Low-level floppy di...
 
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Low-level floppy disk reader?

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(@matthew_exon)
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Joined: 18 years ago
Posts: 3
Topic starter  

I have some very, very old Macintosh floppy disks that essentially have my childhood on them, and I'd like to recover as much as I can. I bought an old Mac SE so that I could try reading the disks, and unsurprisingly most of them are more-or-less unreadable (others, encouragingly, work fine). I have not yet given up hope of recovering the missing files, but I think I may have reached the limits of what this Mac SE will do for me.

It occurred to me that you could build a special floppy drive designed for data recovery, which sent a high-resolution real-time digitised version of the analog signal from the head, instead of just a sequence of ones and zeroes. Then you could write software to perform more sophisticated data recognition, rather than just looking for magnetic fields above or below a threshold.

And then it occurred to me that I can't be the only person in the world trying to recover data from 80s-vintage floppy disks, and that computer forensics people probably do this kind of thing all the time.

So I have two questions

1) Are there any shrinkwrap solutions to this? I can imagine that there are specialised machines designed for professionals, and that they're probably too expensive for me. It'd be interesting to know.

2) Perhaps naive of me, but wouldn't it be possible to home-brew something here? I envision taking an old floppy drive, ripping out most of the electronics, and replacing them with some kind of generic USB sensor thing. Then it would "just" be a question of writing the software to control the drive manually and interpret the analog signals.

Thanks for any suggestions,
Mat


   
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azrael
(@azrael)
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Joined: 19 years ago
Posts: 656
 

A quick suggestion - the original Mac SE doesn't support 1.44mb floppy disks, only 800k ones. The 1.44mb HDFD drive wasn't shipped until 1989, so if you have an older one ( the SE was released in '87 ), a later disk would be unreadable, without necessarlily being damaged.

http//lowendmac.com/compact/se.shtml

Just a possible direction to look in -)

Try a later Mac which should ( in theory ) be backwards compatible …

Good Luck.


   
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(@matthew_exon)
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Joined: 18 years ago
Posts: 3
Topic starter  

No, these disks are really old. None of them are 1.44MB floppies. Mostly they're 800k, some of them are even 400k. That's why I had to go to all the trouble of buying an old Mac SE there's no way to read these things in a standard modern floppy drive.

In fact, my SE does have a FDHD drive. This is how I've been transferring files from the SE to the PC image the 800k disk, copy the image to a 1.44 disk, copy back onto the PC. It's a tedious process -(


   
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azrael
(@azrael)
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Joined: 19 years ago
Posts: 656
 

http//forums.macrumors.com/archive/index.php/t-220052.html

This seems to suggest that it may not be elementary -(


   
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(@matthew_exon)
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Joined: 18 years ago
Posts: 3
Topic starter  

Indeed, it isn't. Mac drives employ sophisticated mechanisms to vary the speed of rotation dependending on whether they're reading the inner or outer tracks, so that they can squeeze more data onto the outer ones.

But I'm suggesting going even deeper than that, since I'm dealing with disks that are damaged anyway. I want to spin a disk, attach a digital oscilloscope or something similar to the read head, and record the raw analog stream of what happens as a particular track spins underneath the head. Then I'd be able to interpret a waveform such as

…as 01010101010, with the middle part being damaged by a magnetic field or some such.

Helpfully, Macintosh and PC disks both seem to have the tracks in the same position, so the same stepper motor will work.


   
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