26 Mar
2000
26 Mar
'00
2:36 a.m.
Are you using a 1.2MB floppy drive to write a 360K
floppy disk?
Yes, but I used the drive (1.2Mb) to format it to 360K.
____________________________________________________________
David Vohs, Digital Archaeologist & Computer Historian.
Computer Collection:
"Triumph": Commodore 64C, 1802, 1541, FSD-1, GeoRAM 512, Okimate 20.
"Leela": Macintosh 128 (Plus upgrade), Nova SCSI HDD, Imagewriter II.
"Delorean": TI-99/4A.
"Monolith": Apple Macintosh Portable.
"Spectrum": Tandy Color Computer 3.
"Boombox": Sharp PC-7000.
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26 Mar
26 Mar
3:08 a.m.
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3:33 a.m.
It doesn't matter whether the diskette is a 1.2 MB one or a 360K type, but
the drive which wrote it make a great deal of difference. 1.2 MB drives can
read 360k diskettes just fine, but you can't expect a drive designed to
operate on half the track width (twice the density) and even more bit
density, to erase the writing of a 48 TPI 360K drive properly. It works OK
the first time, and less well the second ... and so on until it fails
because the residue left behind by the 48tpi drive generates too much noise
for the 96 tpi drive to discriminate between noise and signal.
Dick
----- Original Message -----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, March 26, 2000 10:08 AM
Subject: Re: Parallel port hard drives?
Did you start with a bulk-erased (i.e. with a degausser) disk? And is it
a real 360K disk (and not a 1.2Mbyte one)?
-tony
Are you using a 1.2MB floppy drive to write a 360K
floppy disk?
Yes, but I used the drive (1.2Mb) to format it to 360K. 
6:16 a.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
It doesn't matter whether the diskette is a 1.2 MB
one or a 360K type, but
Give us a break! YOU know better!
YES, IT WILL MATTER!
And it is NOT necessary for any idiot to say, "But I use the wrong type of
diskettes all the time."
360K is 300 Oerstedt. 1.2M is 600 Oerstedt.
My personal experience is that using a 600 Eorstedt diskette in a 300
Oerstedt application results in a significantly reduced lifetime for the
data. Sometimes minutes!
the drive which wrote it make a great deal of
difference. 1.2 MB drives can
read 360k diskettes just fine, but you can't expect a drive designed to
operate on half the track width (twice the density) and even more bit
density, to erase the writing of a 48 TPI 360K drive properly. It works OK
the first time, and less well the second ... and so on until it fails
because the residue left behind by the 48tpi drive generates too much noise
for the 96 tpi drive to discriminate between noise and signal.
If you HAVE to use a 1.2M drive to write 360K diskettes, it is best to
start with a virgin disk. And ALWAYS bulk erase it (preferably with a
better bulk eraser than the one on your refrigerator door). THEN format
it as 360K ("/4" in DOS). If the diskette is EVER written to by a 360K
drive (even "ERASE"ing a file), then bulk erase and FORMAT in the 1.2M
drive again.
You have to take these steps if you want reliable writes to 360K in a 1.2M
drive, even if you might sometimes get away with not doing it right.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
7:39 a.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
I remember a discussion on the Beginners/????? area on Prodigy many years
ago when I had a discussion with an "expert" who argued it didn't make any
difference. It really didn't matter to me, but the beginners who took that
sad advice could well have problems and never know why. Hence I did argue
the point, fruitlessly I might add, and of course, I knew this was one
"expert" whose advice on anything was suspect.
"Fred Cisin (XenoSoft)" wrote:
It doesn't matter whether the diskette is a
1.2 MB one or a 360K type, but
Give us a break! YOU know better!
YES, IT WILL MATTER!
And it is NOT necessary for any idiot to say, "But I use the wrong type of
diskettes all the time."
360K is 300 Oerstedt. 1.2M is 600 Oerstedt.
My personal experience is that using a 600 Eorstedt diskette in a 300
Oerstedt application results in a significantly reduced lifetime for the
data. Sometimes minutes!
the drive which wrote it make a great deal of
difference. 1.2 MB drives can
read 360k diskettes just fine, but you can't expect a drive designed to
operate on half the track width (twice the density) and even more bit
density, to erase the writing of a 48 TPI 360K drive properly. It works OK
the first time, and less well the second ... and so on until it fails
because the residue left behind by the 48tpi drive generates too much noise
for the 96 tpi drive to discriminate between noise and signal.
