Use HD diskette in DD drive?

[whba...@iquest.net]

I have a 1000HX w/a 3.5" DD 720K diskette drive. Since it is hard to
find these diskettes anymore, would it be possible to just put in a HD
1.44K diskette in it, and format it to 720K using DOS 3.3? Sorry if
this has been asked before, or if it's common knowledge, but I don't
have a HD diskette to test it on.

-- Anderson, IN. USA whba...@Iquest.net 'wholly my own opinions'

Net-Tamer V 1.11X - Test Drive

[Paul Binns]

Since I was the beneficiary of the last "go-round" on
this topic, I'll let you know what we finally concluded.

3.5" DD and HD media is physically different. Though
you might be able to fool the system some of the
time, you might not be able to get away with it all the
time. This has to do with the magnetic coating formulation
on the spinning surface which is engineered to record
a lower "recording level" to prevent bleed-through
between the tracks which are naturally placed closer
together on HD disks. DD disks record at a "louder
volume". (My major over-simplification here) This
means that even if you can record files onto an HD disk,
when played back on a DD drive, the read process is
much more error prone and may be exacerbated when
that drive tries to write to the HD media.

The next major difference between HD and DD disks
is that HD disks have two square holes in the plastic
sleeve (write-protect and HD-identifier). DD disks have
only one hole.

If you take a HD disk and put it into a DD drive, then try
to format it, DOS will report "Invalid media". If you take
a HD disk and put it into an HD drive and try to format
it to DD (720k), you will get that same "Invalid media"
error message.

You can only format to DD (720k) on a PC if you are
feeding it DD disks. The reason is, of course, the second
hole.

If you take a HD disk and tape over the second hole, the
PC will format it to DD (720k). Aha !! The solution???

No, I'm afraid not. While you can get away with it for the
moment, remember that the media is also physically
different, and your disks are on a collision course with
bad sectors and data loss.

Best solution is to buy true DD (720k) disks.

DD disks are stock on-the-shelf items at The Office
Depot and similar "office supplies warehouse stores".
Many Radio Shack stores still stock them, and those
that don't will custom order them for you.

DD disks cost a little more than HDs, but that's the
reality you are faced with, I fear.

I hope this helps answer your questions sufficiently.

-=Paul=-

whba...@iquest.net wrote in message <6vjfag$b20$1...@news.iquest.net>...

[Tim Mann]

In article <6vjfag$b20$1...@news.iquest.net>, <whba...@iquest.net> wrote:
>
>I have a 1000HX w/a 3.5" DD 720K diskette drive. Since it is hard to
>find these diskettes anymore, would it be possible to just put in a HD
>1.44K diskette in it, and format it to 720K using DOS 3.3? Sorry if
>this has been asked before, or if it's common knowledge, but I don't
>have a HD diskette to test it on.

You can do that in a pinch by putting a piece of tape over the extra
hole that identifies the diskette as HD. (Actually I suppose you
wouldn't need that if you're only using the diskette in a true DD
drive with no sensor for that hole.)

However, HD and DD media have different magnetic characteristics, and
you shouldn't expect this to work well. At worst, the diskette might
not even format. At best, data life will probably be reduced, as the
media will be too strongly magnetized and you may get bleed-through of
one track or side onto the other. (So I'm told.)

--Tim
--
Tim Mann <ma...@pa.dec.com>, Compaq Systems Research Center
http://www.research.digital.com/SRC/personal/Tim_Mann/

[the TyRannoSaurus]

Hi,

Tim Mann <ma...@src.dec.com> wrote in article
<6vk7lj$t...@src-news.pa.dec.com>...

> In article <6vjfag$b20$1...@news.iquest.net>, <whba...@iquest.net> wrote:
> >
> >I have a 1000HX w/a 3.5" DD 720K diskette drive. Since it is hard to
> >find these diskettes anymore,

Hard, but not impossible. I am in a computer club, and I asked all the
members if they had any DD's left. Now I've got enough for years to come :)
Just ask around.

> >would it be possible to just put in a HD
> >1.44K diskette in it, and format it to 720K using DOS 3.3? Sorry if
> >this has been asked before, or if it's common knowledge, but I don't
> >have a HD diskette to test it on.
>
> You can do that in a pinch by putting a piece of tape over the extra
> hole that identifies the diskette as HD.

