Disc Imaging / Kryoflux - Acorn ADFS 800KB

Austin Pass austinpass at gmail.com
Sun Jul 3 07:41:40 CDT 2016

On Sat, Jul 2, 2016 at 10:15 PM, Peter Coghlan <cctalk at beyondthepale.ie>

>> Is the capacity of the diskette 800K? or is that merely the name of the
>> type of the diskette, with an actual capacity of somewhere between 640K and
>> 800K?
>> If the actual capacity is 800K, with MFM, then it would probably be 80
>> track, double sided, with either 10 512 byte sectors or 5 1024 byte sectors
>> per track.  (can't get up to 800K with "normal" WD style MFM with 256 bytes
>> per sector, and 512 byte sectors are a little tight)
> The original ADFS had 16 sectors of 256 bytes per track. However, it
> appears
> that more recent ADFS formats use 5 sectors of 1024 bytes.  There are more
> details here:
> http://mdfs.net/Docs/Comp/Disk/Format/Formats
> Regards,
> Peter Coghlan
Thanks everyone.

All working now - there were two issues at play.

1) Wrong settings for DTC.  Used the linked-to document to change to
1024Byte sectors, tracks 0-79 and sectors 0-5.  I record the stream file of
flux transitions as before (a preference in any event) and when I process
it with the aforementioned settings I get an 800KB .adl image file.  This
mounts up in an emulator very nicely:


2) The initial disc I used was an original disk for a game - SWIV.  I
suspect that it either uses some interesting copy protection mechanism or
the media is faulty.  The above method works for 9/10 discs but not the one
I originally selected for testing.  Lesson learned - use known good media
or a selection of suspect ones.


More information about the cctech mailing list