10 Jul
2019
10 Jul
'19
11:32 a.m.
BG Micro, a surplus electronics dealer I buy from sometimes, has diskettes for sale. I
don't know anything about them, but thought it may be of interest. I have no
affiliation other than being a customer on their mailing list.
Here is a link to the site:
https://www.bgmicro.com/4-pack-of-5-25-floppy-diskettes-with-sleeves.aspx
Will
10 Jul
10 Jul
12:25 p.m.
On 7/10/19 11:32 AM, Will Cooke via cctalk wrote:
They have hub rings, so they are probably 360K
6:36 p.m.
At 12:25 PM 10/07/2019 -0700, you wrote:
On 7/10/19 11:32 AM, Will Cooke via cctalk wrote:
They have hub rings, so they are probably 360K
And the index hole.
Thanks Will, this is quite fortuitous. I've just restored a HP 82901 dual 5.25"
drive,
which now runs, responds on the HP-IB bus, but I don't yet have facility to test R/W
files.
Next is to find some floppies to suit. I can't find any mention of what floppy type it
uses,
but the model specs are:
Double sided, 35 tracks/side, 16 sectors, 256 byte sectors, MFM, optical index hole
sensor.
Total capacity: Listed as 270KB, but above gives 286,720 bytes. (280KB)
So probably 360K disks would work?
I'll have a few boxes of old 360K somewhere, and digging them out was on my list for
today.
So, nice timing. Ordered about 80. No hurry, since I still don't have a suitable HP-IB
card.
Looking for a couple of cards that are PCI and listed in
http://www.hp9845.net/9845/projects/hpdir/
Pic of the drive here:
https://www.eevblog.com/forum/chat/what-did-you-buy-today-post-your-latest-…
I also have a HP 9121 (working with my HP 1630G) and 9123 (both 3.5"), looking for a
HP 9895A (8")
The origin of this project is that I have 3.5" disks with ALL the disassembler utils
for the HP 1630
logic analyzer, and want to archive them to PC (and put online, with other people waiting
for this.)
Guy
7:14 p.m.
> They have hub rings, so they are probably 360K
On Thu, 11 Jul 2019, Guy Dunphy via cctalk wrote:
And the index hole.
What about it?
There were some machines that didn't use the index (such as Apple and
Commodore), but they didn't care if there was one.
There were some that used 10 or 16 index holes ("hard sectored"). In
the unlikely event if these happen to be hard sectored, then others will
gladly take them off your hands..
Double sided, 35 tracks/side,
That would be 48 tracks per inch. Some early drives, such as the SA400
(TRS80) and SA390 (Apple) were 35 track, but later drives extended that to
40 tracks. There were a few diskettes made with a shorter window, that
could only manage 35, but otherwise 35 and 40 were the same.
16 sectors, 256 byte sectors, MFM, optical index hole
sensor.
"Hard sectored" had a single optical index hole sensor, and 10 or
16 holes
through the "cookie", with one hole through the "jacket"
On "soft sectored", there would be a "track" composed of multiple
sectors,
with headers, gaps, "sync fields", etc, to set the start and end of each
sector. We can discuss the full structure of "IBM"/"WD" track
structure
if you want.
Total capacity: Listed as 270KB, but above gives
286,720 bytes. (280KB)
So probably 360K disks would work?
Absolutely. "360K" is the name given to double sided, 40 tracks, with 9
sectors of 512 bytes per sector. The choice of using 35 tracks, with 16
sectors, and 256 bytes per sector does not squeeze as much onto the disk,
but the disk is the same.
If that machine were to have been the most popular, then those diskettes
would have been called "270K".
Single and double sided usually used the same cookie, so the difference
was solely whether the manufacturer promised/guaranteed that BOTH sides
were good. Yes, there were rumors that the manufacturer would test all of
the diskettes, adn sell the ones with 2 good sides as double sided, and on
ones with a bad side would flip them over to get the good side into place
to sell as single sided. The reality is that diskettes were never
expensive enough to be worth the labor of trying to salvage bad disks.
