24 Oct
2015
24 Oct
'15
6:59 p.m.
I know Chuck Guzis has written about this, but I don't see that he's done
so publicly in the last few years, so I thought I'd ask here about his and
others' views on the perennial question of whether (some) 3.5" DSHD disks
can be reliably used in DSDD-only drives. The oft-repeated claim is that
writing can appear to work just fine, but that even a few months later read
errors will occur.
On <http://www.retrotechnology.com/herbs_stuff/guzis.html> Chuck was quoted
as (actually, correct me if I'm wrong -- it's a little hard to be sure this
was Chuck's words) as saying "Usually, they're just fine, with the error
rate approximately the same, whether or not 2D or HD media was used." Just
before that, he said "I think that the overall quality of DSHD 3.5" media
isn't what it used to be, so that might contribute to the general
impression that 3.5" HD diskettes used as 2D aren't reliable. I have
problems enough finding reliable 3.5" DSHD floppies used as such." Chuck et
al., what's your feeling now, both on the overall reliability of HD disks
in DD drives, and on whether it depends on how recently the disks were
produced?
Elsewhere on the page (I don't recall now if it was Herb or Chuck that said
it) it was conjectured that HD disks that have never been formatted as HD,
-OR- disks that have gone through a good degaussing, will have better luck
retaining data. What does everyone think about this? And would an
electromagnetic library security system (the kind that's like a tube
through which checked-out materials are put; often with a caution not to
put tapes or floppies through it) be a suitable degausser?
--
Eric Christopherson
24 Oct
24 Oct
7:14 p.m.
On Sat, 24 Oct 2015, Eric Christopherson wrote:
I know Chuck Guzis has written about this, but I
don't see that he's done
so publicly in the last few years, so I thought I'd ask here about his and
others' views on the perennial question of whether (some) 3.5" DSHD disks
can be reliably used in DSDD-only drives. The oft-repeated claim is that
writing can appear to work just fine, but that even a few months later read
errors will occur.
That was certainly the case with 5.25", but THAT was a difference between
300 Oersted and 600 Oersted. WAY OFF.
But, with 3.5" disks, the difference is between 600 Oersted and 720?
Oersted. THAT is close enough.
For BEST results, I think that it would be better to use the right ones,
but unlike 5.25" disks, with 3.5", you can get away with it.
Elsewhere on the page (I don't recall now if it
was Herb or Chuck that said
it) it was conjectured that HD disks that have never been formatted as HD,
-OR- disks that have gone through a good degaussing, will have better luck
retaining data. What does everyone think about this? And would an
electromagnetic library security system (the kind that's like a tube
through which checked-out materials are put; often with a caution not to
put tapes or floppies through it) be a suitable degausser?
Probably a very good idea.
Some Windoze machines will check for existing format before formatting,
and be somewhat uncooperative about reformatting as a different density.
The one time that it is critically important to bulk-erase or use virgin
disks is when writing 48tpi disks in a 96tpi drive. When a 96tpi drive
RE-writes a 48tpi disk, as 48tpi, it can not clear the edges of the track
completely.
Are we really running short of "720K" floppies?
I thought that AOHell had sent out enough snail spam with disks to supply
us forever!
9:06 p.m.
On Sat, Oct 24, 2015 at 9:14 PM, Fred Cisin <cisin at xenosoft.com> wrote:
On Sat, 24 Oct 2015, Eric Christopherson wrote:
OK. I just wanted to ask, in case running a floppy through that contraption
would actually mess up its magnetization so badly that it couldn't then be
used.
I know Chuck Guzis has written about this, but I
don't see that he's done
so publicly in the last few years, so I thought I'd ask here about his and
others' views on the perennial question of whether (some) 3.5" DSHD disks
can be reliably used in DSDD-only drives. The oft-repeated claim is that
writing can appear to work just fine, but that even a few months later
read
errors will occur.
That was certainly the case with 5.25", but THAT was a difference between
300 Oersted and 600 Oersted. WAY OFF.
But, with 3.5" disks, the difference is between 600 Oersted and 720?
Oersted. THAT is close enough.
For BEST results, I think that it would be better to use the right ones,
but unlike 5.25" disks, with 3.5", you can get away with it.
Elsewhere on the page (I don't recall now if it was Herb or Chuck that said
it) it was conjectured that HD disks that have
never been formatted as HD,
-OR- disks that have gone through a good degaussing, will have better luck
retaining data. What does everyone think about this? And would an
electromagnetic library security system (the kind that's like a tube
through which checked-out materials are put; often with a caution not to
put tapes or floppies through it) be a suitable degausser?
Probably a very good idea.
Some Windoze machines will check for existing format before formatting,
and be somewhat uncooperative about reformatting as a different density.
