18 Jun
2007
18 Jun
'07
9:36 p.m.
Date: Mon, 18 Jun 2007 13:50:43 -0400
From: Sridhar Ayengar <ploopster at gmail.com>
Subject: Re: Pictures of My Machine Room (So Far)
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Message-ID: <4676C5F3.40609 at gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Roy J. Tellason wrote:
My first iteration of Windows 95 was on 3.5 inch floppy diskettes. At
some point, I wanted to make a backup copy on diskettes but couldn't
because the file sizes of the Windows distribution floppies was
1.8-1.9MB each. At the time I thought it was some sort of copy
protection. I assume they must have been able to format the discs for a
higher capacity - close to 2MB.
Does anyone know how?
On Sunday 17 June 2007 17:26, Fred Cisin wrote:
which were
Oh, well. I guess that it is like selling disks
based on their
unformatted capacity - a 2.8M ED disk is called "2.88" by IBM, and
was called "4 meg" by NeXT.
I have some boxes that had "1.44s" in them branded IBM and labeled "2.0MB"...
Indeed. All of the IBM 2.88's I have are labeled 4.0MB.
Peace... Sridhar
18 Jun
18 Jun
9:54 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
Wayne Smith wrote:
I would assume it's something similar to XDF. Probably not XDF itself
though, as that is an IBM thing.
You could have made a backup copy on diskettes by using the DOS DISKCOPY
command. It would have made a raw copy including the unusual format.
Peace... Sridhar
Date: Mon, 18
Jun 2007 13:50:43 -0400
From: Sridhar Ayengar <ploopster at gmail.com>
Subject: Re: Pictures of My Machine Room (So Far)
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Message-ID: <4676C5F3.40609 at gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Roy J. Tellason wrote:
My first iteration of Windows 95 was on 3.5 inch floppy diskettes. At
some point, I wanted to make a backup copy on diskettes but couldn't
because the file sizes of the Windows distribution floppies was
1.8-1.9MB each. At the time I thought it was some sort of copy
protection. I assume they must have been able to format the discs for a
higher capacity - close to 2MB.
Does anyone know how? On Sunday 17 June 2007 17:26, Fred Cisin wrote:
which were
Oh, well. I guess that it is like selling disks
based on their
unformatted capacity - a 2.8M ED disk is called "2.88" by IBM, and
was called "4 meg" by NeXT.
I have some boxes that had "1.44s"
in them branded IBM and labeled "2.0MB"...
Indeed. All
of the IBM 2.88's I have are labeled 4.0MB.
Peace... Sridhar
19 Jun
19 Jun
3:52 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
My first
iteration of Windows 95 was on 3.5 inch
floppy diskettes. At
some point, I wanted to make a backup copy on
diskettes but couldn't
because the file sizes of the Windows
distribution
floppies was
1.8-1.9MB each. At the time I thought it was
some
sort of copy
protection. I assume they must have been able to
format the discs for a
higher capacity - close to 2MB.
Does anyone know how?
I would assume it's something similar to XDF.
Probably not XDF itself
though, as that is an IBM thing. 
9:23 p.m.
On Tue, 19 Jun 2007, Mr Ian Primus wrote:
It's called DMF. 1.66 mb if I remember correctly.
There are other ways to increase the capacity of
floppies though - and with Linux it's quite possible
to get 1.75 mb reliably on one. (83 tracks, 21
sectors).
I would categorize as "something that you can get away with", rather than
"reliably" to use more tracks that the drive was designed for.
Will ALL of your drives step that many additional tracks?
--
Grumpy Ol' Fred cisin at xenosoft.com
9:40 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
Fred Cisin wrote:
I would categorize as "something that you can get
away with", rather than
"reliably" to use more tracks that the drive was designed for.
Will ALL of your drives step that many additional
tracks?
Chuckle ... Thinking about hard drives walking rather floppies.
Yes my drive has been known to step more than it was designed for.