If you HAVE to use a 1.2M drive to write 360K diskettes, it is best to
start with a virgin disk. And ALWAYS bulk erase it (preferably with a
better bulk eraser than the one on your refrigerator door). THEN format
it as 360K ("/4" in DOS). If the diskette is EVER written to by a 360K
drive (even "ERASE"ing a file), then bulk erase and FORMAT in the 1.2M
drive again.
You have to take these steps if you want reliable writes to 360K in a 1.2M
drive, even if you might sometimes get away with not doing it right.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
9:16 a.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
I'm not sure I am the one who should wake up here. I would repeat "It
doesn't matter whether the diskette is a 1.2 MB one or a 360K type" but it
does depend what sort of drive it is. The Coercivity of the media will
effect signal level in both reads and writes, but won't make up for the fact
that the heads designed for 48tpi will write a significantly wider swath on
the diskette than the 96tpi drive can erase. Consequently, and I'll bet
you've had this experience, you can format a bulk erased diskette to 48tpi
with a 96 TPI drive and have it work for a while.
The more the diskette is written, by the 48tpi drive, the harder it becomes
for the 96tpi drive to erase its writing, and, of course, the 48TPI drive
will have the most trouble because the signal not erased in the 96tpi drive
is perceived by the 48tpi drive as noise, while the signal written by the
96tpi is written at a lower level to begin with, since the drive relies on
the higher coercivity of the medium to generate a larger signal amplitude if
that factor is to come into play at all.
Under worst-case conditions the signal is written to the inner tracks by the
96tpi drive, which attenuates write current on the inner tracks, and it is
read by the 48TPI drive. The diskette was a bulk erased diskette and was
formatted in the 96 tpi drive. The region of the diskette that we're using
was written by the 48tpi drive and subsequently the new data was written in
the 96TPI drive.
Clearly, there is a risk that the 48tpi drive won't be able to distinguish
the narrow channel of cleanly written data from the 96tpi drive, among the
straddling field of residual signal at nominally the same frequency but out
of phase with the sync field, address mark, data, and CRC written by the
96tpi drive. Consequently there's a real risk that there will be a data CRC
error if not an address mark misread.
Remember, in order to get the drive to perform properly at 96TPI, the head
gaps had to be made narrow enough to avoid interference between adjacent
tracks. This was accomplished by a combination of changes in head
design/manufacture, write current levels, and read amplifier gain. I submit
that it's the heads that make the difference that we normal mortals perceive
as "not working" when the 360K drive can't read the 96tpi's writing.
The
signal to noise ratio is MUCH to low.
Dick
----- Original Message -----
From: Fred Cisin (XenoSoft) <cisin(a)xenosoft.com>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, March 26, 2000 1:16 PM
Subject: 360K in a 1.2M drive (was: Parallel port hard drives?
> It doesn't matter whether the diskette is a
1.2 MB one or a 360K type,
but
Give us a break! YOU know better!
YES, IT WILL MATTER!
And it is NOT necessary for any idiot to say, "But I use the wrong type of
diskettes all the time."
360K is 300 Oerstedt. 1.2M is 600 Oerstedt.
My personal experience is that using a 600 Eorstedt diskette in a 300
Oerstedt application results in a significantly reduced lifetime for the
data. Sometimes minutes!
> the drive which wrote it make a great deal of difference. 1.2 MB drives
can
> read 360k diskettes just fine, but you can't
expect a drive designed to
> operate on half the track width (twice the density) and even more bit
> density, to erase the writing of a 48 TPI 360K drive properly. It works
OK
> the first time, and less well the second ... and
so on until it fails
> because the residue left behind by the 48tpi drive generates too much
noise
for the 96 tpi
drive to discriminate between noise and signal.
If you HAVE to use a 1.2M drive to write 360K diskettes, it is best to
start with a virgin disk. And ALWAYS bulk erase it (preferably with a
better bulk eraser than the one on your refrigerator door). THEN format
it as 360K ("/4" in DOS). If the diskette is EVER written to by a 360K
drive (even "ERASE"ing a file), then bulk erase and FORMAT in the 1.2M
drive again.
