Fragility of 5.25" Diskettes

[bond007clone]

Hi,

I've got a bunch of old 5.25" diskettes and I've got a few questions
about the fragility of them.

I know that if you touch the magnetic part of the disk while it's out
of the sleeve with your finger or something, you've just screwed the
disk. However, what if the magnetic part of the disk is touched while
it's still in the sleeve? Does that harm it as well?

On some 5.25" disks, there is a small hole next to the big hole. Is
this used to write to the disk, or?

What can one do to preserve the lifetime of 5.25" disks?

Thanks in advance!!

 

[Anton Ertl]

Hi,

I've got a bunch of old 5.25" diskettes and I've got a few questions
about the fragility of them.

I know that if you touch the magnetic part of the disk while it's out
of the sleeve with your finger or something, you've just screwed the
disk. However, what if the magnetic part of the disk is touched while
it's still in the sleeve? Does that harm it as well?

You mean, you press the sleeve onto the disk? Probably not as bad,
but still not a good idea. Also beware of too much pressure on the
disks. I have lost several 3.5" disks by transporting them in a way
that pressed the enclosure onto the disk; then I bought a hard case
for them.

On some 5.25" disks, there is a small hole next to the big hole. Is
this used to write to the disk, or?

The small hole near the center is there for hard-sectoring, and AFAIK
was never used by mass-market drives. If you turn the disk, you will
notice that there is a hole in it; AFAIK with hard-sectoring this hole
was recognized optically, and indicated the start of the first sector;
supposedly there were also disks with 16 holes, where each hole
indicated the start of another sector, but I never saw one.

What can one do to preserve the lifetime of 5.25" disks?

Keep it cool and dry. I would recommend getting the data off the
floppy while you can and putting it on something that you backup
regularly.

- anton

 

[Rod Speed]

(e-mail address removed) wrote

I've got a bunch of old 5.25" diskettes and I've
got a few questions about the fragility of them.

I know that if you touch the magnetic part of the disk while it's out of
the sleeve with your finger or something, you've just screwed the disk.
However, what if the magnetic part of the disk is touched while
it's still in the sleeve? Does that harm it as well?

Nope. The problem is getting finger prints on the magnetic surface.

On some 5.25" disks, there is a small hole next to
the big hole. Is this used to write to the disk, or?

It lets the drive work out where the disk has rotated to before its been
formatted.

What can one do to preserve the lifetime of 5.25" disks?

Basically keep the dust etc off it and dont store them where its
humid. You can get mold growing on them in the worst humidity.

 

[Arno Wagner]

Hi,

I've got a bunch of old 5.25" diskettes and I've got a few questions
about the fragility of them.

I know that if you touch the magnetic part of the disk while it's out
of the sleeve with your finger or something, you've just screwed the
disk. However, what if the magnetic part of the disk is touched while
it's still in the sleeve? Does that harm it as well?

The blank part visible in the large opening: Yes, just as bad. However
if you have disks screwed that way, thay can be cleaned, since the
problem is skin-fat. I would expect that mild soap and water applied
with a soft cloth or very soft tissue should make the disks usable
(for immediate data transfer to a clean medium!) enough to be readable
and not dmage the drive (FDDs have direct surface-head contact). If
you attempt this, you need to remove the disk from its sleeve and need
to use clean gloves. My guess is that latex gloves should be suitable
if you wash them carefully (while wearing them) before.

On some 5.25" disks, there is a small hole next to the big hole. Is
this used to write to the disk, or?

No. It is the index hole. Used to determine where the tracks start.
There is a matching hole in the disk itself that is visible
through thye hole in the sleeve once ber revolution.

What can one do to preserve the lifetime of 5.25" disks?

Copy them to image files and store the image files on more reliable
medium (professional tape, multiple HDDs, multiple memory-sticks, MOD
or DVD-RAM, stay away from CD/DVD). Then if you need them again,
freshly format a 5.25" disk and write the image to it.

The biggest risk is that the magnetisation degrades over time. That
does not kill the disk, it can just be re-formated. But it kills the
data on the disk. I copied all my old Atari 3.5" disks to image files
some time ago and found that after 5 years about 1/3 of them were
unreadable or only partially readable.

Arno

 

[Arno Wagner]

Hi, [...]
On some 5.25" disks, there is a small hole next to the big hole. Is
this used to write to the disk, or?

The small hole near the center is there for hard-sectoring, and AFAIK
was never used by mass-market drives.

Actually hard-sectoring has a series of holes on the disk. That was
used in some 8" disks. I saw some really old ones that had them a long
time ago. For 5.25" it is only one hole for the track start and it is
used by all 5.25" drives and even 3.5" drives (different mechanism
there, but same signal, called "index"). The floppy controller if
free to put different numbers and sizes of sectors on these disks
during formatting. It must put the first sector in a specific position
relative to the start-of-track marker. With hard-sectoring, the sector
positions and number is fixed and dictated by the disk.