As you suggested: not necessary for a 1000HX. BUT it is necessary if you
are going to read that disk in a true AT or above. Otherwises it chokes on
such a combination: a HD disk wit a DD formatting. An IBM PS/2 does not,
however.

> However, HD and DD media have different magnetic characteristics, and
> you shouldn't expect this to work well. At worst, the diskette might
> not even format. At best, data life will probably be reduced, as the
> media will be too strongly magnetized and you may get bleed-through of
> one track or side onto the other.

Completely right. Don't jeopardise your data, get the real ones. Even
recycled DD's outperform new HD's.

> --Tim

Greetings from the TyRannoSaurus
Jan-80

[whba...@iquest.net]

On 1998-10-08 drbinns@idirect.,com said:
PB>Newsgroups: comp.sys.tandy
PB>Since I was the beneficiary of the last "go-round" on
PB>this topic, I'll let you know what we finally concluded.
PB>3.5" DD and HD media is physically different. Though

Hi, Paul. Thanks for the response.

Are you saying the problems exist *only* when trying to format a HD
diskette down to DD, *or* do HD drives *also* have a problem
reading/writing *true* DD diskettes? Because, if I can extrapolate
from your post, the HD drive would have to be able to sense that a DD
diskette was inserted, and adjust the amount of signal voltage on the
heads accordingly (besides adjusting the track widths, etc.)

This might cause a problem, because I, like many, intend to upgrade to
a different computer eventually, and I assumed I could do it by
copying the hard drive to diskettes on the HX, then loading the new
computer from those diskettes. Is that going to be a problem, since
the new computer will probably have a HD drive?

The reason this comes to mind is because of a problem I'm currently
having between 2 computers. Sometimes I go to the library, log on to
the Internet with their Pentium computer, and FTP files down to a DD
diskette (that was previously formatted on my 1000HX). Then, I take
that diskette and load it on my 1000HX. Once, I had a weird problem
with a file, so I did a chkdsk on the diskette. Here were the results:

Volume Ad created Mar 20, 1980 12:03a <-- Huh?

Errors found, F parameter not specified.
Corrections will not be written to disk.

A:\Ad
Allocation error, size adjusted.
A:\Ad
Allocation error, size adjusted.
A:\At
Allocation error, size adjusted.
A:\Ab
Allocation error, size adjusted.

730112 bytes total disk space
0 bytes in 7 hidden files <-- Huh?
702464 bytes in 13 user files
27648 bytes available on disk

Not only did it happen *that* time, but *every* time I FTP files to a
DD diskette, for later loading on my HX. Besides the allocation
errors, not only did the diskette never have a volume label, but it
shouldn't have ever had hidden files! <G> What a friggin mess! I'm
only hoping these problems only happen when trying to move files from
the Pentium *to* the HX, and not vice versa. I can't test that since
the library's computer has a pretty secure menu system that doesn't
allow me to do any experimenting.

Here's another wrinkle. Several years ago I was using a 286 (w/5.25"
HD drive) at work. For some reason, I had to initialize some
diskettes to DD. I can't remember if the diskettes were HD or if I
just needed the HD drive to properly format a *true* DD diskette. The
command was something like 'Format a: F:360' in DOS 4.01. I *do*
remember that, even though it seemed to work, I sometimes had weird
problems with the diskettes. I *also* assume one could use 'Format a:
F:720' for a 3.5" drive. If so, you wouldn't really have to tape over
the 2nd hole, like you said in your post. Sounds like an honest case
of where the MS developers tried to make a command more flexible, but
were unaware there might be a hardware problem. Otherwise, they would
never have added that parameter. The hardware people could have fixed
it by allowing the drive to apply 2 different signal levels to the
heads, and use 2 different tracking widths. Maybe some brands are
better at it than others.

After reviewing what I've written, and based on my experiences, it
seems that, in general, it might be more reliable to take a true DD
diskette written on an older computer and load it to a newer computer
with a HD drive, than any other combination.

Gawd.

Again, thanks for the response.

-- whba...@iquest.net/wbal...@netscape.net 'wholly my own opinions'