Catweasel Mk1-3 not suitable for archiving - why?

[Philip Pemberton]

Hi,
   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.
[http://www.softpres.org/glossary:catweasel]

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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