You have to take these steps if you want reliable writes to 360K in a 1.2M drive, even if you might sometimes get away with not
doing it right.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
9:36 a.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
This is only part of the story
The 1.2 Mb floppies are written with a lower write current than the
360 Kb. Since the magnetic quality of the former type is stronger and the
tracks are smaller and closer this will prevent crossover effects between
the tracks.
In certain situations it may be desirable to attempt a datatransfer
between different drive systems. Then a repeated formatting of
a bulkereased or brandnew unformatted 360Kb floppy written with a
1.2 Drive may do the trick. You will also have to write the data
repeatedly. This may only work over hours or days rather than month or
years.
Sipke de Wal
----- Original Message -----
From: Fred Cisin (XenoSoft) <cisin(a)xenosoft.com>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, March 26, 2000 10:16 PM
Subject: 360K in a 1.2M drive (was: Parallel port hard drives?
> It doesn't matter whether the diskette is a
1.2 MB one or a 360K type,
but
Give us a break! YOU know better!
YES, IT WILL MATTER!
And it is NOT necessary for any idiot to say, "But I use the wrong type of
diskettes all the time."
360K is 300 Oerstedt. 1.2M is 600 Oerstedt.
My personal experience is that using a 600 Eorstedt diskette in a 300
Oerstedt application results in a significantly reduced lifetime for the
data. Sometimes minutes!
> the drive which wrote it make a great deal of difference. 1.2 MB drives
can
> read 360k diskettes just fine, but you can't
expect a drive designed to
> operate on half the track width (twice the density) and even more bit
> density, to erase the writing of a 48 TPI 360K drive properly. It works
OK
> the first time, and less well the second ... and
so on until it fails
> because the residue left behind by the 48tpi drive generates too much
noise
for the 96 tpi
drive to discriminate between noise and signal.
If you HAVE to use a 1.2M drive to write 360K diskettes, it is best to
start with a virgin disk. And ALWAYS bulk erase it (preferably with a
better bulk eraser than the one on your refrigerator door). THEN format
it as 360K ("/4" in DOS). If the diskette is EVER written to by a 360K
drive (even "ERASE"ing a file), then bulk erase and FORMAT in the 1.2M
drive again.
You have to take these steps if you want reliable writes to 360K in a 1.2M
drive, even if you might sometimes get away with not doing it right.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
1:12 p.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
There are TWO problems.
The disk matters.
The drive matters.
360K is 300 Oerstedt. 1.2M is 600 Oerstedt.
Using the wrong coercivity of diskette, you will NEVER get a good,
reliable result. You MIGHT sometimes almost get away with using the
worng diskette. SOME idiots will claim that they "always use the wrong
diskette". WHY???
BTW, 720K and 1.4M are nominally 600 Oerstedt and 750 Oerstedt, which is
close enough that "getting away with" is a MUCH more likely proposition.
There are several problems with using the wrong drive. But some times
there isn't an adequate alternative.
Read/write currrent level:
With the exception of some of the preproduction Mitsubishi 4854 and
prototype Shugart 475s, all of the 1.2M drives have explicit provision for
TWO read/write current levels, explicitly for the purpose of permitting
reading, and even writing, 360K diskettes in the 1.2M drives. That is
typically NOT where the problem arises.
Motor speed:
8" is at 360RPM; 1.2M is at 360RPM 360K is at 300RPM
To do 360K in a 1.2M drive typically requires that the controller
compensate for the different motor speed by running the 360K data transfer
rate at 300Kbps instead of the usual 250K bps. PC controllers can
normally handle that. Hooking a 1.2M drive to a non-PC controller that
expects an 8" drive will not provide for that, and therefore will not work
right for trying to do 360K diskettes.
Many current drives have dual spindle speeds (300, 360)
Weltec once made a 180RPM drive that would permit a PC 360K controller to
do 1.2M diskettes! (reliability was less than ideal)
THAT is typically not where the problem lies.
Track width:
Track width is a problem. Not only with 1.2m drives and 360K diskettes,
but also even with 720K/800K 5.25" drives (Shugart 465, Tandon TM100-4,
etc.) with 360K disk formats.
