For those who don't know (as I didn't), Kryoflux is<p>> a software-programmable FDC system that connects to a floppy disk drive and a host PC over USB... reads "flux transitions" from floppy disks at a very fine resolution... the device operates on data bits at the lowest possible level with very precise timing resolution, it allows modern PCs to read, decode and write floppy disks that use practically any data format or method of copy protection to aid in digital preservation.<p><a href="https://en.wikipedia.org/wiki/KryoFlux" rel="nofollow">https://en.wikipedia.org/wiki/KryoFlux</a>
Be wary of Kryoflux:
<a href="https://www.twitter.com/textfiles/status/1057997038154121216" rel="nofollow">https://www.twitter.com/textfiles/status/1057997038154121216</a>
While Kryoflux was first at dedicated hardware, it's worth noting a software solution using Amiga 1200 was used beforehand by softpres.org to low-level read floppies, and that there's open hardware alternatives to kryoflux today.<p>Fluxengine: <a href="http://cowlark.com/fluxengine/" rel="nofollow">http://cowlark.com/fluxengine/</a><p>As an aside, for Amiga floppies specifically:<p>USB floppy controller for Amiga disks: <a href="https://github.com/jtsiomb/usbamigafloppy" rel="nofollow">https://github.com/jtsiomb/usbamigafloppy</a><p>With an Arduino: <a href="http://amiga.robsmithdev.co.uk/" rel="nofollow">http://amiga.robsmithdev.co.uk/</a>
> <i>I have come across one floppy (5¼″ low density, mass duplicated, circa 1990) where DTC reported a single track as unformatted and couldn’t read any data (there was just a bunch of zeros in the resulting image). That is, there were no errors reported at all, DTC simply decided the track wasn’t formatted. There certainly was supposed to be data on that track.</i><p>> <i>Reducing the default RPM for decoding from 300 to 295 allowed DTC to decode all tracks of the floppy without errors, including the one previously seen as unformatted. I don’t know what that’s about.</i><p>That sounds like some kind of copy protection scheme.
<i>Drives often have no media density detection and the density signal must be driven appropriately by the controller.</i><p>I seem to remember from when I briefly played around with this stuff, that the density select is used only for writing, to change the head current, but it's possible that the signal also alters something in the read path, e.g. the biasing/filtering for the head amplifier. Unfortunately I have been unable to find a schematic of a 3.5" drive to verify this.<p>Floppy drives are relatively "dumb" devices, they don't really interpret the data on the disks but just output a series of pulses corresponding to the flux transitions detected by the head. Data rate is entirely under control of the drive controller, which is what Kryoflux replaces.
it sounds like he's trying to use a high density drive to image double density floppies, which isn't a great idea. far better to use the double density drive which has the correspondingly large read/write head so you get a better signal/noise ratio.
> Forbidden<p>> You don't have permission to access /wp/__trashed/ on this server.<p>That's not at all friendly.<p>Edit: Same via <a href="https://web.archive.org/web/*/http://www.os2museum.com/wp/__trashed/" rel="nofollow">https://web.archive.org/web/*/http://www.os2museum.com/wp/__...</a> and Google cache link goes nowhere. I guess that they just don't want readers.