PC98 boot in the first sector.

As I recall, NT/2K/XP will read PC98 floppies if they're in an Imation
LS120 Superdrive or in a conforming  USB floppy drive.  I don't know
about legacy floppy controllers.  It might also work in a Caleb HD144
drive; I haven't checked that out.

--Chuck