Jeez... was (Re: hard-sector 5 1/4 disk)

From: Ian Koller <vze2mnvr_at_verizon.net>
Date: Wed Oct 31 01:27:06 2001

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 - 01:27:06 GMT