Arno

 

[Anton Ertl]

For 5.25" it is only one hole for the track start and it is
used by all 5.25" drives

It is obviously not used on drives where the disks could be flipped
(like the Commodore 1541 drive). I guess there were some single-sided
drives that used the index hole and could not use flipped discs
(without punching an additional index hole in the sleeve), but
probably only early in time. And if the single-sided drives did not
use the index hole, I doubt that the double-sided drives did.

Thanks for the other corrections.

- anton

 

[Arno Wagner]

It is obviously not used on drives where the disks could be flipped
(like the Commodore 1541 drive). I guess there were some single-sided
drives that used the index hole and could not use flipped discs
(without punching an additional index hole in the sleeve), but
probably only early in time. And if the single-sided drives did not
use the index hole, I doubt that the double-sided drives did.

Actually the C64 was an exception and did not use a standard
floppy controller chip. A standard floppy controller chip does
require the index signal, otherwise it does not work. You
cannot flip 5.25" disks in a standard (PC) floppy.

Arno

 

[Guest]

AE [Thu, 29 Dec 2005 21:52:43 GMT]:

The small hole near the center is there for hard-sectoring, and AFAIK

Nah. Hard sectors would have 8 or 9 holes, or as
many as there are sectors per track. One hole
(soft sector) is there because it has to be.

supposedly there were also disks with 16 holes, where each hole
indicated the start of another sector, but I never saw one.

They were before your time, as much as you
not seeing may make that seem impossible (o).

 

[Rod Speed]

Actually hard-sectoring has a series of holes
on the disk. That was used in some 8" disks.

It was used on some 5.25" floppys too.

I saw some really old ones that had them a long time ago.

I used them for years and years and still have some.

For 5.25" it is only one hole for the track
start and it is used by all 5.25" drives
Nope.

and even 3.5" drives (different mechanism there, but same
signal, called "index"). The floppy controller if free to put
different numbers and sizes of sectors on these disks during
formatting. It must put the first sector in a specific position
relative to the start-of-track marker. With hard-sectoring, the
sector positions and number is fixed and dictated by the disk.

And was seen with some 5.25" floppys.

 

[Antoine Leca]

En Anton Ertl va escriure:

It is obviously not used on drives where the disks could be flipped
(like the Commodore 1541 drive).

This is comp.sys.*ibm.pc*.hardware.storage so one can guess we are talking
about floppies dealt with the NEC 765 controller or clones. At least unless
you make duely marked exceptions.

I guess there were some single-sided drives that used the index
hole and could not use flipped discs (without punching an
additional index hole in the sleeve), but probably only early in
time.

I know some very early PCs had single-sided floppy drives, but they
disappeared early; I cannot say if it was doable to flip disks with them;
probably not worth the trouble for PCs.
I certainly never see a 5½ floppy intended for PC with two holes in the
sleeve (but I did for others machines; perhaps Apple ][; not sure, it has
been a long time).

And if the single-sided drives did not use the index hole,
I doubt that the double-sided drives did.

The double sided drive has two heads, one above and another below the disk.
Compared to flipped disk, the magnetic stream is reversed. The optical
detection of the index is only in one place, and serves for both sides at
the same time.


Antoine

 

[J. Clarke]

Hi,

I've got a bunch of old 5.25" diskettes and I've got a few questions
about the fragility of them.

They are a good deal less fragile than is commonly believed--the higher
density of course are more so than the lower.

I know that if you touch the magnetic part of the disk while it's out
of the sleeve with your finger or something, you've just screwed the
disk.

Not necessarily--over the long term acids from skin oil will do bad things
to it but short term it should still be readable unless you were grimy
enough to abrade the surface.

However, what if the magnetic part of the disk is touched while
it's still in the sleeve? Does that harm it as well?

No. Not unless you press hard enough to put a discernible divot in the
disk. Even then sometimes it can be resurrected--hold it over a 150 watt
incandescent light bulb until the divot goes away and you may be able to
recover the data (done that more than once).

On some 5.25" disks, there is a small hole next to the big hole. Is
this used to write to the disk, or?

Index holes--those would be hard sectored disks.

What can one do to preserve the lifetime of 5.25" disks?

Copy them to another type of media.

 

[Antoine Leca]

En "hel" va escriure:

Hard sectors would have 8 or 9 holes

9 holes is harly likely (for engineering reasons).

I do not know if it is the reason why the classical 5½" PC floppies came
first as 160/320 KB (8-sector, to be "compatible" with the hard sectoring
"standards") and then grew up to 180/360 KB (9-sector), though.


Antoine

 

[Rod Speed]

hel wrote

9 holes is harly likely (for engineering reasons).

Wrong, that is precisely what was used.

