31 Oct
2001
31 Oct
'01
12:40 a.m.
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(a)wxs.nl>
To: <classiccmp(a)classiccmp.org>
Sent: Wednesday, October 31, 2001 2:44 AM
Subject: Re: Jeez... was (Re: hard-sector 5 1/4 disk)
a
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
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----- Original Message -----
From: Ian Koller <vze2mnvr(a)verizon.net>
To: <classiccmp(a)classiccmp.org>rg>; <UberTechnoid(a)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(a)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(a)idcomm.com>om>, on 10/30/01
> > at 08:18 PM, "Richard Erlacher" <edick(a)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(a)xenosoft.com>
> >To: <classiccmp(a)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 > > >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(a)Home.com
> -----------------------------------------------------------