Mark Frischknecht

On 2011-10-31 15:23:27 +0000, Mark Frischknecht said:

> On 2011-10-30 22:05:28 +0000, Michael J. Mahon said:
>
>> Wholly Mindless <wholly@whollymindless.com> wrote:
>>> Can we at least make sure that we document that for *some* people 3.5" HD
>>> disks DO NOT ALWAYS work? That way when someone finds this at 3am after a
>>> Walgreens run and is frantically trying to format the box of 10 they bought
>>> and they start looking on the net, they don't assume their drive is bad and
>>> start tearing it apart?
>>>
>>> My experience has definitely been down in the 1 of 10 or maybe even less
>>> work. It is also possible that newer drives (or older drives for that
>>> matter) are more tolerant. We just haven't done definitive research - or at
>>> least most of us haven't.
>>
>> The difference in coercivity of HD vs. DD media is much less for 3.5"
>> diskettes than it is for 5.25" diskettes, so _some_ drives will be able to
>> write to them well enough, but HD media is outside the tolerance for DD
>> media, so no DD drive was designed to write it to saturation (or erase
>> previously written data, either). You can apparently find DD drives that
>> can write reliably, but that's depending on luck, not on proper design
>> margins.
>>
>> Proper design margins are the only thing that allows us to treat the analog
>> world as if it were digital.
>>
>> If the media is not written (magnetized) to saturation, then the domains
>> storing the data have a greater tendency to decay, resulting eventually in
>> unreadable data.
>>
>> Note that it's the writing that's the issue. Once a diskette is stably
>> written, any drive should be able to read it.
>>
>> In the case of 5.25" diskettes, the coercivity of HD media is so much
>> greater than DD that HD diskettes are universally unusable.
>> -michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
>
> You are inviting disaster by using 3.5 HD disks as DD disks.
> As I have told people before in other places:
>
> Never use 1.44 as a 800k....
> 1.44 meg disks need a stronger magnetic field to set the bits and
> formatting it as 800k the floppy heads use a weaker magnetic field
> which will cause corruption. And the bits on the disk will rapidly
> revert to the original random alignment.
>
> DSDD 3.5 has a Coercivity of 600 osterads
> DSHD 3.5 has a Coercivity of 720 osterads
>
> Higher coercivity means a stronger magnetic field is needed to set the
> bits, and a 800k drives or a 1.44 drives formatting in 800k mode do not
> have a strong enough magnetic field to properly set the bits.
>
> It may seem to work but in the end it will fail.
>
> V/R
>
> Mark Frischknecht

ps here is a intresting read on why not to use HD disks as DD disks
http://www.retrotechnology.com/herbs_stuff/guzis.html

Tony Cianfaglione

On Mon, 31 Oct 2011, Mark Frischknecht wrote:

> It may seem to work but in the end it will fail.

Gee, Mark... I've been using them repeatedly in my II's for over 25
years - when does the end come?

Mark Frischknecht

On 2011-10-31 21:10:21 +0000, Tony Cianfaglione said:

> On Mon, 31 Oct 2011, Mark Frischknecht wrote:
>
>> It may seem to work but in the end it will fail.
>
> Gee, Mark... I've been using them repeatedly in my II's for over 25
> years - when does the end come?

Probably when it is most inconvenient. I have seen the problem happen,
at Kfest a programmer was handing out copies of software h programed
on 3.5 HD disks formatted as 800k and none of the disks were readable.
So please keep your sarcastic comments to yourself.

V/R

Mark Frischknecht

David Schmidt

On 10/31/2011 6:46 PM, Mark Frischknecht wrote:
> On 2011-10-31 21:10:21 +0000, Tony Cianfaglione said:
>
>> On Mon, 31 Oct 2011, Mark Frischknecht wrote:
>>
>>> It may seem to work but in the end it will fail.
>>
>> Gee, Mark... I've been using them repeatedly in my II's for over 25
>> years - when does the end come?
>
> Probably when it is most inconvenient. I have seen the problem happen,
> at Kfest a programmer was handing out copies of software h programed on
> 3.5 HD disks formatted as 800k and none of the disks were readable.

That's the thing: as another poster pointed out, it seems to be
particular to the drive. Perhaps Tony's drive is one of those
highly-capable ones. I've not been lucky, myself. Generally, the disk
will fail immediately after writing - so I just don't do it.

Tony Cianfaglione

On Mon, 31 Oct 2011, Mark Frischknecht wrote:

> Probably when it is most inconvenient. I have seen the problem happen, at
> Kfest a programmer was handing out copies of software h programed on 3.5 HD
> disks formatted as 800k and none of the disks were readable. So please keep
> your sarcastic comments to yourself.

It's possible that my drives are running at a slightly higher power
level as I use custom made power supplies which push out a bit more juice.
Maybe this is resulting in better results for me in this regard. I'm not
being sarcastic; it's just that I've had very good results with HD disks
as DD disks for a quarter century.

Mark Frischknecht

On 2011-11-01 02:29:39 +0000, Tony Cianfaglione said:

> On Mon, 31 Oct 2011, Mark Frischknecht wrote:
>
>> Probably when it is most inconvenient. I have seen the problem happen,
>> at Kfest a programmer was handing out copies of software h programed
>> on 3.5 HD disks formatted as 800k and none of the disks were readable.
>> So please keep your sarcastic comments to yourself.
>
> It's possible that my drives are running at a slightly higher power
> level as I use custom made power supplies which push out a bit more
> juice. Maybe this is resulting in better results for me in this regard.
> I'm not being sarcastic; it's just that I've had very good results
> with HD disks as DD disks for a quarter century.

Np sorry about snapping at you I had just gotten home form a 7:00 pm tp
7:00 am shift at Intel..

Kevin Dady

On Oct 31, 8:29*pm, Tony Cianfaglione <ab...@chebucto.ns.ca> wrote:
> On Mon, 31 Oct 2011, Mark Frischknecht wrote:
> > Probably when it is most inconvenient. I have seen the problem happen, at
> > Kfest a programmer was handing out copies of software h programed *on3.5 HD
> > disks formatted as 800k and none of the disks were readable. So please keep
> > your sarcastic comments to yourself.
>
> * * It's possible that my drives are running at a slightly higher power
> level as I use custom made power supplies which push out a bit more juice..
> Maybe this is resulting in better results for me in this regard. *I'm not
> being sarcastic; it's just that I've had very good results with HD disks
> as DD disks for a quarter century.

not to nitpick but supplies dont push, they provide, ie you hook a 1
amp load to a 0.5amp supply, its going to provide 1 amp as that is
what the circuit consumes, which could cause your supply to simply
overheat and shut down, or if its big iron and coils, melt down and
burn up. Likewise if your circuit is only drawing 0.5 amp's you could
hook a 500 amp battery to the thing and its still only going to use
0.5 amps.