I do not know if it is the reason why the classical 5½" PC floppies
came first as 160/320 KB (8-sector, to be "compatible" with the hard
sectoring "standards") and then grew up to 180/360 KB (9-sector), though.

It had nothing to do with compatibility which didnt exist.

The initial formats were essentially determined by that the ic could do.

 

[Antoine Leca]

In news:[email protected], Rod Speed va escriure:

Wrong, that is precisely what was used.

I read about 10+1 holes and 16+1 holes (including the index supplementary
one that I forgot) as being the most used ones for 5¾". The idea being that
hard sectoring allow more precise synchronisation of the start of each
sector, so a higher number of sectors, or twice as much sectors of
half-number of bytes.

What do you mean for "what was used": 8+1 (so 160 KB/side in double density
with 512 bytes/sector), or 9+1 (180KB/side)?
I thought the latter (implying 40° angles) was difficult to design, at punch
time.


Of course, PCs used soft-sectoring, normally with 8 (early) then 9 (usual)
sectors/track.


Antoine

 

[Rod Speed]

In news:[email protected], Rod Speed va escriure:

I read about 10+1 holes and 16+1 holes (including the index
supplementary one that I forgot) as being the most used ones for 5¾".
The idea being that hard sectoring allow more precise synchronisation
of the start of each sector, so a higher number of sectors, or twice
as much sectors of half-number of bytes.

What do you mean for "what was used": 8+1 (so 160 KB/side
in double density with 512 bytes/sector), or 9+1 (180KB/side)?
I thought the latter (implying 40° angles) was difficult to design,
at punch time.

Cant see why. The system isnt that accurate given that
its an optical sensor. There isnt any particular problem
with punching the hole in the right place with 40°.

Of course, PCs used soft-sectoring, normally
with 8 (early) then 9 (usual) sectors/track.

Sure.

 

[Antoine Leca]

In news:[email protected], Rod Speed va escriure:

Cant see why.

It is geometrically difficult to divide an angle into 3 parts.
In fact, it is not difficult, but it requires an intermediary measure, which
adds to the overall imprecision.

The system isnt that accurate given that its an optical sensor.

Sure, but I guess the tolerance on angles would not be very wide either.
Particularly since the very point of hard sectoring is to enhance density,
and those holes are the very path for it.


Antoine

 

[Arno Wagner]

In news:[email protected], Rod Speed va escriure:

It is geometrically difficult to divide an angle into 3 parts.
In fact, it is not difficult, but it requires an intermediary measure, which
adds to the overall imprecision.

Not an issue at all. The issue is more that FDD controller chips
were not fast enough in the beginning to switch from one sector to
the next in the time they have with 9 sectors with 512 Bytes each.

Huh? Optical sensors can be _very_ precise.

Sure, but I guess the tolerance on angles would not be very wide
either. Particularly since the very point of hard sectoring is to
enhance density, and those holes are the very path for it.

The very point of hard sectoring in floppies is to make the
contoller electronics simpler. No other point.

Arno

 

[J. Clarke]

In news:[email protected], Rod Speed va escriure:

It is geometrically difficult to divide an angle into 3 parts.
In fact, it is not difficult, but it requires an intermediary measure,
which adds to the overall imprecision.

However a machinist doesn't usually do it by geometric layout, he just
cranks the indexing table around to 0, 120, 240. Gives him the same
accuracy as if he was making 4 holes at 0, 90, 180, 270. Probably has
detents in all those positions.

Sure, but I guess the tolerance on angles would not be very wide either.
Particularly since the very point of hard sectoring is to enhance density,
and those holes are the very path for it.

A typical Harbor Freight (among machinists this is pretty much the
definition of crap) rotary positioning table is _marked_ in increments of
less than .003 degree (specifically in tenths of a second of arc) and can
be repeatably positioned to about half that even by me--a good machinist
could get better than .001 degree resolution out of it. If a disk has 9
sectors and 512 bytes per sector, the width of a bit is about .01 degree,
or ten times as wide as what even a crappy indexing table in the hands of a
rank amateur can do. Seems to me then that even a cheap indexing table
could position the holes with sufficient accuracy. In the real world there
would be a purpose-made machine cutting all 9 holes simultaneously, and
that machine would be made using tools considerably better than those that
can be obtained from Harbor Freight which means that considerably higher
accuracy than that can be achieved.

 

[Rod Speed]

Rod Speed wrote

It is geometrically difficult to divide an angle into 3 parts.
In fact, it is not difficult, but it requires an intermediary
measure, which adds to the overall imprecision.

Thats a myth, 40° is no harder to handle
at manufacturing time than say 45°

Sure, but I guess the tolerance on angles would not be very wide either.

Cant see any important difference between say 40° and 45°

Particularly since the very point of hard sectoring is to enhance density,

No it isnt, it just simplifys the controller.

and those holes are the very path for it.

What matters is how reproducible the indexing is. I cant see there is any
important difference between say 40° and 45° with an optical sensor.