[HN Gopher] Recovering "lost" treasure-filled floppy discs with ...
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Recovering "lost" treasure-filled floppy discs with an oscilloscope
Author : scarybeast
Score : 126 points
Date : 2021-05-17 19:38 UTC (3 hours ago)
(HTM) web link (scarybeastsecurity.blogspot.com)
(TXT) w3m dump (scarybeastsecurity.blogspot.com)
| metalliqaz wrote:
| Fascinating and incredible work.
| londons_explore wrote:
| I'd be interested to see the results of mounting a much smaller
| head (eg. a hard drive head) to the floppy drive, and then
| creating a full 2D image of the disk surface magnetics.
|
| That should be able to read disks where the disk surface has
| stretched or warped, and the tracks are no longer perfectly
| circular.
|
| I think there's also a reasonable chance such a method could also
| be used to recover data on a disc that has been overwritten.
| NegativeLatency wrote:
| Related to that there are many different copy protection
| schemes and other formats for writing the data that don't
| result in circular tracks. Lots of old computers addressed the
| drive at such a low level that it was possible to directly
| control the head between tracks, and control the rotational
| speed of the disk.
|
| For example there's this project that reads stranger formats
| http://cowlark.com/fluxengine/
| chungy wrote:
| Just a little nitpicking note: the spelling of disc versus disk.
| Per dictionary definition, it's two spellings of the same word.
| Per convention, "disk" is usually used with magnetic media (like
| floppies) while "disc" is usually used with optical media
| (CDs/DVDs/Blu-ray).
|
| It took me as just a little odd to see "floppy disc" even if it's
| technically correct.
| scarybeast wrote:
| The blog post uses conventions associated with the machine in
| question, the BBC Micro, which is an iconic 1980s UK machine.
| It was pretty much "Disc" back then, e.g. the dreaded "Disc
| error 0E" from the OS, or the spelling written on the discs
| themselves, e.g. this Watford Electronics Diagnostics disc:
|
| http://www.computinghistory.org.uk/det/21293/Diagnostics-Dis...
|
| Not sure if it's a UK thing or a 1980s thing.
| robin_reala wrote:
| It's a en-GB vs en-US thing, that warrants its own Wikipedia
| article: https://en.wikipedia.org/wiki/Spelling_of_disc
| OJFord wrote:
| > Early BBC technicians differentiated between disks (in-
| house transcription records) and discs (the colloquial term
| for commercial gramophone records, or what the BBC dubbed
| CGRs).
|
| I love that.
|
| In my own usage I've always made the magnetic distinction
| without really knowing why. At least now I can identify the
| bounds as 'magnetism'..!
| egypturnash wrote:
| Fading memories of playing c64 games from both sides of the
| pond suggest that "disk" was the US spelling and "disc" was
| the UK.
| thaumasiotes wrote:
| I (American) agree with chungy; there is a strong
| convention that specifies floppy disks and compact discs.
| We could say that "disk" is the American spelling _of
| "floppy disk"_, but not that it is the American spelling of
| disc.
|
| I suspect that "disk" is used because it is shortened from
| "diskette", which wouldn't work at all if spelled
| "discette".
| egypturnash wrote:
| From https://en.wikipedia.org/wiki/Spelling_of_disc:
|
| By the 20th century, the "k" spelling was more popular in
| the United States, while the "c" variant was preferred in
| the UK. Consequently, in computer terminology today it is
| common for the "k" word to refer mainly to magnetic
| storage devices (particularly in British English, where
| the term disk is sometimes regarded as a contraction of
| diskette, a much later word and actually a diminutive of
| disk).
|
| So _in the mid eighties_ there was a distinct color
| /colour kind of split between disk/disc in the US/UK. And
| someone immersed in the world of restoring data from
| magnetic storage for a distinctly UK computer of the
| eighties? Eminently sensible for them to use the UK term,
| when everything on the computer is going to be saying
| "INSERT DISC 2".
|
| ----
|
| There are also some notes in that page on how
| Phillips/Sony's choice of "disc" for the CD has ended up
| with that being the common choice for optical media vs
| magnetic; back in the eighties this convention was not
| yet established. And then there are also sections for
| disc/disk in medical literature, and in disc-throwing
| games. English spelling is weird.
| LeoPanthera wrote:
| Disk is (or can be) short for diskette - which means a dis _c_
| in a protective sheath.
|
| Meanwhile a "disc" is any flat circular object.
|
| So floppy disk, hard disk, but compact dis _c_ , is correct.
|
| The only medium I know of that doesn't obey this rule is the
| Sony MiniDisc. MDs are definitely diskettes, and so should in
| theory be spelled MiniDisk. But presumably that's for trademark
| reasons.
| colanderman wrote:
| I had to Wikipedia what term is used for magneto-optical media.
| As much as I'd love it to be "disck", alas "disc" (as in
| "MiniDisc") seems correct in that case.
| thaumasiotes wrote:
| > As much as I'd love it to be "disck"
|
| You reminded me of the https://kol.coldfront.net/thekolwiki/i
| ndex.php/Boock_of_darc... :D
| ChrisArchitect wrote:
| yeah geez, immediate reaction. Well established just search
| around that 'disk' became standard. It's weird when someone
| writes a modern piece like this and like, the whole time they
| never noticed it's spelt disk everywhere??! It's another one of
| those things where you ask yourself "what internet do these ppl
| surf?!"
| colanderman wrote:
| Oh wow, I did not realize that floppy discs used the same exact
| encoding that was used on tape drives of the era, e.g. the
| TI-99/4A [1]. The wave file in the article is the exact same
| sound I'd listen to as a child, loading programs from cassettes.
|
| Total coincidence -- I recently have been recovering games from
| my old TI-99/4A cassettes, also using an oscilloscope (the same
| model in fact; for no particularly good reason beyond it was the
| most convenient way to record off the only tape player I still
| own), Audacity, and two open-source tools to recover such data
| [2] and [3].
|
| [1] http://www.unige.ch/medecine/nouspikel/ti99/cassette.htm
|
| [2] https://github.com/dimhoff/ti99_4a_tape_decode
|
| [3] http://www.mrousseau.org/programs/ti99sim/
| scarybeast wrote:
| Great that you're working on something similar! How are you
| finding those tools for handling degraded tape waveforms? I
| keep bouncing back and forth between hacking up my own vs.
| wanting to find some existing tool that has some clever math
| formula.
| colanderman wrote:
| Both those I linked seem to work fine, though the tapes I'm
| recovering from are mostly in good condition. The Python one
| is a bit more robust than the one included with ti99sim, but
| much much slower and picky about DC offset.
|
| (Note that both of these also decode the TI's frame format;
| but it should be easy to pull out the core waveform decoder
| of either.)
| shon wrote:
| Super cool work! Those bits are worth working to recover! Unlike
| the bits about disk/disc ;)
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