360K is about 1/2 mm per track, and the actual track itself is about 1/3mm
wide.
1.2M, 720K 5.25", etc. is about 1/4mm per track, and the actual track
itself is about 1/6mm wide.
When working with a virgin, bulk-erased 300 Oerstedt diskette, the 1.2m
(or 720K 5.25") drive CAN produce a diskette using every other track, that
is ALMOST acceptable. It will have tracks that are only 1/6mm wide, but
properly spaced at 1/2mm increments. You normally CAN get away with that,
unless/until:
if you EVER write to THAT diskette with a 360K drive, even "just erasing a
file", you will have replaced that 1/6mm wide sector with a 1/3mm wide
sector. From that point on, the diskette should NOT ever be written to
with the 1.2m drive, unless/until it has been bulk-erased and formatted
again.
A 96TPI drive can NOT do an acceptable job of REformatting or REwriting
over a 1/3mm wide track! Some people, using SOME drives have found that
it is ALMOST good enough, and can sometimes get away with it. But that's
like trying to use MY car at 100 mph. It just isn't built to do it RIGHT.
Therefore, it IS possible to do an emergency transfer diskette from 1.2M
to 360K, using a 300 Oerstedt diskette. But repeated back and forth
requires careful attention to detail to avoid ever trying to rewrite a
1/3mm wide track with the 1.2M drive.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
4:24 p.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
I'm in agreement, pretty much with what's been said here. Please see
embedded comments below.
Dick
----- Original Message -----
From: Fred Cisin (XenoSoft) <cisin(a)xenosoft.com>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, March 26, 2000 8:12 PM
Subject: Re: 360K in a 1.2M drive (was: Parallel port hard drives?
There are TWO problems.
The disk matters.
The drive matters.
360K is 300 Oerstedt. 1.2M is 600 Oerstedt.
Yes, but, given that the goal is to write a 48TPI 360K diskette, the
coercivity will be the same, since the media are the same. It's worth
considering that toward the "maturity" of the 5.25" technology, the media
available throughtout the market were really pretty much the same, and the
drives were pretty similar too, except for the differences essential to
maintaining their functionality. After the "new" had worn off the 1.2MB
technology, drive makers started migrating the new technology onto the
"standard" line of products because they could sell more. Once production
was in full swing it was a better practice to put the same electronics and
heads onto all their drives instead of maintaining various technologies.
Each step of the way created confusion in the market. Eventually the
technology was abaondoned for the superior 3.5" drives. Nevertheless, the
media need not be considered for purposes of THIS discussion because the
target medium is the 300-Oerstedt 48TPI 5.25" diskette. The issue was that
the old 48TPI disk drive had trouble reading the 48TPI diskette written on a
1.2MB 96TPI drive. The reason is not the media, it's the drive. Why?
It's because the medium is the same physical diskette. It cancels out of
the equation.
Using the wrong coercivity of diskette, you will NEVER
get a good,
reliable result. You MIGHT sometimes almost get away with using the
worng diskette. SOME idiots will claim that they "always use the wrong
diskette". WHY???
There are folks who enjoy claiming that their risky way of doing things is
better than paying the 10% extra for the correct product.
BTW, 720K and 1.4M are nominally 600 Oerstedt and 750
Oerstedt, which is
close enough that "getting away with" is a MUCH more likely proposition.
Let's try to keep the 3.5" diskettes out of the picture for now. The
720K
diskettes I meant were the 80-track 5.25" drives of the pre-PC/AT days.
These were quite popular in the late '70's-early '80's, and were
occasionally used with PC's, though they required a special driver be
loaded. I once made the hole in a few 720K diskettes because I needed the
media and felt I could get by. It worked, but it wasn't long before the
optical sensors in the early 3-1/2" drives gave way to the mechanical
feelers, and the holes had to be square. That wasn't very convenient, and,
by the way,
There are several problems with using the wrong drive. But some times
there isn't an adequate alternative.
Read/write currrent level:
With the exception of some of the preproduction Mitsubishi 4854 and
prototype Shugart 475s, all of the 1.2M drives have explicit provision for
TWO read/write current levels, explicitly for the purpose of permitting
reading, and even writing, 360K diskettes in the 1.2M drives. That is
typically NOT where the problem arises.