The one time that it is critically important to bulk-erase or use virgin
disks is when writing 48tpi disks in a 96tpi drive. When a 96tpi drive
RE-writes a 48tpi disk, as 48tpi, it can not clear the edges of the track
completely.
Are we really running short of "720K" floppies?
I thought that AOHell had sent out enough snail spam with disks to supply
us forever!
I had to laugh at that. Another list member recently told me that AOL disks
are the ones he's had the most success with recently. I don't know how many
of them were 720KB, though. In any case, I think I only started getting AOL
dis(c|k)s in the CD-ROM era, unfortunately.
But anyway, it does look like DD disks are more expensive; that, coupled
with the fact that a lot of HD disks in the wild are going to be newer,
makes me want to buy some HD ones instead. But that second part might be
more of a bad thing, if it's true that floppy QA went downhill later on.
On Sat, Oct 24, 2015 at 10:48 PM, Chuck Guzis <cclist at sydex.com> wrote:
My opinions on Herb's retrotechnology site still
hold--with one addition.
Thanks for that.
You can sometimes get 3.5" HD disks that have been used, but now refuse to
accept a format by first performing a DC erase. That is, get a very strong
rare-earth magnet, and moving in a helical path (i.e. circular, starting
close to the disc, slowing moving away), perform an erase pass. Following
with an AC erase can sometime inject new life into the disk. I've tried
this several times and it does seem to work.
Fascinating -- I didn't know there were AC and DC magnetic fields. How
strong is "very strong", and would the library device I mentioned count
toward "an AC erase"? Should I assume that just doing an AC erase would be
insufficient?
--
Eric Christopherson
10:01 p.m.
On 10/24/2015 09:06 PM, Eric Christopherson wrote:
Fascinating -- I didn't know there were AC and DC
magnetic fields.
How strong is "very strong", and would the library device I mentioned
count toward "an AC erase"? Should I assume that just doing an AC
erase would be insufficient?
The AC unit I use is a VHS tape bulk eraser. It's pretty strong and has
a limited working time--maybe 2-3 minutes before the thermal cutout
interrupts. Let it cool for a few minutes and get back to work.
How strong a DC erase? I suppose that one of these magnets could well
lift a 100 lbs. Scary strong.
--Chuck
25 Oct
25 Oct
3:39 a.m.
This list seems to me to be populated with "build your own" types, so make your
own degausser.
Decades ago I repaired the tape eraser at the TV station I worked at. Once I saw how it
was built I built my own. Take a transformer (something about 100 watt or more) pull the
laminations out (the hard part) line up all the 'E's put them back. Discard the
'I's.
It will buzz like mad and get hot in a minute but produce a very strong AC magnetic field.
Keep it away from your shadow mask color TV!
Joe
On Oct 25, 2015, at 1:01 AM, Chuck Guzis <cclist at
sydex.com> wrote:
On 10/24/2015 09:06 PM, Eric Christopherson wrote:
Fascinating -- I didn't know there were AC
and DC magnetic fields.
How strong is "very strong", and would the library device I mentioned
count toward "an AC erase"? Should I assume that just doing an AC
erase would be insufficient?
The AC unit I use is a VHS tape bulk eraser. It's pretty strong and has a limited
working time--maybe 2-3 minutes before the thermal cutout interrupts. Let it cool for a
few minutes and get back to work.
How strong a DC erase? I suppose that one of these magnets could well lift a 100 lbs.
Scary strong.
--Chuck
1:05 p.m.
On Sun, Oct 25, 2015, Joseph Lang wrote:
This list seems to me to be populated with "build
your own" types, so make your own degausser.
Decades ago I repaired the tape eraser at the TV station I worked at. Once I saw how it
was built I built my own. Take a transformer (something about 100 watt or more) pull the
laminations out (the hard part) line up all the 'E's put them back. Discard the
'I's.
It will buzz like mad and get hot in a minute but produce a very strong AC magnetic
field.
Keep it away from your shadow mask color TV!
Joe
> On Oct 25, 2015, at 1:01 AM, Chuck Guzis <cclist at sydex.com> wrote:
>
> On 10/24/2015 09:06 PM, Eric Christopherson wrote:
>
>
>> Fascinating -- I didn't know there were AC and DC magnetic fields.
>> How strong is "very strong", and would the library device I mentioned
>> count toward "an AC erase"? Should I assume that just doing an AC
>> erase would be insufficient?
I guess my last question (would doing just an AC erase, by whatever
means, always be insufficient) got lost.
>
> The AC unit I use is a VHS tape bulk eraser. It's pretty strong and has a
limited working time--maybe 2-3 minutes before the thermal cutout interrupts. Let it cool
for a few minutes and get back to work.
>
> How strong a DC erase? I suppose that one of these magnets could well lift a 100
lbs. Scary strong.
>
> --Chuck
>
--
Eric Christopherson
9:19 p.m.
