KryoFlux is an advanced software-programmable FDC (Floppy Disk Controller) system that runs on small ARM7-based devices and connects to a host PC over the ubiquitous USB connector. It reads and writes flux transitions on floppy disks at a very fine resolution. KryoFlux can read and write data with no regard for what disk format or copy protection a disk may contain. It can also read and write disks originally written with different (and even varying) bit cell widths and drive speeds - including varied cell widths within the same track -, with a normal fixed-speed drive.

If you are new to KryoFlux, you can see the info-trailer here.

Here are two teaser trailers that show the write functionality:Amiga and Atari ST

KryoFlux was written primarily with preservation of floppy disk data in mind, and so a large amount of effort was expended to create a reliable system that integrates comprehensive error detection mechanisms. This will not guarantee that the data on a disk is correct (at least, not for an unknown format) or authentic, that requires analysation, but it is very good at indicating problems when reading disks and when transferring that data to the host PC, and will also give a good degree of confidence of if the disk is in a known format.

KryoFlux is available from the KryoFlux Webstore. To see the current progress, have a look at the latest work-in-progress reports.

KryoFlux was inspired by ideas for the Cyclone20 project by Rich Aplin.

Supported Disk Image Formats

KryoFlux supports dumping any floppy disk to “stream files”, which contain the low level flux transition information present on a disk. It also supports output of a range of common “sector dumps” to allow you to use your dumped images right away in your favourite emulator. The currently supported disk image formats are:

  1. KryoFlux stream files
  2. CT Raw image, 84 tracks, DS, DD, 300, MFM
  3. FM sector image, 40/80+ tracks, SS/DS, SD/DD, 300, FM
  4. FM XFD, Atari 8-bit
  5. MFM sector image, 40/80+ tracks, SS/DS, DD/HD, 300, MFM
  6. MFM XFD, Atari 8-bit
  7. AmigaDOS sector image, 80+ tracks, DS, DD/HD, 300, MFM
  8. CBM DOS sector image, 35+ tracks, SS, DD, 300, GCR
  9. Apple DOS 3.2 sector image, 35+ tracks, SS, DD, 300, GCR
  10. Apple DOS 3.3+ sector image, 35+ tracks, SS, DD, 300, GCR
  11. DSK, DOS 3.3 interleave
  12. Apple DOS 400K/800K sector image, 80+ tracks, SS/DS, DD, CLV, GCR
  13. Emu sector image, 35+ tracks, SS, DD, 300, FM
  14. Emu II sector image, 80+ tracks, DS, DD, 300, FM
  15. Amiga DiskSpare sector image, 80+ tracks, DS, DD/HD, 300, MFM
  16. DEC RX01 sector image, 77+ tracks, SS, SD, 360, FM
  17. DEC RX02 sector image, 77+ tracks, SS, SD/DD, 360, FM/DMMFM

All this means we support pretty much any platform already: Acorn Electron, Apple, Amstrad CPC, Archimedes, Atari 8-bit, Atari ST, BBC, Commodore 64, Commodore Amiga, MSX, IBM PC, PC-8801, Sam Coupe, Spectrum, and many, many others.

Given that “FM sector image” and “MFM sector image” doesn’t sound very glamorous, let us just point out that due to intelligent handling, this supports basically any normal disk used for systems that contain a generic FM or MFM FDC - for example, all those weird synthesiser sample disk formats should work right out of the box!

KryoFlux will also eventually produce DRAFT files (not yet available, currently only raw stream files are supported), an open file format that contains the sampled flux reversals and associated information.

Stream files - see Stream Protocol - are a more device specific representation of the same data that DRAFT files would contain.

Both Stream and DRAFT files can represent any flux transition data and context information at a very high precision and detail - that means any kind of disk encoding and format can be stored in them, even if their content is not understood or supported at a given time.

Board Pictures

Here are some pictures of the product with more information on what the different connectors are used for.

KryoFlux prototype board front and description

KryoFlux prototype board back

KryoFlux prototype size comparison

Other Details

Since we are very concerned about data integrity in our own preservation work, KryoFlux allows you to check data against integrity information implied by the sector formats. It allows imaging of disks to stream files and to a more emulator-friendly image formats at the same time. So for a dual format Amiga/Atari ST disk, KryoFlux can produce stream files, a .ADF and a .ST all on-the-fly while dumping the disk. It also allows use of stream files, dumped previously, as a “virtual floppy” in order to produce sector dumps at a later time.

A rather insane amount of work has been put into this system to resolve the ongoing issues we see in the retro-computing and preservation world.

KryoFlux is named with a nod to Cryopreservation but used for magnetic flux transitions, and, umm... without the cold temperatures. It sounds cool.

KryoFlux has replaced our previous Amiga-based solution CT.

You can find out more about why we developed KryoFlux, and the original announcement. Other information on KryoFlux is contained in the work-in-progress reports, and the KryoFlux section of our knowledge base.

You can purchase KryoFlux at the KryoFlux website.