6 Sep
2007
6 Sep
'07
2:44 p.m.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140155187682
How to make an unreliable medium even LESS reliable.
6 Sep
6 Sep
3:09 p.m.
--- Al Kossow <aek at bitsavers.org> wrote:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140155187682
How to make an unreliable medium even LESS reliable.
Hehe - I remember seeing those advertised in computer
magazines way back when. I used to do the same thing
sometimes, only I used a drill. Either that, or a
paper cutter could cut the entire corner off the disk.
Funny thing was, disks modified in this fashion never
gave me any problems. I know that the media is
different, and that it should have been unreliable,
but, back then anyway, it worked just fine. I even
remember reading an old disk as recently as last year,
and it still worked.
I never had the problem with floppies ten years ago
that I have now with brand new disks. I think that at
some point, the quality of the media just went through
the floor.
-Ian
3:25 p.m.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140155187682
> How to make an unreliable medium even LESS reliable.
On Thu, 6 Sep 2007, Mr Ian Primus wrote:
Funny thing was, disks modified in this fashion never
gave me any problems. I know that the media is
different, and that it should have been unreliable,
but, back then anyway, it worked just fine. I even
remember reading an old disk as recently as last year,
and it still worked.
The difference in coercivity of 720K v 1.4M is slight - 600 v ~730,
as opposed to 300 v 600 for 360K v 1.2M. Therefore, you can usually get
away with the reduction in reliability, where you couldn't with 5.25".
I never had the problem with floppies ten years ago
that I have now with brand new disks. I think that at
some point, the quality of the media just went through
the floor.
Arg, don't get me started on how they don't make things like they usta.
--
Grumpy Ol' Fred cisin at xenosoft.com
3:35 p.m.
--- Mr Ian Primus <ian_primus at yahoo.com> wrote:
Aw Al I used to nibble-notch my Commie 64 disks all
the bloomin time LOL. I know, apples and oranges. The
disks were double sided in fact, but you had to notch
'em before you flipped them over.
--- Al Kossow <aek at bitsavers.org> wrote:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140155187682
How to make an unreliable medium even LESS
reliable. Funny thing was, disks modified in this fashion
never
gave me any problems. I know that the media is
different, and that it should have been unreliable,
but, back then anyway, it worked just fine. I even
remember reading an old disk as recently as last
year,
and it still worked.
Many quality branded disks could "double up" on the
density. I couldn't believe it when a friend told me
that for quads he was using regular DD floppies. Yeah
back then floppies were big business I guess, and in
order to avoid a bad name, they were over engineered.
I never had the problem with floppies ten years ago
that I have now with brand new disks. I think that
at
some point, the quality of the media just went
through
the floor.
It probably has a lot to do w/the media, but I also
think the new drives are basically crap also.
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4:30 p.m.
On 6 Sep 2007 at 12:35, Chris M wrote:
Many quality branded disks could "double
up" on the
density. I couldn't believe it when a friend told me
that for quads he was using regular DD floppies. Yeah
back then floppies were big business I guess, and in
order to avoid a bad name, they were over engineered.
Let's be clear here--I interpret 5.25 DD to be 360K (250K data rate
at 300 RPM) at 48 tpi. And "quad" to me is the same data rate but
narrower tracks for 96 tpi and 720K. AFAIK, the only difference
between DSDD and DSQD was the supposed certification provided by the
mnaufacturer. I never found any difference at all.
Cheers,
Chuck
4:34 p.m.
--- Chuck Guzis <cclist at sydex.com> wrote:
Let's be clear here--I interpret 5.25 DD to be
360K
(250K data rate
at 300 RPM) at 48 tpi. And "quad" to me is the same
data rate but
narrower tracks for 96 tpi and 720K. AFAIK, the
only difference
between DSDD and DSQD was the supposed certification
provided by the
mnaufacturer. I never found any difference at all.
Well I wish you could have been clear about this ~20
years back. I thus wouldn't have blown all those extra
cordobas on senseless certification! Sheesh!
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7 Sep
7 Sep
6:18 p.m.
Let's be clear here--I interpret 5.25 DD to be
360K (250K data rate
at 300 RPM) at 48 tpi. And "quad" to me is the same data rate but
narrower tracks for 96 tpi and 720K. AFAIK, the only difference
between DSDD and DSQD was the supposed certification provided by the
mnaufacturer. I never found any difference at all.