Motor speed:
8" is at 360RPM; 1.2M is at 360RPM 360K is at 300RPM
To do 360K in a 1.2M drive typically requires that the controller
Some of the controllers switched the data rate and in other cases the drive
switched speed.
compensate for the different motor speed by running
the 360K data transfer
rate at 300Kbps instead of the usual 250K bps. PC controllers can
normally handle that. Hooking a 1.2M drive to a non-PC controller that
expects an 8" drive will not provide for that, and therefore will not work
right for trying to do 360K diskettes.
Many current drives have dual spindle speeds (300, 360)
Weltec once made a 180RPM drive that would permit a PC 360K controller to
do 1.2M diskettes! (reliability was less than ideal)
THAT is typically not where the problem lies.
Track width:
Track width is a problem. Not only with 1.2m drives and 360K diskettes,
but also even with 720K/800K 5.25" drives (Shugart 465, Tandon TM100-4,
etc.) with 360K disk formats.
360K is about 1/2 mm per track, and the actual track itself is about 1/3mm
wide.
1.2M, 720K 5.25", etc. is about 1/4mm per track, and the actual track
itself is about 1/6mm wide.
When working with a virgin, bulk-erased 300 Oerstedt diskette, the 1.2m
(or 720K 5.25") drive CAN produce a diskette using every other track, that
is ALMOST acceptable. It will have tracks that are only 1/6mm wide, but
properly spaced at 1/2mm increments. You normally CAN get away with that,
unless/until:
if you EVER write to THAT diskette with a 360K drive, even "just erasing a
file", you will have replaced that 1/6mm wide sector with a 1/3mm wide
sector. From that point on, the diskette should NOT ever be written to
with the 1.2m drive, unless/until it has been bulk-erased and formatted
again.
A 96TPI drive can NOT do an acceptable job of REformatting or REwriting
over a 1/3mm wide track! Some people, using SOME drives have found that
it is ALMOST good enough, and can sometimes get away with it. But that's
like trying to use MY car at 100 mph. It just isn't built to do it RIGHT.
Therefore, it IS possible to do an emergency transfer diskette from 1.2M
to 360K, using a 300 Oerstedt diskette. But repeated back and forth
requires careful attention to detail to avoid ever trying to rewrite a
1/3mm wide track with the 1.2M drive.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
4:48 p.m.
New subject: Denver Area 6502-Group software
Wonder of wonders, I've found a printout of the manual and source code of
the old 6502-group FOCAL interpreter, written by "Wayne Wall and friends" at
the Colorado School of Mines.
It will be a while before I'm prepared to scan the things, but if someone's
in a hurry, I can send the printout if THEY will scan the things, the OCR
them and reconstruct the manual as a real manual and the assembler listing
as a text file with proper formatting. I'm pretty quick with the editor and
not so ambitious with tedious jobs like scanning . . .
Dick
27 Mar
27 Mar
4:02 a.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
On Sun, 26 Mar 2000, Richard Erlacher wrote:
I'm in agreement, pretty much with what's been
said here. Please see
embedded comments below.
Yes, but, given that the goal is to write a 48TPI 360K diskette, the
coercivity will be the same, since the media are the same. It's worth
Are you saying that a 300 Oerstedt diskette is the SAME as a 600 Oerstedt
diskette?? Is TRI-X camera film the same as Pan-X, also?
target medium is the 300-Oerstedt 48TPI 5.25"
diskette. The issue was that
the old 48TPI disk drive had trouble reading the 48TPI diskette written on a
1.2MB 96TPI drive. The reason is not the media, it's the drive. Why?
It's because the medium is the same physical diskette. It cancels out of
the equation.
The symptoms described (inability to read a diskette written in a 1.2M
drive, supposedly as a 360K) match TWO possibilities:
1) failure to bulk-erase and format in the 1.2M, when the diskette had
residual 1/3mm wide tracks.
2) use of a 600 Oerstedt diskette when trying to create a 360K.
Either (OR BOTH!) of those mistakes would give the symptoms described.
