2M disks where formatted using 2MGUI to increase 3"1/2 & 5"1/4 DD/HD/ED disks' capacity.

Is there any way today to recover/dump these disks to a file with modern hardware? Specially the 5"1/4 ones...

I've got both kind of floppy drives but not controllers.


Adding a link to a tool suit to manage 2M disks under linux named Gtools

You can read more about here (spanish only).

4 Answers 4


In my experience, your best bet to read 2M/2MGUI disks is to find an old PC with a built-in floppy controller, and run either DOS (with 2M and 2MGUI) or Linux (with Mtools, which supports 2M formats) to try to read the disks. Even then, some 2M disks will be hard to read — beyond the usual problems with old floppy disks, since 2M formats really push the limits, it can be difficult to read a 2M floppy using any other drive than the one which wrote it.

There are a few “modern” options you could try, although both will require some work. If you’d like hardware you can buy, you can use devices such as the Greaseweazle, Applesauce (currently a victim of the global chip shortage), Kryoflux or SuperCard Pro to read the raw data from the disks; or if you don’t mind building your own, give David Given’s FluxEngine a go (you can also build a Greaseweazle yourself). Once you’ve got the raw data, you’ll need decoding software for the 2M formats. I’m not aware of any existing 2M decoding software for raw streams, but I haven’t been paying all that much attention to 2M recovery; take a look at Keir Fraser’s disk utilities to get started if you feel like writing your own.

  • 1
    Using Mtools might be the best way to get it going. Great idea!
    – Raffzahn
    Commented Oct 1, 2019 at 13:57
  • Thanks @StephenKitt, I will try. I've all components except mainboard.
    – NataliaPC
    Commented Oct 2, 2019 at 8:50

I'm not sure if this is technically possible for the disk format you are asking about, but there is an open source project by David Given called FluxEngine that has been trying to read all kinds of weird and exotic disk formats by reading the magnetic flux changes directly - creating a sort of 'disk image' that can then be deciphered in software to reconstruct the actual data. I'm only following the project tangentially, and the Github page does not mention the disk format you are interested in - but you might try contacting the author and asking about the viability of reading your 2M disks.


There is any way today to recover/dump to a file these disks with modern elements? specially the 5"1/4 ones...

Only by using the same drive/controller combination with the 2M Software. Especially the controller is important, as the software bypasses regular format to increase density, which may not be possible with newer hardware.

I've both kind of floppy drives but not controlers.

Controller may be found at scrap dealers or eBay. But without the software it won't work at all.


Linux systems can support a lot of hardware floppy formats (maybe not ALL that these old tools offered), that is what the various fd* (eg fd0h1722) devices in a classical /dev filesystem are meant for. See the fd(4) manual page. If the format you use is supported, you will be able to simply mount the appropriate device as the appropriate filesystem (vfat, likely).

Your mileage may vary; a built in 34pin port on an older mainboard, plus a 34pin floppy drive, will likely yield more success than usb connected drives.

Mind that using such above-normal-capacity formats made the resulting disks extremely liable to problems from media defects, drive calibration errors, or subtle hardware differences. That is why they were not used for mainstream applications.

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    USB floppy drives are guaranteed not to work for this purpose, because USB only supports a small number of disk formats, which don’t include 2M formats. As for fd, while it does support many extended capacity formats, it doesn’t support 2M formats. Commented Oct 2, 2019 at 4:30
  • Ī̲ concur that Linux (assuming fd0 or fd1, that is, a “physical” FDD controller) deals with various floppy-disk formats having uncommon numbering of sectors and the sector size alike. Unfortunately Ī̲ don’t have detailed information at the hand now (remember only that it requires some ioctls). Commented Mar 28, 2021 at 16:25

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