dfitoimd: decoding Intel M2FM floppy flux images (was Re: Intel 432 floppy flux images for decoding)

Jay Jaeger cube1 at charter.net
Sun Aug 7 21:53:34 CDT 2016

Folks, I do have a version of software that supports READING Intel m2fm on a cat weasel, and will post a link in the coming days - just got back from a road trip.

Sent from my iPad

> On Aug 6, 2016, at 18:12, Eric Smith <spacewar at gmail.com> wrote:
> Because the cwtool support for Intel M2FM floppy disk flux images
> isn't publicly available, I've written a crude Python 3 program for
> converting such images (in DFI format) to ImageDisk images, and put it
> on github:
>    https://github.com/brouhaha/dfitoimd
> My ADPLL data separator has parameters to control the proportions of
> frequency adjustment and instantaneous phase adjustment that are done
> at each flux transition. I've experimented with the parameters quite a
> bit, but it's still not good enough to reliably recover all sectors
> from the disk images that started this thread. The default parameters
> are currently 0.5% frequency adjustment and 10% instantaneous phase
> adjustment. I was actually fairly surprised that I didn't get better
> results with more frequency adjustment and less instantaneous phase
> adjustment. It's entirely possible that my algorithm isn't very good.
> The code can handle normal IBM 3740 single-density FM format as well,
> though there are other published programs that already do that.
> There's a start at code for IBM System/34 double-density MFM format
> also, but it hasn't been tested at all as I don't happen to have any
> suitable DFI images.
> The dfitoimd program is quite slow; on a typical Intel M2FM image with
> two revolutions per track and 25 MHz sampling, it takes 64 seconds on
> a 4.0 GHz AMD CPU. I'm pretty sure that rewriting it in C/C++/C# or
> the like would make it much faster, but I specifically chose Python as
> I find it easier to experiment with the algorithms.

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