--
Grumpy Ol' Fred cisin at xenosoft.com
9:50 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On 19 Jun 2007 at 21:23, Fred Cisin wrote:
I would categorize as "something that you can get
away with", rather than
"reliably" to use more tracks that the drive was designed for.
Will ALL of your drives step that many additional tracks?
Many diskette manufacturers put QA info on cylinder 80, side 0,
including manufacturing date, which can be very handy sometimes.
But I've got at least two drives in my collection that will "hang up"
on cylinder 82--the head sticks and will not retract--requiring
manual intervention. There are other drives where the position hits
a stop after cylinder 81.
And the manufacturer doesn't QA the media that far anyway.
I suspect that Superdrives and USB floppies won't go out that far,
though I haven't tested them.
Cheers,
Chuck
20 Jun
20 Jun
4 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
Many diskette manufacturers put QA info on cylinder
80, side 0,
including manufacturing date, which can be very
handy sometimes.
Neat - I didn't know that. I'll have to check for
that.
But I've got at least two drives in my collection
that will "hang up"
on cylinder 82--the head sticks and will not
retract--requiring
manual intervention. There are other drives where
the position hits
a stop after cylinder 81.
Interesting - I've never seen a drive do that. I
haven't had a problem with 82 cylinder disks, but I
can definitely see how some drives might not like it.
It's hardly in the spec. But then again, an 82
cylinder disk only requires it to step out to cylinder
81. I have had problems formatting 83 cylinder disks,
where the drive would be required to make it to
cylinder 82. Some drives do it fine, others don't.
Never had one get stuck though.
And the manufacturer doesn't QA the media that
far
anyway.
From what I've seen, they don't QA media at all
after
about 2001
-Ian
5:32 a.m.
New subject: Floppy Disc Capacities
At 11:50 PM 6/19/2007, Chuck Guzis wrote:
Many diskette manufacturers put QA info on cylinder 80,
side 0,
including manufacturing date, which can be very handy sometimes.
[...]
And the manufacturer doesn't QA the media that far anyway.
I know you're the guy who should know, but I didn't think that
diskette manufacturers did anything software-wise to the media
in most historical cases. Pre-formatted media would be another
matter, of course, and you'd think they'd QA that step to
reject media that wouldn't format.
- John
10:18 a.m.
New subject: Floppy Disc Capacities
On 20 Jun 2007 at 7:32, John Foust wrote:
I know you're the guy who should know, but I
didn't think that
diskette manufacturers did anything software-wise to the media
in most historical cases. Pre-formatted media would be another
matter, of course, and you'd think they'd QA that step to
reject media that wouldn't format.
Yes, it's on the preformatted media--and by no means all of it.
Still, it can be useful.
Cheers,
Chuck
19 Jun
19 Jun
12:24 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
Sridhar Ayengar wrote:
I would assume it's something similar to XDF.
Probably not XDF itself
though, as that is an IBM thing.
DMF, actually: http://en.wikipedia.org/wiki/Distribution_Media_Format
XDF, IMO, is unnecessarily complicated and not very robust -- they pack
8K clusters on the inner tracks like sardines. But it does indeed store
1.86MB on a DSHD 3.5" disk.
If I were to implement some additional-storage format, I'd probably put
more/larger sectors on the outer tracks where there is more surface
area. I believe Mac and Amiga formats did this, although I'm not aware
of the particulars.
You could have made a backup copy on diskettes by
using the DOS DISKCOPY
command. It would have made a raw copy including the unusual format.
No, it wouldn't. DOS DISKCOPY doesn't handle a single thing that is
outside the norm. CopyIIPC, Teledisk, Copywrite, ImageDisk, etc. can,
but hardly DOS DISKCOPY.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
2:16 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On 19 Jun 2007 at 14:24, Jim Leonard wrote:
> If I were to implement some additional-storage
format, I'd
probably put
more/larger sectors on the outer tracks where there is
more surface
area. I believe Mac and Amiga formats did this, although I'm not aware
of the particulars.