I fail to see how the media could be "cancels out of the equation". The
magnetic coercivity of the diskette would not magically be altered into
the correct one by any action of the drive. Setting the ASA dial on the
camera to 400 does NOT convert Pan-X film into TRI-X.
There are folks who enjoy claiming that their risky
way of doing things is
better than paying the 10% extra for the correct product.
Agreed
Let's try to keep the 3.5" diskettes out of
the picture for now. The 720K
Mentioned simply because:
the gap in coercivity of the different 5.25" diskettes is SIGNIFICANT.
The gap in coercivity of the different 3.5" diskettes is much less.
Therefore any success in using wrong diskettes in 3.5" should not be
extrapolated to apply to 5.25"
Some of the controllers switched the data rate and in
other cases the drive
switched speed.
Because it is on topic for collectors: The original IBM AT switched data
transfer rate. Many later went for dual spindle speed. Both methods
seemed to work OK. The Weltec 250Kbps/180RPM 1.2M was trying to stretch
things a little too far.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
5:43 a.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
On Mon, Mar 27, 2000 at 10:02:16AM -0800, Fred Cisin (XenoSoft) wrote:
On Sun, 26 Mar 2000, Richard Erlacher wrote:
I really think you guys are just miscommunicating. I too was surprised at
Dick's comment that you can use 360 KB and 1.2 MB disks interchangeably,
since I know it's not true. But I really don't think he meant it, especially
since his posts since then have concentrated on track width problems rather
than the bit rate within the track.
John Wilson
D Bit
I'm in agreement, pretty much with what's
been said here. Please see
embedded comments below.
Yes, but, given that the goal is to write a 48TPI 360K diskette, the
coercivity will be the same, since the media are the same. It's worth
Are you saying that a 300 Oerstedt diskette is the SAME as a 600 Oerstedt
diskette?? Is TRI-X camera film the same as Pan-X, also?
28 Mar
28 Mar
11:53 p.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
Gawd! Did I really say that? It's not what I meant!
plz see comments below.
Dick
----- Original Message -----
From: John Wilson <wilson(a)dbit.dbit.com>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, March 27, 2000 12:43 PM
Subject: Re: 360K in a 1.2M drive (was: Parallel port hard drives?
NO! What I mean is that the
problem as stated was to write a 48TPI diskette
intended for consumption by a C-64 in a drive intended for use with a 96TPI
HD diskette. There's a lot of folklore about what works, and what's
supposed to work, and how. Much of this is not only confusing, but also
incorrect.
On Mon, Mar 27, 2000 at 10:02:16AM -0800, Fred Cisin
(XenoSoft) wrote:
> On Sun, 26 Mar 2000, Richard Erlacher wrote:
> > I'm in agreement, pretty much with what's been said here. Please see
> > embedded comments below.
> > Yes, but, given that the goal is to write a
48TPI 360K diskette, the
> > coercivity will be the same, since the media are the same. It's worth
>
> Are you saying that a 300 Oerstedt diskette is the SAME as a 600
Oerstedt
diskette??
Is TRI-X camera film the same as Pan-X, also?
I really think you guys are just miscommunicating. I too was surprised at
Dick's comment that you can use 360 KB and 1.2 MB disks interchangeably,
since I know it's not true. But I really don't think he meant it,
especially
since his posts since then have concentrated on track
width problems
rather
than the bit rate within the track.
John Wilson
D Bit
11:48 p.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
I think we're homing in on the target topic now . . .
Please see embedded comments below.
Dick
----- Original Message -----
From: Fred Cisin (XenoSoft) <cisin(a)xenosoft.com>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, March 27, 2000 11:02 AM
Subject: Re: 360K in a 1.2M drive (was: Parallel port hard drives?
It cancels out because one wishes to write 48TPI on 48TPI-specified- media
but do so in a 96TPI HD drive.
720K
On Sun, 26 Mar 2000, Richard Erlacher wrote:
No, I'm not. I'm saying that the original problem, (assuming that i ever
grapsped it in the first place) was to write a 48TPI diskette. That means
that the 96TPI diskettes are not part of either the problem or the solution.
What's under study is the effect of writing a 48TPI diskette in a drive
intended for 96TPI use. Since there are no 600 or 720 Oerstedt diskettes
that are part of this problem, they need not be considered.
