30 Oct
2001
30 Oct
'01
5:27 p.m.
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:
--
-----------------------------------------------------------
Jeffrey S. Worley
Asheville, NC USA
828-6984887
UberTechnoid(a)Home.com
-----------------------------------------------------------
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 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, . . .
>
>