Another disk imaging project

Patrick Finnegan pat at
Wed Aug 3 10:27:01 CDT 2005

On Wednesday 03 August 2005 09:53, Dave Dunfield wrote:
> >> The idea is to make a small single-board computer with a
> >> microcontroller, a WD2793 or similar floppy disk controller,
> >> enough memory to buffer a few tracks, and a high-speed serial port
> >> for communication with the PC. The board would have connectors for
> >> 5.25"/3" drives and 8" drives, and would properly interface to all
> >> drive types.
> >
> >Dave, why not just write software for a catweasel card?  I realize
> > that the catweasel's FPGA has been programmed with a bitmap made
> > from closed-source RTL, but is that a serious impedement?
> Yes. - What happens when the catweasel becomes unavailable?

What happens when (disk controller of choice) become unavailable? :)

> >When the day comes that the catweasel is no longer supported/sold,
> > it would be possible to at that point design another one.
> Will it? Or will nobody bother as it's a tough job.
> Will it be 100% compatible, or will we find that disks that were
> created with this at-least partially proprietary system will be
> "lost" if the system cannot be made to work?

The people making it aren't a "huge corporation", they're just regular 
people, and I'm sure you could talk to them about such things.

> >The catweasel is here and  real, and at $100, it is price
> > reasonably.
> The $100 cost, and the fact that you have to order and wait for it,
> means that a significant number of people won't bother (I haven't) -
> something you can build in a few hours in your workshop at near-$0
> cost will get done by more people.

Fine, buy one off ebay for less than $100, and get it within a week.  
That's what I did.  The catweasel is a great product for its price, 

I don't have enough parts in my junk bin to build a disk controller, and 
there's a lot of people that don't have the skills to assemble 
something like that.

> Is the cat software open-source, are the internal and storage formats
> fully documented - one big thing about the work that I have been
> doing is to make sure that people in the future can access the data
> from the images so that they can find "other means" of regenerating
> the disk if necessary - even if that regenerated disk is just a
> different format image for a simulator.

Yes, otherwise it wouldn't work with any formats.  The whole point of 
the catweasel is that 3rd parties write software for it to decode disk 

> >Sure, not everybody will
> >be able/willing to spend $100 for something like this, but that is
> > far less than the number of people who would be put off by having
> > to build their own hardware.
> On this point I disagree - the board I am thinking of would be very
> simple, perhaps a dozen DIP chips - easy to build. I think a lot of
> the people on this list would gladly take an evening or two to build
> one - also if it were to be done, printed circuit boards, and even
> finished/tested boards could be made available at low cost (like the
> cat), but unlike the cat, fully documented and you can build it
> yourself if you like. It would not be "owned" or controlled by
> anyone.

I know a lot of people that wouldn't build ANY hardware.  Even more 
people (like myself) would rather spend the money for a catweasel than 
try to find parts and build something that doesn't have the 
functionality of a catweasel.... Do you think you'll get your WD chip 
solution to read Apple ][ or C64 (1571-written) disks?  I'm doubtful at 
best.  That's a huge volume of the disks I've got laying around and 
eventually want to make images of.

> >The one thing that I feel is missing from the catweasel is a 50-pin
> > header for connecting to standard 8" floppies.
> A grave omission for something thats supposed to archive
> non-PC-standard disks.

If you're supposing the user can wire up a disk controller, why can't 
they wire up a simple 34(SA400) to 50(SA800) pin adapter cable?  Also, 
you can buy an SA400/SA800 adaptor board that someone has made, which 
properly controls the TG43 line.  Unfortunately, I can't remember the 
name of the board or who made it right now.

> >Another minor gripe is that each of the  versions of the catweasel
> > (now four) tries to be register compatible with previous versions
> > while adding new functionality.  It has lead to some arcane 
> > programming requirements, which is sad: a very thin API to hide
> > version changes  would have made things much simpler.
> But would have tied the thing to one particular development
> environment (Here's you VisualC++ library - have a nice day). The
> best solution is a fully open and documented description of the
> hardware and lots of sample code.

There's no reason a bit of C wrapper code has to be tied to any 
particular 'development environment'.

> >Finally, is the WD2793 able to read northstar horizon floppy disks? 
> > If not, then a WD2793-based solution is not general enough.
> As noted in the original message, it would be soft-sector only - the
> idea is to make a simple/cheap alternative to the limitations of the
> PC controller...

I'd say that by ignoring (specifically) Apple ][ and C64, you're missing 
a large percentage of possible software/users.

> Still deciding if it's worth it - I'll record your "NO" vote.

Not to discourage you, but, I'd echo the sentiment above.  I'd suggest 
that if you do want to produce something, make something that can read 
the disk on a flux-transition level, and store that sort of data.  
Something nice and generic.  That way, you can do all the processing in 
software, and handle any format of disk that comes your way.

Purdue University ITAP/RCS        ---
The Computer Refuge               ---

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