Except for some very early ones that had a short oval window, 35 track and
40 track were the same.
In short, . . .
the disks that YOU need are called "360K". (300 Oersted)
Do NOT use the 1.2M "high density" disks. Those are 600 Oersted, and you
need the "360K" 300 Oersted. If you try to use the "high density"
disks,
they will either FAIL, or will seem to work, but be unreadable VERY soon.
7:59 p.m.
On 7/10/19 7:14 PM, Fred Cisin via cctalk wrote:
>> They have hub rings, so they are probably 360K
To add a bit to Fred's excellent explanation, I can offer the following:
While the hub ring is *generally* a good indicator of "2D" versus
"HD"
disks, I've seen exceptions. Early 2D floppies did not use the hub ring
and I've got a few HD ones that do. The hub ring thing is a story in
itself, which I've gone into in the past.
So, basically, what matters is how the cookie is punched and what the
characteristics of the brown schmoo that it's been coated with.
High-density diskettes use a coating that contains smaller particles, is
generally thinner and of higher magnetic coercivity ("stiffer") nature.
The punching has to do with "hard" sectoring vs. "soft" sectoring.
In
the former, as Fred mentioned, there is an extra hole (in addition to
the index hole) in the cookie for each sector. Most 5.25" media is
soft-sectored. You can tell the difference by holding the jacket of a
floppy with one hand and rotating the cookie by the hub with the other.
If you only see one hole appearing through the jacket aperture with
every revolution, the disk is soft-sectored.
Beyond that, you can forget the "tracks". The same floppy can be used
in 80 track (96 track per inch) as well as 77 track (100 tracks per
inch) as well as 40 track (48 tracks per inch) drives.
5.25" diskettes are only a bit more complicated than 3.5" ones, where
you need only worry about the coating characteristics.
Having said that, there *are* oddball exceptions, but you're unlikely to
run into them in real life.
8" diskettes on the other hand, employ only one coating type, but use
the index hole to indicate single-sided, vs. double-sided and density,
as well as hard- vs. soft-sectoring and "flippy" floppies.
Again, there are the "oddball" cases, such as the Vydec floppies that
put the sector holes on the outer edge of the cookie or Memorex 650
disks that have a "dogleg" in the jacket outline, but you likely won't
run into those.
--Chuck
8:27 p.m.
On Wed, 10 Jul 2019, Chuck Guzis via cctalk wrote:
While the hub ring is *generally* a good indicator of
"2D" versus "HD"
disks, I've seen exceptions. Early 2D floppies did not use the hub ring
and I've got a few HD ones that do. The hub ring thing is a story in
itself, which I've gone into in the past.
Since you could put on hub rings yourself (there were simple jigs from
Inmac, or the deluxe version of the Berkeley Microcomputer Flip-Jig),
If there is not a hub-ring, then it is an early "360K", or it is a
"1.2M".
If there is a hub-ring, then it is a an early "360K" with DIY hub ring, or
a later "360K", or a "1.2M" with a DIY hub ring.
OR, it is one of the exceptions.
Nevertheless, going by the probabilities, if it has a hub ring, then it is
PROBABLY "360K", and if it does not have a hub ring, then it is PROBABLY
"1.2M".
So, basically, what matters is how the cookie is
punched and what the
characteristics of the brown schmoo that it's been coated with.
High-density diskettes use a coating that contains smaller particles, is
generally thinner and of higher magnetic coercivity ("stiffer") nature.
If you hold two side by side, you may see a color difference.
Beyond that, you can forget the "tracks".
The same floppy can be used
in 80 track (96 track per inch) as well as 77 track (100 tracks per
inch) as well as 40 track (48 tracks per inch) drives.
and in this example, as well as TRS80 and Apple][, the 40 track could be
35 tracks.