On Sun, Oct 25, 2015 at 3:05 PM, Eric Christopherson <
echristopherson at gmail.com> wrote:
On Sun, Oct 25, 2015, Joseph Lang wrote:
Also, do I always need to cover one hole on a 3.5" HD disk when using it in
an HD-capable drive? Or does the disk or the OS notice it's been formatted
as DD and then treat it accordingly?
--
Eric Christopherson
This list seems to me to be populated with
"build your own" types, so
make your own degausser.
Decades ago I repaired the tape eraser at the TV
station I worked at.
Once I saw how it was built I built my own. Take a transformer
(something
about 100 watt or more) pull the laminations out (the hard part) line up
all the 'E's put them back. Discard the 'I's.
It will buzz like mad and get hot in a minute but
produce a very strong
AC magnetic field.
Keep it away from your shadow mask color TV!
Joe
> On Oct 25, 2015, at 1:01 AM, Chuck Guzis <cclist at sydex.com> wrote:
>
> On 10/24/2015 09:06 PM, Eric Christopherson wrote:
>
>
>> Fascinating -- I didn't know there were AC and DC magnetic fields.
>> How strong is "very strong", and would the library device I mentioned
>> count toward "an AC erase"? Should I assume that just doing an AC
>> erase would be insufficient?
I guess my last question (would doing just an AC erase, by whatever
means, always be insufficient) got lost.
>
> The AC unit I use is a VHS tape bulk eraser. It's pretty strong and
has
a limited working time--maybe 2-3 minutes before the thermal cutout
interrupts. Let it cool for a few minutes and get back to work.
>
> How strong a DC erase? I suppose that one of these magnets could well
lift a
100 lbs. Scary strong.
>
> --Chuck
>
--
Eric Christopherson
9:44 p.m.
On 10/25/2015 09:19 PM, Eric Christopherson wrote:
Also, do I always need to cover one hole on a
3.5" HD disk when using
it in an HD-capable drive? Or does the disk or the OS notice it's
been formatted as DD and then treat it accordingly?
In *most* applications, the extra hole in the HD floppy changes the
operating parameters of the drive itself. (There are exceptions, notably
on some IBM systems of the PS/2 variety).
Of course, on a DD-only drive, the drive is blind to the extra hole.
One of the things you have to keep on eye peeled for when handling a
bunch of 3.5" floppies--to read the disk on an HD drive, you need to
cover the hole.
--Chuck
11:12 p.m.
[HD 3.5" disks and the density-select hole]
Of course, on a DD-only drive, the drive is blind to
the extra hole.
Not always! The original Sony full-height drives (the 600rm ones) have a
disk-inserted sensor positioned exactly where that hole is. So if you insert
an HD disk the drive doesn't detect it. It is rumoured this was deliberate
(positioning of the HD hole) so that you couldn't use the wrong disks and
have reliability problems.
-tony
26 Oct
26 Oct
12:52 a.m.
On 10/25/2015 11:12 PM, tony duell wrote:
Not always! The original Sony full-height drives (the
600rm ones)
have a disk-inserted sensor positioned exactly where that hole is. So
if you insert an HD disk the drive doesn't detect it. It is rumoured
this was deliberate (positioning of the HD hole) so that you couldn't
use the wrong disks and have reliability problems.
Yes, the Sony OA-D32 drives. Single-sided 600 RPM. One *could* argue,
that, given the data rate, it's already "high density" (of a sort). I
worked out a BIOS for a Z80 CP/M system called a Preis around 1982, when
the drive was pretty new. It was a luggable and had a hard disk option
as well. I don't know whatever became of them--but I still have the
BIOS listing in my files.
I don't think that anyone had any thoughts about putting such a drive in
with a controller that would do 1Mbps. Sony never alluded to it in
their documentation.
The battle of the "pocket floppies", IIRC, hadn't yet been settled in
1982. We could just as well have wound up with the Shugart/Dysan 3.25"
floppy--or worse, the Hitachi 3" disks as used in the Amstrad machines.
I've still got a couple of 3.5" ED drives, along with blank media--there
was a trend that didn't last long...
--Chuck
12:46 p.m.
Yes, the Sony OA-D32 drives. Single-sided 600 RPM. One *could* argue,
that, given the data rate, it's already "high density" (of a sort). I
I would say it's normal double density (the spacing of the flux transitions
on the disk is the same as on a PC 720K disk) but a high data rate due
to the double spindle speed.
There's a double-head version too.
Not surprisingly I've worked on a lot of these drives, HP used them in many
of their HPIB disk units. There was a later half-height version (not a high density
drive, same format as the full height ones) which shares a lot of parts with the
Apple 800K drive.
