Catweasel Mk1-3 not suitable for archiving - why?

Andrew Lynch lynchaj at
Mon Sep 17 18:32:27 CDT 2007

   I've been doing some more work on the FDD
reader/writer, and I came across 
an interesting note on the Software Preservation
Society website:

> We cannot yet support the Catweasel for technical
reasons, primarily because
> it does not yet enable us to read disks in
sufficient detail for dumping, nor
> does it allow writing IPF files back to disk. And
while it does seem that the
> Mk4 would be suited to the job, current models are
still running Mk3 firmware
> and drivers, meaning that we are still no closer
forward in this regard.
> As soon as Mk4 firmware is available for these
cards, we will do our best to
> obtain one with a view to support it for these
purposes. Until then, our hands
> are tied.

Now what I'd like to know is, what part of the
Catweasel's design prevents it 
from being used for archiving discs?

 From what I remember, the Amiga FDD controller is a
bog-standard raw reader 
with an MFM sync detector. All it does is sync up to a
bitstream and read it 
from the disc as a raw stream until it gets told to A)
shut up or B) receives 
another MFM sync.

 From what I've read, the Catweasel differs only in
that it measures the 
timing between bits, and can do MFM pre-decoding. So
what part of its design 
makes it such a bad choice for this kind of work?

FWIW, I'm almost at the point where I can start
thinking about doing the PCB 
designs for the USB floppy disc reader/writer. I've
found a solution to the 
lack of I/Os on the microcontroller (which involves
adding a second CPLD to 
act as an bus expander - probably over I2C). I'm going
to do some testing on 
the bus expander Verilog code tonight, and update the
schematics, then any 
spare time I get next week will probably be spent
working on the PCB artwork. 
My intention is to take a weekend off work at some
point in the next month to 
build up the prototype and do some coding and testing.
If all goes well, I 
might do a small production run in November, depending
on interest.

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Copy and paste Bunny
classiccmp at      | (='.'=) into your
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I have seen the SPS website you mentioned and read
this thread but for the life of me I cannot understand
why the Catweasel would be unsuitable for archiving
vintage computer floppy disks.

If fact, I think a Catweasels raw "bit dump" would be
the idea archiving format since it records all the
details found on the track.  Maybe wrap the raw data
in a container format with metadata like the DMK.

With Catweasel, you can see everything on the track
clock, data, junk, etc. Whatever is there you can see
it in the raw data.  Once you have the raw bit dump
you could make near identical copies or write programs
to extract the data files, work with emulators, etc.

Regardless of the SPS position, I know some people are
already using the Catweasel for archiving vintage
computers.  Tim Mann's software pretty much covers the
almost the whole soft sector disk format spectrum and
Jim Battle made a SOL-20/PTDOS hard sector disk
imaging program.  I think someone else made a program
to archive Data General disks.

Catweasel seems like the way to go to me.  If there is
something else out there as good, especially for the
hard sector disks, I would certainly like to hear
about it.

Has anyone tried Disk2FDI on any hard sector formats? 
It sounds interesting and inexpensive if it works.


Andrew Lynch

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