[vcf-midatlantic] How To Geek article on floppy data recovery

Herb Johnson hjohnson at retrotechnology.info
Wed May 20 17:08:48 EDT 2020

Reply to David Gesswein:

Sorry for the delay in reply, I work offline from this discussion group, 
and don't read it daily as most do. I always appreciate the informed 
views of my good friend David. Especially so in this case because, as he 
points out, he is a producer of similar tech, for MFM hard drive data 
recovery *and* emulation. He knows more than I.

I acknowledge the value of lower cost. But it creates a market where 
more costly solutions are discouraged. He discusses cost AND time, as 
user issues. Some people give up their time, to save costs; some give up 
costs to save their time. But more buy cheap, and sometimes audience 

A consequence of inexpensive items is that most do not stick around 
long. that's why I brought it up! But others can try to recreate them 
when they aren't available  (reliably). Thus the "blue pill" 
Greaseweasel saga, seems to be, to either build a more reliable one (use 
the proper CPU chip); or to build one on a better CPU (to move forward). 
My thanks to Jeff Jonas for passing along some Facebook/greaseweasel 
info, that is where they congregate.

"the projects don't cooperate" is a problem, as David describes. I 
agree. Developers tend to redevelop rather than rework. Also, old stuff 
gets lost, or may be hard to recover for redevelopment. This is true in 
most technology; it's ironically true in vintage computing, but 
thankfully not always.

"most of the value is in the decoding code". The value is split, between 
the enabling hardware to do the read; and the enabling software to 
decode the sampled flux-patterns. The historic example of the Catweasel 
series, is that the hardware producers did not make popular decoding 
software; others did. I did not determine if the FOUR or FIVE developers 
of Catweasel decoders, cooperated much or not. Each grabbed some piece 
of vintage computing disks by brand & model (TRS-80 for instance).


"I image with real hardware when I have it". Yes, that was the ultimate 
solution for Intel M2FM disks, which at one point were imaged by 
Catweasel. The images were reproduced as floppies, and read again on 
Intel systems! I'll contact David privately for more information about 
his imaged disks, to route his results to active INtel Multibus


Of course, we in vintage computing are generally interested in "real 
hardware". But I get

pushback often, in advocating use of period PC-compatibles to image 
conventional diskettes (made with Intel/NEC/WD floppy disk controller 
ICs) with Dunfield IMAGEDSK tools. "I hate old PC's!" is the most terse 
way to describe that. Thus the value of microcontroller based floppy 
drive emulators and floppy recovery hardware. Well, each of us chooses 
our areas of vintage interest.


I had private discussions of the topic, with "Gordon S." AKA gsteemso. 
He was of a mind, that some kind of vintage-hardware solution for floppy 
recovery had some merits. I think it will be a challenge to make such a 
thing at the price of a few tens of dollars, like the other 
microcontroller solutions. But a solution like the Greaseweasel is a 
$200 built-for-you solution; some floppy emulators sell for that price. 
So: a re-vintaged solution is conceivable, but I don't think it would be 

At this point, the discussion is a matter of specifics and techie 
details. A little too much so, for general email discussion lists like 
this, I believe, and the thread seems to have died down. If that's 
because I didn't reply and took some discussion privately, my apologies. 
I hope those participating were informed as I was, and those interested 
can find more information as they see fit.

Regards, Herb Johnson

Herbert R. Johnson, New Jersey in the USA
http://www.retrotechnology.com OR .net
preserve, recover, restore 1970's computing
email: hjohnson AT retrotechnology DOT com
or try later herbjohnson AT retrotechnology DOT info

More information about the vcf-midatlantic mailing list