-tony
6:26 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Steven
Hirsch
Sent: 25 October 2015 13:08
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)
On Sat, 24 Oct 2015, Fred Cisin wrote:
Someone had boxes of these they were willing to sell recently and there was
no take up.
I would say they are being trashed because no one has space and have moved
to floppy emulators.
Dave
Are we really running short of "720K"
floppies? I thought that AOHell
had sent out enough snail spam with disks to supply us forever!
Indeed, but the quality of those diskettes was dreadful.
-- 
11:44 a.m.
On 10/25/2015 7:07 AM, Steven Hirsch wrote:
On Sat, 24 Oct 2015, Fred Cisin wrote:
More the Service provided from the disk.?
Are we really running short of "720K"
floppies? I thought that AOHell
had sent out enough snail spam with disks to supply us forever!
Indeed, but the quality of those diskettes was dreadful.
12:03 p.m.
>> Are we really running short of
"720K" floppies? I thought that AOHell
>> had sent out enough snail spam with disks to supply us forever!
> Indeed, but the quality of those diskettes was dreadful.
On Sun, 25 Oct 2015, ben wrote:
More the Service provided from the disk.?
Blaming the medium for the content?
Or, . . .
if you were putting something like that onto disks,
would you spring the money for high quality ones?
12:31 p.m.
On 10/25/2015 1:03 PM, Fred Cisin wrote:
Blaming the medium for the content?
Or, . . .
if you were putting something like that onto disks,
would you spring the money for high quality ones?
I suspect the reason they failed was not service
but a) PC's had games b) Ma Bell wanted a arm and a leg
for long distance connections.
Ben.
12:40 p.m.
New subject: AOL (Was: Substituting DSHD for DSDD disks (or DS2D
[AOL]
On Sun, 25 Oct 2015, ben wrote:
I suspect the reason they failed was not service
but a) PC's had games b) Ma Bell wanted a arm and a leg
for long distance connections.
Some of their early efforts to COMPETE AGAINST the internet helped
establish outfits like Netcom, and were a boost to ISPs.
Perhaps Ed (still using AOL) would have some insight into what caused
their decline.
--
Grumpy Ol' Fred cisin at xenosoft.com
1:07 p.m.
On Sun, Oct 25, 2015, ben wrote:
On 10/25/2015 1:03 PM, Fred Cisin wrote:
Actually, in many areas of the US, they had local dialup numbers that
connected to their service through Tymnet and/or Telenet, so long
distance didn't apply. Maybe in rural areas those access points were
still long distance, though. But AOL itself had per-minute premium rates
for quite a while.
--
Eric Christopherson
Blaming the medium for the content?
Or, . . .
if you were putting something like that onto disks,
would you spring the money for high quality ones?
I suspect the reason they failed was not service
but a) PC's had games b) Ma Bell wanted a arm and a leg
for long distance connections.
Ben.
1:36 p.m.
On Sun, 25 Oct 2015, Eric Christopherson wrote:
Actually, in many areas of the US, they had local
dialup numbers that
connected to their service through Tymnet and/or Telenet, so long
distance didn't apply. Maybe in rural areas those access points were
still long distance, though. But AOL itself had per-minute premium rates
for quite a while.
3 years ago, when I stayed at my mother's house taking care of her, it
took me a month to find out that she did not have unlimited local calling!
Adding DSL on the phone account reduced the phone bill a lot.
That house is now mine. AT&T DSL here sucks.
2:03 p.m.
On 10/25/2015 01:36 PM, Fred Cisin wrote:
3 years ago, when I stayed at my mother's house
taking care of her,
it took me a month to find out that she did not have unlimited local
calling! Adding DSL on the phone account reduced the phone bill a
lot.
That house is now mine. AT&T DSL here sucks.
I'm finally (after years of 1.5M DSL service) going to get some decent
speeds--or so I'm told. When the Qwest wanted to expand service in my
neighborhood, they asked to purchase a bit of my land (I didn't even
know it was mine) for a "temple of boxes". I said okay, as long as DSL
would be offered. Qwest was a good as their word--this was in 2004.
Before that, it was POTS.
All of the sudden, late last spring, contractor trucks showed up and
started stringing fiber and 200 pair copper on the poles here (current
service is buried, not on poles). They've spent much of the summer,
stringing cable and punching wires at the terminal. I've been told that
I'll be receiving 20Mbps service and a new modem by the 11th of next
month. My monthly fees won't change.
So why is CenturyLink doing this? Is it a matter of improving service?
From the techs working at the temple, it turns out that it's nothing
like that. It seems that all that buried cable is slowly migrating down
the hillside to the extent that it's going to need replacement. That's
miles of copper--and probably not cheap (I got to see what an 1800 pair
cable looks like).
So fiber feeds the temple and the 200 pair copper is for folks down the
road (about 2.5 miles).