Nevertheless, it's probably helpful to understand WHY the different drives
and the media that go in them are important, in fact, definitive, to the
discussion.
I'm in agreement, pretty much with what's
been said here. Please see
embedded comments below.
Yes, but, given that the goal is to write a 48TPI 360K diskette, the
coercivity will be the same, since the media are the same. It's worth
Are you saying that a 300 Oerstedt diskette is the SAME as a 600 Oerstedt
diskette?? Is TRI-X camera film the same as Pan-X, also?
> target medium is the 300-Oerstedt 48TPI 5.25" diskette. The issue was
that
> the old 48TPI disk drive had trouble reading the
48TPI diskette written
on a
> 1.2MB 96TPI drive. The reason is not the media,
it's the drive. Why?
> It's because the medium is the same physical diskette. It cancels out
of
the equation.
The symptoms described (inability to read a diskette written in a 1.2M
drive, supposedly as a 360K) match TWO possibilities:
1) failure to bulk-erase and format in the 1.2M, when the diskette had
residual 1/3mm wide tracks.
2) use of a 600 Oerstedt diskette when trying to create a 360K.
Either (OR BOTH!) of those mistakes would give the symptoms described.
I fail to see how the media could be "cancels out of the equation". The
magnetic coercivity of the diskette would not magically be altered into
the correct one by any action of the drive. Setting the ASA dial on the
camera to 400 does NOT convert Pan-X film into TRI-X.
> There are folks who enjoy claiming that their risky way of doing things
is
better than
paying the 10% extra for the correct product.
Agreed
> Let's try to keep the 3.5" diskettes out of the picture for now. The
Mentioned simply because:
the gap in coercivity of the different 5.25" diskettes is SIGNIFICANT.
The gap in coercivity of the different 3.5" diskettes is much less.
Therefore any success in using wrong diskettes in 3.5" should not be
extrapolated to apply to 5.25"
I just wanted to keep them out of the discussion, since there are "720K"
diskettes in the 5-1/4" IBM-world with which they could be confused. I
don't believe that they actually format to a 720K capacity in applications
outside the "IBM"-PC world. They would, I guess, if one formatted them with
9 sectors of 512 bytes per track.
> Some of the controllers switched the data rate and in other cases the
drive
switched
speed.
Because it is on topic for collectors: The original IBM AT switched data
transfer rate. Many later went for dual spindle speed. Both methods
seemed to work OK. The Weltec 250Kbps/180RPM 1.2M was trying to stretch
things a little too far.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
29 Mar
29 Mar
6:56 a.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
Rumor has it that Richard Erlacher may have mentioned these words:
I just wanted to keep them out of the discussion, since
there are "720K"
diskettes in the 5-1/4" IBM-world with which they could be confused. I
don't believe that they actually format to a 720K capacity in applications
outside the "IBM"-PC world. They would, I guess, if one formatted them with
9 sectors of 512 bytes per track.
Or how about 18 sectors of 256 bytes per track.... like on my CoCos (1 360K
5.25 & 2 720K 3.5" drives made for a *lot* of storage 10 years ago... :-)
Roger "Merch" Merchberger
--
Roger "Merch" Merchberger --- sysadmin, Iceberg Computers
Recycling is good, right??? Ok, so I'll recycle an old .sig.
If at first you don't succeed, nuclear warhead
disarmament should *not* be your first career choice.
27 Mar
27 Mar
5:38 a.m.
New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
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New subject: 360K in a 1.2M drive (was: Parallel port hard drives?
Please see embedded comments below.
Dick
----- Original Message -----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, March 27, 2000 12:38 PM
Subject: Re: 360K in a 1.2M drive (was: Parallel port hard drives?
Are you trying to say that the coercivity of the disk (which is a
physical property of said disk) will somehow magically change when you
try to write a 360K format to it? If not, what are you saying?
> considering that toward the "maturity" of the 5.25" technology, the
media
That was my point. The way this thread got to this topic was that someone
was trying to write a 360 KB diskette witha 1.2MB drive and expected an old
Commodore (?) to read it. While it's quite possible, I doubt one would
call it likely.
is
the
There are TWO problems.
The disk matters.
The drive matters.
360K is 300 Oerstedt. 1.2M is 600 Oerstedt.