Yes, but the thing about XDF was that it used stock PC hardware. Mac
and Amiga used hardware that was very different--and varied the
rotational rate or the data clock rate to achieve their "zoned"
recording format.
XDF fits about all one can fit using the NEC 765 hardware. Consider
that the unformatted capacity of a track is 12500 bytes. So using an
8K+2K+1K+512 = 11776 bytes, which means that 94% of the track is used
for data storage. Contrast this with the normal 18*512 scheme; 9216
bytes of data for a data density of 73%. Even DMF with its 21*512
layout only gets 86% efficiency.
You needed special programs and drivers to read XDF, but it was as
close to using all of the available storage on a diskette with PC
hardware as was possible.
Cheers,
Chuck
3:47 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On 6/19/07, Chuck Guzis <cclist at sydex.com> wrote:
On 19 Jun 2007 at 14:24, Jim Leonard wrote:
The Mac did this, but the Amiga did not. The Mac single-sided 400K
drive did vary the drive speed - you could hear the zones. Later Macs
varied the clock rate through the IWM (Integrated Woz Machine), part
of the disk circuit.
Amigas had the same number of sectors per track throughout the entire
disk - 11 sectors of 512 bytes. They did, however, use non-standard
hardware rather than an off-the-shelf diskette controller like early
PCs. The digital control lines (step, motor on, etc.) came from one
of the 6821/6522/6526-like PIO chips (8520s to be specific), and the
raw MFM data was shuffled through a 4096-bit shift register in the
sound chip (Paula). The final component was the MFM<->binary
converter that was done as a series of logical mini-terms by the
graphics chip (Agnes). The effect of all of this was that an entire
track was slurped or dumped at once, allowing a very small
inter-sector gap compared to designs that read and wrote random
sectors on a track, leaving room for those two extra sectors compared
to the ordinary PC format.
Commodore did vary the bit clock to create 4 zones of sectors on 5.25"
floppies (2040/3040/4040/2031/1541/1571 for the PET, VIC-20, and
C-64).
-ethan
If I were to implement some additional-storage
format, I'd
probably put
more/larger sectors on the outer tracks where there is more surface
area. I believe Mac and Amiga formats did this, although I'm not aware
of the particulars.
Mac and Amiga used hardware that was very different--and varied the
rotational rate or the data clock rate to achieve their "zoned"
recording format.
4:16 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On 19 Jun 2007 at 18:47, Ethan Dicks wrote:
Commodore did vary the bit clock to create 4 zones of
sectors on 5.25"
floppies (2040/3040/4040/2031/1541/1571 for the PET, VIC-20, and
C-64).
Yup, you're correct. I was thinking of the C128/C64 GCR "zoned"
drives. But let's consdier the Amiga format and compare it to XDF.
The 250Kb/sec capacity for a DS2D diskette is 6250 bytes. So, 11*512
= 5632 bytes, giving a track utilization of about 90%. So XDF at 94%
still beats the Amiga with all of its fancy hardware--and XDF uses
standard gaps and address headers--and even puts an IAM on the track.
The Amiga could have done the same thing with nothing more than a
plain old 28-pin WD1770.
Cheers,
Chuck
4:11 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room
And thusly were the wise words spake by Jim Leonard
If I were to implement some additional-storage format, I'd probably put
more/larger sectors on the outer tracks where there is more surface
area. I believe Mac and Amiga formats did this, although I'm not aware
of the particulars.
Commodore's GCR format for its 8-bit computers also does this with
the most sectors on the first 17 tracks, then two less for the next
seven tracks then one less for next six tracks and again one less
for the last five tracks.
Cheers,
Bryan
20 Jun
20 Jun
4:45 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On 6/20/07, Jim Leonard <trixter at oldskool.org> wrote:
XDF, IMO, is unnecessarily complicated and not very robust -- they pack
8K clusters on the inner tracks like sardines. But it does indeed store
1.86MB on a DSHD 3.5" disk.