Having said that, there *are* oddball exceptions, but
you're unlikely to
run into them in real life.
Such as the "Twiggy" for the Apple Lisa. A high density disk with
symmetrical (extra) access slot, to help make sure that EVERY disk had
thumbprints on the cookie. If you feel a need to see one, check with Eric
Smith.
Chuck has seen a higher percentage of the oddball ones than anybody else.
The 5.25" diskette or "Mini-diskette" is bar napkin size, because Dr. Wang
said that 8" diskettes were too big. I have not been able to track down
WHICH bar.
--
Grumpy Ol' Fred cisin at xenosoft.com
9:29 p.m.
At 08:27 PM 10/07/2019 -0700, Grumpy Ol' Fred wrote:
The 5.25" diskette or "Mini-diskette" is
bar napkin size, because Dr. Wang
said that 8" diskettes were too big. I have not been able to track down
WHICH bar.
Perhaps the same bar where someone bet L Ron Hubbard that he couldn't create a
religion?
11 Jul
11 Jul
7:09 a.m.
On 7/11/19 12:29 AM, Guy Dunphy via cctalk wrote:
At 08:27 PM 10/07/2019 -0700, Grumpy Ol' Fred
wrote:
The only successful Sci Fi he ever created.
bill
The 5.25" diskette or
"Mini-diskette" is bar napkin size, because Dr. Wang
said that 8" diskettes were too big. I have not been able to track down
WHICH bar.
Perhaps the same bar where someone bet L Ron Hubbard that he couldn't create a
religion?
10 Jul
10 Jul
9:09 p.m.
At 07:14 PM 10/07/2019 -0700, you wrote:
On Thu, 11 Jul 2019, Guy Dunphy via cctalk wrote:
Because it's so long since I used any 360K floppies, that I could not
recall if some didn't have any hole. (But I did remember about the soft/hard
sectoring; 1 vs n holes.)
The 82901 specs I have don't mention if it's soft or hard sectored, but a few
diskettes I received with the drive (which are definitely for it) are single hole.
And the index hole.
What about it? There were some machines that didn't use the index
(such as Apple and
Commodore), but they didn't care if there was one.
Yes, I knew about Apple disks. http://everist.org/NobLog/20190106_hacked_appleII.htm
There were some that used 10 or 16 index holes
("hard sectored"). In
the unlikely event if these happen to be hard sectored, then others will
gladly take them off your hands..
:) Except I'm in Australia, so they could probably find them cheaper at home.
bgmicro sold at a very reasonable price. For me, most of the cost will be postage.
I send everything via shipito.com in CA (a reshipper) for consistency, tracking, and
significantly lower international rates due to their bulk deals with carriers.
Btw, I didn't deplete bgmicro's stock. They seem to mention on some items when
they
have limited stock, and they don't on the floppies. So likely have a LOT of them.
[snip]
"360K" - 300 Oersted. vs 1.2M 600 Oersted.
Can you believe that is the first time I have ever heard the actual figures for the
coatings?
I knew the 1.2M type had a higher coercivity, thus the incompatibility. Ditto with
3.5" 720K
vs 1.44M.
Thanks for the detailed review, and thanks to the others adding more. Saved.
Guy
10:40 p.m.
> "360K" - 300 Oersted. vs 1.2M 600
Oersted.
On Thu, 11 Jul 2019, Guy Dunphy wrote:
Can you believe that is the first time I have ever
heard the actual figures for the coatings?
I knew the 1.2M type had a higher coercivity, thus the incompatibility. Ditto with
3.5" 720K
vs 1.44M.
Then add to the useless information:
"720K" diskettes ("micro-diskettes") are 600 Oersted.