So maybe, if the weather be good, I'll be getting some worthwhile DSL
service before Thanksgiving. That would be nice.
--Chuck
1:37 p.m.
On 10/25/2015 01:07 PM, Eric Christopherson wrote:
Actually, in many areas of the US, they had local
dialup numbers
that connected to their service through Tymnet and/or Telenet, so
long distance didn't apply. Maybe in rural areas those access points
were still long distance, though. But AOL itself had per-minute
premium rates for quite a while.
You speak as if dial-up access to the 'Net no longer exists:
http://help.netzero.net/nzhelp/support-home-page/service-help/internet-acce…
Maybe NZ has discontinued it, but I've always kept a list of the numbers
in case of emergency.
--Chuck
26 Oct
26 Oct
7:38 a.m.
On 10/24/2015 09:14 PM, Fred Cisin wrote:
Are we really running short of "720K"
floppies?
I went around all the local places that I could think of a couple of years
ago and bought up whatever stock of floppies that I could find (and picking
sure were slim). Quite a few boxes of 3.5" HD, a few boxes of 5.25" DD, but
zero 3.5" DD and 5.25" HD.
3.5" HD media just killed off the use of 3.5" DD and 5.25" HD, I suppose.
I'm not sure what the reason for my finding a few boxes of 5.25" DD was,
though - perhaps it was just produced in sufficient volume for there to
still be a few survivors kicking around.
I've never had any luck finding used disks anywhere locally; people are a
bit too concerned about data theft these days, and all of that seems to go
straight to landfill.
cheers
Jules
7:43 a.m.
On 2015-10-26 11:38 AM, Jules Richardson wrote:
On 10/24/2015 09:14 PM, Fred Cisin wrote:
Not long ago I bought a 100 from floppydisk.com for use with my vintage
HP's they where reputed to be used but looked like new to me. They seem
to work fine, I have not had any fail to format or fail in use.
Paul.
Are we really running short of "720K"
floppies?
I went around all the local places that I could think of a couple of
years ago and bought up whatever stock of floppies that I could find
(and picking sure were slim). Quite a few boxes of 3.5" HD, a few
boxes of 5.25" DD, but zero 3.5" DD and 5.25" HD.
3.5" HD media just killed off the use of 3.5" DD and 5.25" HD, I
suppose. I'm not sure what the reason for my finding a few boxes of
5.25" DD was, though - perhaps it was just produced in sufficient
volume for there to still be a few survivors kicking around.
I've never had any luck finding used disks anywhere locally; people
are a bit too concerned about data theft these days, and all of that
seems to go straight to landfill.
cheers
Jules
27 Oct
27 Oct
6:53 a.m.
Paul Berger wrote:
On 2015-10-26
11:38 AM, Jules Richardson wrote:
On
10/24/2015 09:14 PM, Fred Cisin wrote:
Are we really running short of "720K"
floppies?
I went around all the local places that I could think of a couple of
years ago and bought up whatever stock of floppies that I could find
(and picking sure were slim). Quite a few boxes of 3.5" HD, a few
boxes of 5.25" DD, but zero 3.5" DD and 5.25" HD. 3.5" HD
media just killed off the use of 3.5" DD and 5.25" HD, I
suppose. I'm not sure what the reason for my finding a few boxes of
5.25" DD was, though - perhaps it was just produced in sufficient
volume for there to still be a few survivors kicking around.
I've never
had any luck finding used disks anywhere locally; people
are a bit too concerned about data theft these days, and all of that
seems to go straight to landfill.
Not long ago I bought a 100 from floppydisk.com for use with my
vintage HP's they where reputed to be used but looked like new to me.
They seem to work fine, I have not had any fail to format or fail in use.
6:47 a.m.
On 2015-10-27 10:53 AM, Jerome H. Fine wrote:
With
regard to 5 1/4" DD media, a couple of decades ago, I rescued a
few hundred
RX50 type media from a DEC system which I have not had a chance to
look at.
Eventually, they will hopefully be copied at which point they could be
made available
for the postage to send them. Note that I am in Toronto (M2R 3G3).
So please
send a note if this media is still needed and I will be sure to hold
onto the floppies.
NOTE that all are obviously USED.
I also have a
few dozen 5 1/4" HD floppies which are also DEC RX33 media
along with a few dozen 3.5" HD media which are also DEC RX23 media.
These RX23 media still be available in reasonable quantities since
they were
probably the last of the floppy media which was widely used when a
3.5" HD
floppy drive was still a popular item. NOTE that all are obviously USED.
I am not interested for myself, but which type of floppy media were they?