When the PC was the only current machine with 5.25" drives, I bought
several boxes of name=brand 5.25" DD disks that would format reliably as
40 cylinder disks on a PC and similarly on other machines (and which are
still readable), but which would not format reliably as 80 cylinder disks.
And yes, I am clueful enough not be be complaining they didn't work as HD
disks on a PC/AT. What I a talking about is formatting them as 80
cylinder disks on BBC micros, TRS80s, etc.
I assume it was something like an increased background noise level. I cna
think of no other explanation.
Incidentally, I was given a couple of plastic carrier bags full of
bulk-erased DEC RX50 disks. Although these were only ever indended to be
used as signle-sided disks, I have never had one fail to format 80
cylinders _double_ sided.
-tony
8:35 p.m.
On 7 Sep 2007 at 23:18, Tony Duell wrote:
And yes, I am clueful enough not be be complaining
they didn't work as HD
disks on a PC/AT. What I a talking about is formatting them as 80
cylinder disks on BBC micros, TRS80s, etc.
I assume it was something like an increased background noise level. I cna
think of no other explanation.
Dunno, but when we were selling our own-branded Dysan 100 tpi
diskettes, I was told by the Dysan sales tech that the formulation
was exactly the same as the 48 tpi versions; that only the
verification process was different. Maybe the UK got all of the
floor sweepings; I don't know.
I do know that the certifiers used for DSDD diskettes were programmed
to toss a cookie that verified fine on one side but not the other
into the "about to become SSDD" media pile.
That's not to say that the occasional branded-and-certified-as-100-
tpi diskette failed to format either. There was a reason that
everyone had a flawing mechanism of some sort built into most
operating systems. And our application was a bit tougher than most
as we were packing something like 950K in a 77cyl * 2sides *12sect *
512bytes format using GCR and an elevated clock rate. This was a
couple of years before Osborne was putting, what, 90K on a 5.25"
floppy?
Cheers,
Chuck
6 Sep
6 Sep
3:44 p.m.
On 6 Sep 2007 at 12:09, Mr Ian Primus wrote:
I never had the problem with floppies ten years ago
that I have now with brand new disks. I think that at
some point, the quality of the media just went through
the floor.
Indeed, when the price of a box of 1.44 DSHD (Fuji, IIRC) was around
$50 and 720K DS2D diskettes were a fraction of that, it paid to punch
the holes. I had a hole punch at one time, but then just decided to
stack up a pile of them in the drill press and drill the hole out
with a brad-point bit. Worked just fine--and I still have some of
those "modified" diskettes that are still very readable. Not at all
like the "new" DSHD media that I have.
You could also do the same trick, albeit with less success to get
DSED from DS2D. But then DSED was never that reliable anyway...
What surprises me is the occasional 5.25" diskette that shows up for
conversion that's written on DSHD media but formatted for 360K 2D.
Many still are quite readable after 20 years.
Cheers,
Chuck
6:15 p.m.
On 6 Sep 2007 at 11:44, Al Kossow wrote:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140155187682
How to make an unreliable medium even LESS reliable.
Well, I don't know. In the universe of "read-and-write unreliable
media", floppies rate as pretty darned reliable from the standpoint
of "How many years can elapse between writing and reading before the
medium becomes unreadable?"
Hard disks seem to develop problems regularly (bumpers turning to goo
etc., not being able to locate the correct controller to read the old
stuff), tapes seem to have all sorts of problems from QIC cartridges
shedding to the wonderful experience of oxide sticking to the next
layer on 1/2" 9-track tape (it really makes a mess on a 200 ips
streamer). MO carts that fail mysteriously or problems locating the
appropriate drive. I don't know how USB flash will fare in 30 years.
Punched cards are still pretty good. I can still read the first
floppies I wrote over 30 years ago just fine--and have 3.5" diskettes
more than 20 years old that read just fine.
Basalt tablets--now there's a reliable medium.
Cheers,
Chuck
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9 comments
6 participants
participants (6)
-
aek＠bitsavers.org -
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
chrism3667＠yahoo.com -
cisin＠xenosoft.com -
ian_primus＠yahoo.com