Actually, you might find that an electromagnet works faster. Years ago, a
friend tossed his only copy of some sort of data that he'd produced onto an
Apple "graphics tablet." That bulk-erased it very nicely. I don't remember the
details, but it apparently had a moving magnetic field that it sensed in some
way with the "pen" it used. ... Unfortunate way to learn about this, I guess,
but there's a message there for those wishing to "clean" their otherwise
unformattable diskettes.
Dick
----- Original Message -----
From: "Sipke de Wal" <sipke_at_wxs.nl>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, October 31, 2001 2:44 AM
Subject: Re: Jeez... was (Re: hard-sector 5 1/4 disk)
> On the other hand ..............
>
> I have a very large permanent magnet from the
> voicecoil assembly of a scrapped laundrymachine-sized
> diskdrive (which I took apart 12 years ago!).
>
> Whenever I have a tape that I need to reformat but
> that refuses to do so, I'll leave it on the magnet for a few
> hours and presto.... I will reformat afterwards!
>
> Strong magnetic fields are never a good environment
> for preserving data on magnetic media!
>
> Sipke de Wal
> --------------------------------------------------
> http://xgistor.ath.cx
> --------------------------------------------------
>
> ----- Original Message -----
> From: Ian Koller <vze2mnvr_at_verizon.net>
> To: <classiccmp_at_classiccmp.org>; <UberTechnoid_at_home.com>
> Sent: Wednesday, October 31, 2001 8:27 AM
> Subject: Re: Jeez... was (Re: hard-sector 5 1/4 disk)
>
>
> >
> >
> > I tried an interesting experiment once. I put a floppy disk
> > on the magnetic chuck of a surface grinder, a magnetic field
> > strong enough to hold a workpiece in place while grinding it,
> > and after cycling the power a few times, went to try to read
> > the disk. I expected it to be well erased, like using a bulk
> > tape eraser, but to my surprise, the disk read o.k. Perhaps
> > the disk needed to be moved around in the field more before
> > it would have been erased? But with the instructions on disks
> > saying to keep them away from magnetic fields, it sure surprised
> > the heck out of me because that was one pretty strong magnetic
> > field.
> >
> >
> >
> >
> > UberTechnoid_at_home.com wrote:
> > >
> > > I've seen some unreliable disk drive interfaces in my time. Most notably
> > > the ATR8000 and the Percom drives for Atari computers. They supported
> > > everything but the data was only readable for about 15min.... Seriously
> > > though, we ran the Tardis BBS in Miami, FL on an ATR8000 for more than a
> > > year. Frequent backups were required.... I've tried using one off and on
> > > as a main drive, and no matter how cool the ATR is, it can't store it's
> > > own data in CP/M or as an Atari controller to save it's life.
> > >
> > > As for the apple and atari drives, I have an experience I'll relate that
> > > makes me GOGGLE at what I just read from RIchard.
> > >
> > > A student while I was a student teacher in Jr high claimed that floppy
> > > disks were so very fragile that he would throw away a good floppy after
> > > dropping it on his desk just once. I opened two floppy disks, drew out
> > > the platters, rubbed them vigorously with a pencil erasor, dusted them
> > > off, inserted the platters 'naked' and read them. One into an Atari 810
> > > and the other into an Apple Disk II drive. Both worked of course. Talk
> > > about abuse!
> > >
> > > I wouldn't reccomend this for data you want to read twenty years from the
> > > day you wrote it, but the systems are that strong. I too have hundreds and
> > > hundreds of Atari disks (90k to 720k) disks that are perfectly readable
> > > ten or fifteen years later. What would I do without the "BIG demo"?
> > >
> > > Regards,
> > >
> > > Jeff
> > >
> > > In <000f01c161ba$ad656800$9cc762d8_at_idcomm.com>, on 10/30/01
> > > at 08:18 PM, "Richard Erlacher" <edick_at_idcomm.com> said:
> > >
> > > >you said " ...
> > > >>
> > > >> No, it is not conceivable, since there is no light and photocell to
EVER
> > > >> EVER see the index pulse.
> > > >>
> > > >..."
> > > >I have to disagree, actually, because the Apple diskettes all seem to
> > > >have the holes, not that it matters. While the drive may not have the
> > > >means to "see" them, since it's about ignoring them, the inability to see
> > > >them makes them easier to ignore, which, in turn, explains why someone
> > > >might happily use hard sectored diskettes in an Apple][. That was the
> > > >point about which there seems to have been some confusion.
> > >
> > > >and " ...
> > > >Except that they did too much in firmware, . . .
> > > >..."
> > > >Which, admittedly, I don't understand, since the PROM they used was
> > > >rather small. (...that's where the firmware lives, doncha know...) Most
> > > >of the work was in the software, actually, since it had to do what the
> > > >disk format required, and figure out along the way which one it was.
> > >
> > > >I've never liked Apple-disk-related problems, since the Apple system was
> > > >incredibly fragile and highly unreliable. The first Apple client I had
> > > >who had been using an Apple][+ in his business summarily took his ][+,
> > > >drives, and monitor, the whole shebang, out to his dumpster the day I
> > > >moved his database to a CP/M system with a conventional FDC and a
> > > >conventional pair of 8" DSDD drives. I'd say he was in hog heaven. His
> > > >business picked up (though I don't know that the switch had anything to
> > > >do with that) and his monthly expenditure for MAALOX, Whiskey, and prune
> > > >juice was substantially reduced. Moreover, he got to see a lot more of
> > > >his wife and kids.
> > >
> > > >Until a few weeks back when I got into retrieving old 6502 source files,
> > > >I had forgotten what a piece of crap that disk subsystem was. No wondern
> > > >so many folks switched to 8" drives. I surely wish I could find an old
> > > >SVA controller ... <sigh> It's a real wonder microcomputers caught on as
> > > >well as they did, given the standard set by the Apple ][. The work WOZ
> > > >did to create the disk subsystem was really ingenious, but still orders
> > > >of magnitude less reliable than what was offered on more conventional
> > > >systems.
> > >
> > > >Dick
> > >
> > > >----- Original Message -----
> > > >From: "Fred Cisin (XenoSoft)" <cisin_at_xenosoft.com>
> > > >To: <classiccmp_at_classiccmp.org>
> > > >Sent: Tuesday, October 30, 2001 7:16 PM
> > > >Subject: Re: hard-sector 5 1/4 disk
> > >
> > > >> On Tue, 30 Oct 2001, Richard Erlacher wrote:
> > > >> > It's conceivable that the software that the Apple][ used didn't look
> for an
> > > >> > index pulse until, nominally, the "right" time, at which point it
> waited for
> > > >it,
> > > >> > then proceeded, in which case the extra holes in the index track (not
a
> > > >magnetic
> > > >> > track) would have no impact.
> > > >>
> > > >> No, it is not conceivable, since there is no light and photocell to
EVER
> > > >> EVER see the index pulse.
> > > >>
> > > >> > The format was, nevertheless, soft-sectored, thereby allowing a
smooth
> > > >> > transition from 13 sectors to 16 sectors, without a major redesign.
> > > >>
> > > >> Except that they did too much in firmware, . . .
> > > >>
> > > >>
> > >
> > > --
> > > -----------------------------------------------------------
> > > Jeffrey S. Worley
> > > Asheville, NC USA
> > > 828-6984887
> > > UberTechnoid_at_Home.com
> > > -----------------------------------------------------------
>
>
Received on Wed Oct 31 2001 - 08:40:52 GMT