I probably have about 500 hundred 8" floppy media some of which
are already LLF (Low Level Formatted) to the IBM standard of
SSSD or 488 blocks. A few have even been LLF with DSDD
(Double-Sided, Double-Density) even though they have only the
Single-Sided Index hole since I have a switch on my DSD 880/30
which supports using an 8" floppy that has the Single-Sided index
hole as an 8" Double-Sided floppy. In DEC naming convention,
a SSSD 8" floppy is an RX01 LLF, a SSDD 8" floppy is an RX02
LLF and a DSDD 8" floppy is an RX03 LLF.
The DSD 880/30 has a single RX03 floppy drive. The DPDT switch
which I installed supports the use of an 8" floppy with the index hole
in the Single-Sided location to be used and detected by the RX03
drive as if the index hole was in the Double-Sided position - which
avoids the need to punch a second pair of holes.
For those individuals who are using RT-11, my DYX.SYS (RX02
device driver) supports the use of a bounce buffer which is required
when the user buffer is in Extended Memory above the 256 KB
boundary. I have mentioned this in the past, but it seems that no
one uses the DYX.SYS under RT-11 any more. In an emergency,
it is always possible to use DUP to copy the complete floppy media
to a small 512 KB file on a drive which supports 22-bit user addresses
which is usually available at least on the system drive for RT-11 to
be able to run a virtual job that requires low memory overlays.
Note that this DYX.SYS is not ready for general release since it still
does not make use of Extended Memory instead of a very large
buffer in Low Memory. But in an absolute emergency, it could still
me made available.
Jerome Fine The ones I got where the 3.5" DSDD as used in 9122 mod D and S and
several disk diskette combo machines and also the 9114 HPIL drive. I
would really like to get a HP 9895 8" drive but they seem to be few and
far between.
Paul.
Paul Berger
wrote:
On
2015-10-26 11:38 AM, Jules Richardson wrote:
On
10/24/2015 09:14 PM, Fred Cisin wrote:
Are we really running short of "720K"
floppies?
I went around all the local places that I could think of a couple of
years ago and bought up whatever stock of floppies that I could find
(and picking sure were slim). Quite a few boxes of 3.5" HD, a few
boxes of 5.25" DD, but zero 3.5" DD and 5.25" HD. 3.5"
HD media just killed off the use of 3.5" DD and 5.25" HD, I
suppose. I'm not sure what the reason for my finding a few boxes of
5.25" DD was, though - perhaps it was just produced in sufficient
volume for there to still be a few survivors kicking around.
I've
never had any luck finding used disks anywhere locally; people
are a bit too concerned about data theft these days, and all of that
seems to go straight to landfill.
Not long ago I bought a 100 from floppydisk.com for use with my
vintage HP's they where reputed to be used but looked like new to
me. They seem to work fine, I have not had any fail to format or
fail in use. 
26 Jan
26 Jan
2:48 p.m.
On Tue, Oct 27, 2015 at 7:47 AM, Paul Berger <phb.hfx at gmail.com> wrote:
I would really
like to get a HP 9895 8" drive but they seem to be few and far between.
Same here. And I'd like to get an 82901M 5.25" drive, and a 9122C HD 3.5".
I was surprised to learn that the 9895, while it supports standard IBM
3740 single-density format, uses an HP-proprietary M2FM double-density
format.
3:10 p.m.
On 2016-01-26 6:48 PM, Eric Smith wrote:
On Tue, Oct 27, 2015 at 7:47 AM, Paul Berger
<phb.hfx at gmail.com> wrote:
Well I managed to get a working controller card got a 9895 and I have it
connected to a pair of Shugart SA860 drives I have had forever so 8"
diskettes, my 9835A is very happy.
Paul.
I would really
like to get a HP 9895 8" drive but they seem to be few and far between.
Same
here. And I'd like to get an 82901M 5.25" drive, and a 9122C HD 3.5".
I was surprised to learn that the 9895, while it supports standard IBM
3740 single-density format, uses an HP-proprietary M2FM double-density
format.
4:59 p.m.
On 01/26/2016 02:48 PM, Eric Smith wrote:
I was surprised to learn that the 9895, while it
supports standard
IBM 3740 single-density format, uses an HP-proprietary M2FM
double-density format.
So did Intel on the MDS. I don't recall if there was any significant
difference between Intel and HP MMFM encoding, however.
--Chuck
5:27 p.m.
On Tue, Jan 26, 2016 at 5:59 PM, Chuck Guzis <cclist at sydex.com> wrote:
On 01/26/2016 02:48 PM, Eric Smith wrote:
Entirely different. As was DEC RX02.
I was surprised to learn that the 9895, while it
supports standard
IBM 3740 single-density format, uses an HP-proprietary M2FM
double-density format.
So did Intel on the MDS. I don't recall if there was any significant
difference between Intel and HP MMFM encoding, however.
9:07 p.m.
On Tue, Jan 26, 2016 at 7:04 PM, Chuck Guzis <cclist at sydex.com> wrote:
You've lost me there. Both HP and Intel were true
MMFM;
There's more to it than the basic channel code.
