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 - 03:44:49 GMT