Wednesday, 1 April 2009

An update on my data recovery efforts

You may remember that after our Christmas party late last year, I wrote a blog post offering to have a go at recovering some old files, if anyone was interested. A half dozen or so people got in touch, one with 30 or so old Mac disks, someone with a LaTeX version of a thesis on an old Mac disk, a colleague (who started all this, really) with a dissertation on an old Amiga disk, and someone with a CD from an Acorn RISC PC, plus a few others.

I frightened some off by giving them a little disclaimer to agree to, but others persisted and sent me their media. So, problem number 1, how to read old Amiga and Apple floppy disks? Both of these have a different structure from PC-compatible floppies, for example the old Mac disks store more information on the outer tracks than the inner ones, thus packing more data onto the disk.

The answer seemed to be a special controller for a Windows computer, that links to a standard floppy drive. The controller is called the Catweasel Mk4, from a German company, Individual Computers. We ordered one and it arrived quite quickly, well before I had managed to borrow a Windows box to experiment with. The card didn't physically fit in the first system, and then there was a long wait while we found a spare monitor (progress was VERY slow when I had to disconnect and re-use my Mac monitor). Then bid-writing intervened.

Eventually we got back to it, but had lots of problems configuring the controller properly; the company was quite good at providing me with advice. Finally a couple of days ago I finally got the config file right.

I wasn't using any of the contributed disks for testing, but instead some old DOS disks that I had from my days in Dundee (1992-4). Early on we did manage to read these, with rather a lot of errors, but lately we have got zero good sectors off these disks. I'm still not sure why; I'm inclined to blame my attempt to read one of the disks using the Windows commands on the same drive (there's a pass-through mode); I never managed to get any DOS disks to read a single track after that!

Well, today I stuck in an old Mac disk I had... and lo and behold, it was reading with a fair proportion of good sectors. So, let's try the Amiga disk: 100% good (well, maybe one bad sector). And the Mac disk with the LaTeX file on it: pretty good, 1481 good sectors out of 1600.

The problems aren't over yet. All you get from the ImageTool3 program that works through this controller is a disk image. So now I'm looking for a Windows (or Mac) utility to mount an Amiga file system, so we can copy the files out of it. And ditto for the Mac file system (written circa 1990 I think; I'm assuming it's HFS, but don't know).

At that point, depending on the amount of corruption, the Mac job should be pretty much done; my contributor still understands LaTeX and can probably sort out his old macros. For the Amiga files, there will be at least one further stage: identifying the file formats (CV.asc is presumably straight ASCII text, but the dissertation may be in a desktop publishing file format), and then finding a utility to read them.

It's been slow but interesting, and I've been quite despondent at times (checking out the data recovery companies, that sort of thing). But now I'm quite excited!

These two contributors have got their disk images back, and may have further ideas and clues. But can you help with any advice?


  1. Hi Chris,

    You might want to look into the Amiga emulation community. They have been imagine Amiga disks for years which they then access through an emulator such as winuae (
    Amiga Forever are a commercial company who sell amiga rom images for use with these emulators alogn with other software that might be needed for accessing the files on that amiga disk.
    You might be able to create an image of that disk and access it through an amiga emulator.



  2. that was "imaging", not "imagine".

  3. I've just had a look at the amiga forever website and they have a lot of info about accessing amiga disks.

  4. Hi Chris,

    maybe it is not the solution you wanted for the HFS-image, but...
    Why not use a Knoppix-Linux ( or any other Linux-Live-CD and mount the copy(!) of the HFS-image as loop device?
    Maybe a modprobe hfs or modprobe hfsplus must be handed over to the system before mounting the image.
    This seems for me the easiest and most promising way to solve this task.
    An option for Windows Users might be the Shareware Transmac (, Website only in german), but I did never test it.




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