IBM 3740 and Ohio Scientific 8-inch both use "true FM" for the channel
code, but they aren't compatible.
The HP 9895 M2FM and Intel M2FM may be the same channel code, but the
address marks are different, etc.
27 Jan
27 Jan
8:49 a.m.
On 01/26/2016 09:07 PM, Eric Smith wrote:
On Tue, Jan 26, 2016 at 7:04 PM, Chuck Guzis
<cclist at sydex.com>
wrote:
That's exactly what I was asking. But you implied that the RX02 was
MMFM, which, in my experience is not the case.
MFM is a (1,3) RLL code; MMFM is a (1,4) code. AFAIK, RX02 is a
combination of (0,1) for headers and (1,3) for data. WHat the decoded
clock and data bits actually mean is a separate issue.
--Chuck
You've lost me there. Both HP and Intel were
true MMFM;
There's more to it than the basic channel code.
IBM 3740 and Ohio Scientific 8-inch both use "true FM" for the
channel code, but they aren't compatible.
The HP 9895 M2FM and Intel M2FM may be the same channel code, but
the address marks are different, etc.
2:07 p.m.
On Wed, Jan 27, 2016 at 9:49 AM, Chuck Guzis <cclist at sydex.com> wrote:
That's exactly what I was asking. But you implied
that the RX02 was MMFM,
which, in my experience is not the case.
The double-density RX02 data fields are in a modifed MFM, which is
what M2FM or MMFM stands for. It doesn't use the same encoding rules
as are most commonly used for M2FM, though.
DEC's M2FM uses the same encoding as MFM except for the case of a run
of exactly four consecutive one bits.
data: 011110
MFM encoded:
DCDCDCDCDCD
00101010100
DEC M2FM encoded:
DCDCDCDCDCD
01000100010
DEC claimed that this was done because using normal MFM encoding, the
data field could contain a pattern that matches a preample fllowed by
an ID mark. I am dubious of that claim; I did an exhaustive search and
was unable to find any sequence of data bits which, MFM-encoded, would
match any of the RX02 mark patterns (standard 3740 patterns for index,
ID, single-density data, and single-density deleted data, and
non-standard patterns for double-density data and double-density
deleted data).
3:06 p.m.
On 01/27/2016 02:07 PM, Eric Smith wrote:
The double-density RX02 data fields are in a modifed
MFM, which is
what M2FM or MMFM stands for. It doesn't use the same encoding
rules as are most commonly used for M2FM, though.
...and that was exactly my objection. This becomes a case of the Monty
Python "Basingstoke in Westphalia" and "our Cole Porter". The RX02
MFM
(and I believe I touched on the rationale) may be "modified MFM", but
it's not modified in the standard (1,4) RLL encoding that the rest of
the world uses/used. I can conceivably change a couple of encodings for
FM, but that doesn't make it MFM. For example, not allowing 4
consecutive clock and data 1 bits in a row (I could, for example, leave
out a clock bit.). Come to think of it, that's exactly what standard
IBM 3740 address marks do, but nobody calls that "MFM".
If you insist that the 3740 format *defines* FM, then you're leaving out
a lot of recording formats that use (0,1) RLL, but not 3740 conventions.
Honestly, you DEC guys need to get out more.
--Chuck
1:51 a.m.
On Tue, 26 Jan 2016, Chuck Guzis wrote:
So did Intel on the MDS. I don't recall if there
was any significant
difference between Intel and HP MMFM encoding, however.
The initial CRC value ($0000 vs. $FFFF) and the header (six vs. four
bytes) are different, but the encoding was quite identical. The Intel
header format was similar (or even the same) as the "standard"
soft-sectored formats (i.e. with head and sector length bytes). The HP
format knows only single-sided floppies with up to 32 sectors (0 to 31).
The address mark bytes are different, too.
Christian
26 Jan
26 Jan
9:10 p.m.
You make me feel lucky. I have all 3 (almost, I have the low density HP 9121 rather than
an HD 9122 so I can use it on my HP 85)... Haven't restored or even powered up the
recently acquired HP 9895 yet, but the HP 82901A and the HP 9121D now work great. Quite
low capacity (270k?) due to the weird LIF formatting, formats 35 tracks but uses only 33,
out of the 40. I wonder why. I don't know anything yet about the 8" HP 9895 and
its encoding. I thought they were surprisingly high capacity (1.2 MB?) considering their
age. Am I right?
Marc
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Eric Smith
Sent: Tuesday, January 26, 2016 2:48 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)
On Tue, Oct 27, 2015 at 7:47 AM, Paul Berger <phb.hfx at gmail.com> wrote:
I would really
like to get a HP 9895 8" drive but they seem to be few and far between.