"1.4M" diskettes are 720 - 750 Oersted. Notice that it is not as much
difference between them as there is between the 5.25 variants. Therefore,
using a "720K" diskette for "1.4M" or vice-versa, while less reliable,
is
something that you might "GET AWAY WITH". There were punches being
peddled for doing so! You could take a good quality "720K" diskette and
turn it into a mediocre/flaky "1.4M"
BTW, if you multiply out the space on it (2 sides * 80 tracks per side *
18 sectors per track * 512 bytes per sector), 1474560, the only way that
you can get 1.44 as the number of MBs is if you creatively redefine MB to
be 1,024,000 (1000K, 1000* 1024, 2^10 * 10^3)
A MebiByte is 1048576 or 2^20. A "1.4M" disk is 1.40625 MebiBytes.
BTW, ANOTHER incompatability between "360K" and "1.2M" was 48 tracks
per
inch V 96 tracks per inch. ROUNDING THE NUMBERS (researching the correct
numbers,and redoing the calculations ACCURATELY is "left as an exercise
for the reader"),
a "360K" has tracks that are about 1/2mm spacing, that are about 1/3mm width.
96tpi is about 1/4mm spacing, with width about 1/6mm.
A 1.2M drive can read 360K by double-stepping. No problem.
If it also adjusts the write current, then it can format a virgin 360K
disk. The tracks will be sub-standard width, but will work. (1/6mm wide
tracks with 1/2mm spacing)
HOWEVER, if you take a track that has been written to on a 360K drive, the
1.2M drive, when it RE-writes that track will not erase the full width of
the old 360K track. You will have a 1/6mm track down the middle
of a 1/3mm track.
The result is a "360K" track that still reads just fine on
the 1.2M drive, but is not readable [reliably] on a 360K drive.
Visualize a car tiretrack that has been followed by a motorcycle. Two
motorcycles can leave a pair of tracks that resemble car tracks if they
are the only tracks. But, if there is already a car's tracks, the
motorcycles won't fully replace the car's tracks.
--
Grumpy Ol' Fred cisin at xenosoft.com
11 Jul
11 Jul
1:47 p.m.
On 7/10/19 11:32 AM, Will Cooke via cctalk wrote:
They have hub rings, so they are probably 360K
Weren't these 89 cents when this was first posted? Well they're $1.89 now.
You're altering the market!
7:10 a.m.
On 7/10/19 2:32 PM, Will Cooke via cctalk wrote:
BG Micro, a surplus electronics dealer I buy from
sometimes, has diskettes for sale. I don't know anything about them, but thought it
may be of interest. I have no affiliation other than being a customer on their mailing
list.
Here is a link to the site:
https://www.bgmicro.com/4-pack-of-5-25-floppy-diskettes-with-sleeves.aspx
Will
That's not the same BG Micro we bought stuff from in the
early 80's, is it?
bill
8:27 a.m.
On July 11, 2019 at 9:10 AM Bill Gunshannon via cctalk
<cctalk at classiccmp.org> wrote:
On 7/10/19 2:32 PM, Will Cooke via cctalk wrote:
The one with the yellow photocopied catalog? That's the same one.
The owner/founder passed away a year or two ago and I believe his daughter is running it
now.
Will
"A designer knows he has achieved perfection not when there is nothing left to add,
but when there is nothing left to take away." --? Antoine de Saint-Exupery
"The names of global variables should start with? ? // "? --?https://isocpp.org
BG Micro, a surplus electronics dealer I buy from
sometimes, has diskettes for sale. I don't know anything about them, but thought it
may be of interest. I have no affiliation other than being a customer on their mailing
list.
Here is a link to the site:
https://www.bgmicro.com/4-pack-of-5-25-floppy-diskettes-with-sleeves.aspx
Will
That's not the same BG Micro we bought stuff from in the
early 80's, is it?
bill
1990
days inactive
1991
days old
12 comments
7 participants
participants (7)
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aek＠bitsavers.org -
bill.gunshannon＠hotmail.com -
cclist＠sydex.com -
cisin＠xenosoft.com -
guykd＠optusnet.com.au -
silent700＠gmail.com -
wrcooke＠wrcooke.net