Yes, but, given that the goal is to write a 48TPI 360K diskette, the
coercivity will be the same, since the media are the same. It's worth > available throughtout the market were really
pretty much the same, and
the
Right up until the end, reputable disk manuafacturers put different media
into 360K and 1.2M disks. Period.
> drives were pretty similar too, except for the differences essential to
> maintaining their functionality. After the "new" had worn off the
1.2MB
These 'differences' included things like the coercivity of the disks and
the head width in the drives.
> Each step of the way created confusion in the market. Eventually the
> technology was abaondoned for the superior 3.5" drives. Nevertheless,
the
Actually, there's a nasty design defect in 3.5" disks. The side of the
shutter nearest the spindle is not clamped together in any way, and can
spring apart. This produces a disk that will slip into a drive OK but
which won't come out again (think of a standard locking barb). To get it
out involves dismantling the drive. I've had to sort this little mess out
a few times...
> media need not be considered for purposes of THIS discussion because the
> target medium is the 300-Oerstedt 48TPI 5.25" diskette. The issue was
that
> the old 48TPI disk drive had trouble reading the
48TPI diskette written
on a
> 1.2MB 96TPI drive. The reason is not the media,
it's the drive. Why?
> It's because the medium is the same physical diskette. It cancels out
of
the equation.
Oh, OK. If you're using a genuine 360K disk, then there is, indeed, no
problem with the disk (because it's the right one to use). But somebody
was claiming you could format a '1.2M' disk in a 1.2Mdrive with a 360K
format and then expect it to be reliably read by a 360K drive. That, in
my experience, doesn't work. Most of the time it won't even format
properly (the 1.2Mbyte drive being set to use a lower write current as I
mentioned a couple of messages back).
>
> > Using the wrong coercivity of diskette, you will NEVER get a good,
> > reliable result. You MIGHT sometimes almost get away with using the
> > worng diskette. SOME idiots will claim that they "always use the
wrong
> > diskette". WHY???
>
> There are folks who enjoy claiming that their risky way of doing things
is
better than
paying the 10% extra for the correct product.
Agreed! These people are fools. Period.
My data is worth a lot more than the cost of _any_ floppy disk you care
to name. It is _always_ worth using the best disks available (which means
also using the _correct_ disk ).
>
> > BTW, 720K and 1.4M are nominally 600 Oerstedt and 750 Oerstedt, which > > close enough that "getting away
with" is a MUCH more likely
proposition.
> >
> Let's try to keep the 3.5" diskettes out of the picture for now. The
720K
diskettes I
meant were the 80-track 5.25" drives of the pre-PC/AT days.
These were quite popular in the late '70's-early '80's, and were
occasionally used with PC's, though they required a special driver be
Actually, it was the same software (be it part of the bios or a separate
driver) that was used with 720K 3.5" disks.
> loaded. I once made the hole in a few 720K diskettes because I needed
^^^^^^^^^^^^^^
Presumably you're now talking about 3.5" disks.
Yes. I was disappointed with the results, however.
> media and felt I could get by. It worked, but it wasn't long before the
> optical sensors in the early 3-1/2" drives gave way to the mechanical
> feelers, and the holes had to be square. That wasn't very convenient,
and,
by the way,
Every 3.5" drive I have ever worked on uses mechanical sensors for write
protect, high density detect, and disk inserted. I have never seen
optical sensors, not even on the old Sony units [1]. In any case the
mechanical sensor is nearly always a thin 'pin' that goes through the
middle of the hole. It certainly doesn't check that it's a square hole.
[1] These being the full-height 600rpm units.... These drives did use
optical sensors -- slotted optoswitches on the spindle motor PCB. But
they were operated by spring-loaded plastic pieces that carried 'pins'
that went through the holes in the disk. So the actual interface between
the disk and the sensors was still a mechanical pin.
-tony
8815
days inactive
8818
days old
16 comments
8 participants
participants (8)
-
ard＠p850ug1.demon.co.uk -
cisin＠xenosoft.com -
edick＠idcomm.com -
marvin＠rain.org -
netsurfer_x1＠hotmail.com -
sipke＠wxs.nl -
wilson＠dbit.dbit.com -
zmerch＠30below.com