Re: Good source for "new" 5.25 and 3.5 inch floppy disks?
- From: "Michael J. Mahon" <mjmahon@xxxxxxx>
- Date: Mon, 01 Oct 2007 12:06:40 -0700
SlickRCBD wrote:
Michael J. Mahon wrote:
glen herrmannsfeldt wrote:Just to throw my 2-cents in, My personal experience was the the following. Note that I never owned a 5.25" HD drive.
Michael J. Mahon wrote:
(snip)
If you're not sure, and you care about the permanence of your data,
HD media in DD 3.5" drives should be avoided.
As far as I understand it, it either will or won't write.
There is a very small probability of a partial write,
somewhat similar to a coin flip landing on the side.
The coercivity specifies the field strength necessary to switch the
media from one saturated state to another.
If the media was previously recorded, then you are correct--the media,
or at least substantial parts of it, are already saturated in one or
the other direction, and write current will either be sufficient to
change it or not.
However, if the media is not recorded, or has been degaussed, then
smaller write currents will be sufficient to cause a partial response
and leave the media in a lower state of magnetization. In this case,
the disk could read correctly for a while, but would have a lower
read signal and a lower threshold for data disturbance.
As noted before, a DD 5.25" drive will *not* reliably write HD media.
With a factor of two in coercivity for 5.25in it is pretty much
zero chance. Note that core memory depends on half the current not
writing a bit for every write or read cycle.
Excellent point!
HD 5.25" disk in an AppleDisk 5.25" drive:
Would NOT format without errors, would not read or write data.
HD 3.5" disk in an AE 3.5" 800K drive (Replaced my AppleDisk 3.5 over a year before I tried a HD disk)
Formatted, but kept giving errors when I tried to use it. The disk formatted just fine in the computers at school, and I also tested it on a friend's PC.
A PC (or other HD) drive would saturate the media, but it sounds like
your AE drive was not saturating it, leaving it partially magnetized.
After I finally got my hands on a SuperDrive, I tried drilling holes in a DD disk and formatting it as HD. It seemed to work fine, but as time went on I noticed that these disks seemed to have a much much higher rate of failure. It has been over 8 years since I've done this, and I don't think any of the drilled disks are still working. Of course, I've got a bunch I haven't tested in a while either, but none of the ones I've tried have worked perfectly. It seems to somehow damage the disk and reformatting doesn't help.
Degaussing and reformatting would probably put you back where you
started.
That's my non-technical, personal experience as best as I can remember it. It's what most people care about, what works and what doesn't. I should note that it took sevearl months for a DD disk formatted as HD to develope problems. Months of regular use, such as the data disk I used for my classes at school.
That's consistent with the behavior of a lower coercivity medium used
at a high density.
As the oppositely magnetized regions get closer together, they have
more tendency to "flip" adjacent regions. Higher coercivity prevents
this (at the cost of being harder to write).
Bottom line: there's a reason for most specifications. ;-)
(But not all--for example, after the early 1980s, virtually all
"single-sided" media were actually suitable as "double-sided".)
-michael
NadaPong: Network game demo for Apple II computers!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it's seriously underused."
.
- References:
- Re: Good source for "new" 5.25 and 3.5 inch floppy disks?
- From: SlickRCBD
- Re: Good source for "new" 5.25 and 3.5 inch floppy disks?
- Prev by Date: Re: ADTPro question or idea
- Next by Date: Re: ADTPro question or idea
- Previous by thread: Re: Good source for "new" 5.25 and 3.5 inch floppy disks?
- Next by thread: Re: Good source for "new" 5.25 and 3.5 inch floppy disks?
- Index(es):
Relevant Pages
|