Same here. And I'd like to get an 82901M 5.25" drive, and a 9122C HD 3.5".
I was surprised to learn that the 9895, while it supports standard IBM
3740 single-density format, uses an HP-proprietary M2FM double-density format.
9:20 p.m.
On Tue, 26 Jan 2016, CuriousMarc wrote:
You make me feel lucky. I have all 3 (almost, I have
the low density HP
9121 rather than an HD 9122 so I can use it on my HP 85)... Haven't
restored or even powered up the recently acquired HP 9895 yet, but the
HP 82901A and the HP 9121D now work great. Quite low capacity (270k?)
due to the weird LIF formatting, formats 35 tracks but uses only 33, out
of the 40. I wonder why.
Partially because the original 5.25" drives (Shugart SA400) were 35 track
(#0 - #34), not 40.
Single sided single density was about 100K. Double sided double density
could be up to 400K, with 360K being typical.
I don't know anything yet about the 8" HP
9895
and its encoding. I thought they were surprisingly high capacity (1.2
MB?) considering their age. Am I right?
8" double sided double denwsity is, indeed 1.2M or thereabouts, varying by
format choices.
5.25" "high" density mimics 8".
One company, NEC, made their 5.25" "high density" format the same as
their 8" format, and even ran their 3.5" drives at 360RPM, instead of the
more common 300RPM, so that they could have the same format on those,
also.
--
Grumpy Ol' Fred cisin at xenosoft.com
10:07 p.m.
82901A and the
HP 9121D now work great. Quite low capacity (270k?) due to
the weird LIF formatting, formats 35 tracks but uses only 33, out of the
40. I wonder why.
Partially because the original 5.25" drives (Shugart SA400)
were 35 track (#0
- #34), not 40.
30 Jan
30 Jan
6:28 p.m.
On Jan 26, 2016, at 10:07 PM, Fred Cisin <cisin at xenosoft.com> wrote:
I don't even remember, . . . Does LIF also reserve some space for substitution for
bad sectors?
(there were a higher percentage in those days) Yes, LIF had two spare tracks. That
explains it. 33 tracks + 2 spare tracks matches the 35 original Shugart drives you
mention. Mystery solved, thanks.
82901A and the HP 9121D now work great. Quite low
capacity (270k?) due to the weird LIF formatting, formats 35 tracks but uses only 33, out
of the 40. I wonder why.
Partially because the original 5.25" drives (Shugart
SA400) were 35 track (#0 - #34), not 40. 
26 Oct
26 Oct
8:58 a.m.
On Mon, 26 Oct 2015, Jules Richardson wrote:
On 10/24/2015 09:14 PM, Fred Cisin wrote:
I suspect Athana still stocks them.
g.
--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
http://www.diy-cockpits.org/coll - Go Collimated or Go Home.
Some people collect things for a hobby. Geeks collect hobbies.
ScarletDME - The red hot Data Management Environment
A Multi-Value database for the masses, not the classes.
http://scarlet.deltasoft.com - Get it _today_!
Are we really running short of "720K"
floppies?
I've never had any luck finding used disks anywhere locally; people are a bit
too concerned about data theft these days, and all of that seems to go
straight to landfill.
24 Oct
24 Oct
8:48 p.m.
On 10/24/2015 06:59 PM, Eric Christopherson wrote:
I know Chuck Guzis has written about this, but I
don't see that he's done
so publicly in the last few years, so I thought I'd ask here about his and
others' views on the perennial question of whether (some) 3.5" DSHD disks
can be reliably used in DSDD-only drives. The oft-repeated claim is that
writing can appear to work just fine, but that even a few months later read
errors will occur.
My opinions on Herb's retrotechnology site still hold--with one addition.
You can sometimes get 3.5" HD disks that have been used, but now refuse
to accept a format by first performing a DC erase. That is, get a very
strong rare-earth magnet, and moving in a helical path (i.e. circular,
starting close to the disc, slowing moving away), perform an erase pass.
Following with an AC erase can sometime inject new life into the disk.
I've tried this several times and it does seem to work.
As Fred mentioned, the "write them now, but not read them later" case
applies to HD 5.25" disks written in DD mode. But even that's not a
sure thing. I've handled batches of DD-written 3M HD floppies that were
more than 20 years old and they read fine.
I've never tried DD writing onto ED floppies. I suspect that it won't
work at all. The coating characteristics are just too different.
--Chuck
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ard＠p850ug1.demon.co.uk -
bfranchuk＠jetnet.ab.ca -
cc＠informatik.uni-stuttgart.de -
cclist＠sydex.com -
cisin＠xenosoft.com -
curiousmarc3＠gmail.com -
dave.g4ugm＠gmail.com -
echristopherson＠gmail.com -
geneb＠deltasoft.com -
jhfinedp3k＠compsys.to -
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