I have a floppy disk with an unknown FS-(FileSystem). I want to make a copy from it but I can't because both Windows and Linux seem to be unable to read from it.

I tried many of the most popular apps to make image files (for example isomeric, winimage, ...) but they are all unable to make an image.

On Linux I tried the dd command to copy it but it seems that not even dd is able to make a copy. I get many errors while reading from the disk, I looked them up and I found that dd was unable to read from it because of a bad sector - but when I test this floppy on the HITACHI system it works fine and I don't get any error.

The question is: how can I make a copy from this type of floppy? I've heard I can use a BIOS interrupt for this kind of things?

  • 1
    Sounds like the floppy is damaged and unreadable. What do you mean by "test the floppy on the HITACHI system"?
    – Ex Umbris
    Mar 15, 2012 at 17:39
  • 1
    Or better on Super User
    – Ex Umbris
    Mar 15, 2012 at 17:40
  • i mean we unable ro read because of bad sector!becouse of bad sector, but hitachi systems can read it, more information about hitachi system : gmi-inc.com/Roche-Hitachi-912-Chemistry-Analyzer.html any other question?
    – repozitor
    Mar 15, 2012 at 17:41
  • 1
    You said that on the "HITACHI" system it works fine... what is "the HITACHI system"?
    – Ex Umbris
    Mar 15, 2012 at 17:42
  • Either your floppy is damaged or your floppy drive is bad. It's a hardware problem either way. Mar 15, 2012 at 17:43

5 Answers 5


If dd and other raw read utilties don't work, it's highly likely that the disk sectors are bad - in which case no method of reading (BIOS interrupts or otherwise) will work.

How did you determine that the test on a Hitachi system "works fine"?

You could try the "noerror" option with dd to read the disk, but you'll only get partial data if read errors occur.

  • i use no error, and no trunk and .... :D, i try it with all option of dd
    – repozitor
    Mar 15, 2012 at 17:48
  • 3
    Do you know if the floppy disk itself is a standard 3.5" or 5.25" type? If the disk has an unusual track layout or strange sector sizes, it may explain the failures.
    – adelphus
    Mar 15, 2012 at 17:51
  • this floppy is 3.5" and when we format it under fat21 it work nice with linux and windows, but when i put hitachi data on it, it seem have a magic format that windows unable to read it
    – repozitor
    Mar 15, 2012 at 18:00
  • adelphus: how dd read sectors from floppy? by FS or without FS? i mean "dd" read sector by sector or by file system?
    – repozitor
    Mar 15, 2012 at 18:04
  • @repozitor: dd reads what you tell it to read. If you give it the raw device file /dev/fd0 as the input, then dd reads raw sectors.
    – user1686
    Mar 15, 2012 at 19:26

What is this "HITACHI" system? Is it a PC? A piece of music equipment? Industrial controller equipment? A video game?

That particular system may use a unique low-level format on the floppy. For instance, there are MFM formats and some older systems used GCR. I don't think the PC floppy controller can do GCR at all but I'm not sure.

You may need a special utility that works with the drive controller on a lower level to read the data. For example, the Q-80 MIDI sequencer has a 3.5" floppy drive, but the format cannot be read on a PC unless you can dig up the q80util.exe someone wrote - and it only works on DOS/Win9x due to direct access to the floppy controller.

  • with which way i can found what is the real format? and these floppy used for below system linked : en.wikipedia.org/wiki/Hitachi_917
    – repozitor
    Apr 6, 2012 at 11:35
  • If you know someone who actually has a 917, see if they have a sales or service contact that can get you in touch with a conversion tool. Some brief googling on my part shows the 917 can send data out via a serial port and maybe it can dump a disk over the serial as well.
    – LawrenceC
    Apr 6, 2012 at 13:44
  • 1
    Also noticed in the specs here centralizeddiagnostics.cl/Equipos/docs/RH917.pdf that the "control unit" is a Windows PC running NT with a Pentium II processor? If the floppy drive is connected to that control unit, the disk is likely a standard PC MFM format - and the reason why you can't read it is because the disk is bad or the original drive was out of alignment when it was written (common as floppy drives age). May need to go to original machine to try to get the data.
    – LawrenceC
    Apr 6, 2012 at 13:47
  • Well, looks like @Rob beat me to it, that's what I get for not scrolling down...
    – LawrenceC
    Apr 6, 2012 at 13:49

Based on the original specs of your machine, the control unit is a Windows NT PC, so whatever the software is writing to the disk should be readable on another PC.

It's highly likely that there is a head alignment problem or some other hardware issue with one of your floppy drives. If this is the case, the Hitachi machine's disk drive would be able to read what it writes, but your other drive may not. Here are a few things to try:

  1. Replace the Hitachi machine's floppy drive, save your data to a new diskette, and try reading that diskette in your other machine.
  2. Replace the other computer's floppy drive and see if you can read the data on your existing diskettes.
  3. Move the Hitachi machine's floppy drive to a different machine, then see if you can read the data on your existing diskettes.

I worked on these systems before and the answer is simple: Hitachi format these diskettes in a special manner not recognizable by Windows or Linux (sectors/tracks) so both of them will keep insisting that floppy is bad but when you pop it into the machine it will work perfectly. There is nothing wrong with disk or drives. For your question of how to copy it I am not sure you can using a pc but you can do that using some Hitachi machines themselves but not all do this. Yes the machines are controlled by an Win NT PC but the floppy is inserted directly into a drive inside the machine and not into the PC.


If you have access to an old PC with DOS, try DiskDupe Pro or FDA (Floppy Disk Analyzer), these tools were able to copy many copy-protected floppies in the old days. FDA also supports non-PC diskettes.

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