Disc Imaging / Kryoflux - Acorn ADFS 800KB

Fred Cisin cisin at xenosoft.com
Sat Jul 2 14:25:08 CDT 2016

On Sat, 2 Jul 2016, Austin Pass wrote:
> Thanks for the feedback Fred.
> The Kryoflux Forums are admin-approval-only and I've been waiting a couple
> of days for that to happen.
> To the best of my own knowledge it's a pretty standard MFM, as the
> computers featured the Western Digital 1770 and 1772 controllers.
> The specific discs I'm trying to image are 800KB "double density" designed
> for the 32 bit ARM based computers.  I can't find any 720KB PC floppies,
> but I'll follow the methodology with 1.44MB HD ones to see where it takes
> me.

Although there will be a slight loss of long-term reliability (not an 
issue here), you can cover the media sensing hole of a 1.4M diskette and 
format it into 720K
FORMAT B: /F:720
FORMAT B: /T:80/N:9
(all do the same thing)

Then copy some files to it, so that there will be something interesting to 

That will be similar enough to the Acorn diskettes (if we are right about 
the details of the Acorn format).
AND, then if those don't work either, then the Kryoflex forums won't get 
sidetracked into thinking that it is an Acorn issue.
I think that THAT would be inevitable if you don't separate out whether 
the problem is with Kryoflex V Acorn!

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)

If so, then it should be feasible to copy sectors from those disks in 
MS-DOS on a 5150 or 5160, using INT13h.   Don't know whether it could be 
done in Windoze8.

AFTER you get it working for all functions that you need with simple 
stuff, you should be able to do 8" with it.  The 8" interface and behavior 
is virtually identical to that of a 5.25" 1.2M!
Only a few pins need rearrangement on a 50 pin to 34 pin cable.
If you want to WRITE to 8", then you may want to also deal with TG43.
There is a commercial adapter (FDADAP) for that, which would also take 
care of the rest of the cabling.
Be aware that power supplies are not standardized for 8"; you'll need to 
make your own if you get a drive without one.

Grumpy Ol' Fred     		cisin at xenosoft.com

More information about the cctalk mailing list