If I were to implement some additional-storage format, I'd probably put
more/larger sectors on the outer tracks where there is more surface
area. I believe Mac and Amiga formats did this, although I'm not aware
of the particulars.
With PC hardware, the sector size is irrelevant with respect to inner versus
outer tracks. 3.5 inch drives have a constant RPM and a constant write clock
rate, so will record the same number of bits on every track. That's where
the unformatted size of a diskette comes from, it's derived from the number
of bytes that will fit in one track without any gaps, headers or address
marks. If you could fiddle the write clock to use the 1 MHz rate for the
outer tracks you might get somewhere. You could work out the bits per lineal
inch at the inner and outer radii, and see if the media will support a
doubled clock rate at the outer tracks.
Regards,
Don Hills
8:01 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
Don Hills wrote:
I didn't explain myself well. I used to format high-quality diskettes
in the early 1990s as 21-sector instead of 18, and I consistently saw
errors after about a year of storage on the inner tracks (and never on
the outer tracks). I wasn't speaking from a storage standpoint, but
rather from a reliability standpoint.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
If I were to
implement some additional-storage format, I'd probably put
more/larger sectors on the outer tracks where there is more surface
area. I believe Mac and Amiga formats did this, although I'm not aware
of the particulars.
With PC hardware, the sector size is irrelevant with respect to inner
versus
outer tracks. 3.5 inch drives have a constant RPM and a constant write
clock
9:09 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On 20 Jun 2007 at 22:01, Jim Leonard wrote:
I didn't explain myself well. I used to format
high-quality diskettes
in the early 1990s as 21-sector instead of 18, and I consistently saw
errors after about a year of storage on the inner tracks (and never on
the outer tracks). I wasn't speaking from a storage standpoint, but
rather from a reliability standpoint.
You'd have likely seen nearly the same errors if you'd formatted the
floppies as 18 sectors. The issues of reliability come in when
writing, not reading. 21 sectors gives you something like an 8-byte
gap (i'll calculate it if you want). 8 bytes is .00064 of a track,
so if your spindle speed is too fast, you can easily overwrite the
gap.
But as far as bit-packing density goes, 18 and 21 sectors are the
same.
I would submit that by the early 1990's, there weren't any high-
quality DSHD diskettes. DSED were even worse.
Cheers,
Chuck
21 Jun
21 Jun
1:39 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On Wed, 2007-06-20 at 21:09 -0700, Chuck Guzis wrote:
I would submit that by the early 1990's, there
weren't any high-
quality DSHD diskettes. DSED were even worse.
I have:
8" disks that came with my PDP-11/73, some of which have labels dated in
the late 1970s and early 1980s. They all read fine in my RX02.
5.25" disks that came with my Sanyo MBC-<something> CP/M-86 machine.
They read fine.
3.5" DD disks formatted to around 400k single-sided for my Ensoniq
Mirage sampler, the oldest from around 1985, the newest being NOS 3.5"
DD disks off eBay. They all work fine, except for one or two that were
rewritten in a Mirage with a dodgy drive - I suspect they've got stuff
written "between tracks" and won't format correctly now.
3.5" DD disks from around 1990 for my Ensoniq EPS sampler. They work
fine.
3.5" HD disks from around 1995 for my E-Mu ESi-4000 sampler. They work
fine.
3.5" HD disks bought about four years ago - opened a packet recently and
half of them won't even format. One managed to fatally gunge the head
of my PC's floppy drive.
Gordon
9:03 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On 21 Jun 2007 at 9:39, Gordon JC Pearce wrote:
3.5" HD disks from around 1995 for my E-Mu
ESi-4000 sampler. They work
fine.
Have you reformatted any these lately? I find that diskettes written
back in 1995 are readable, but very few of them are reusable.
OTOH, the DS2D media we purchased in bulk right up through 2000 works
fine to this day. In the grand scheme of reliability, I think that
3.5" DSHD and DSED are not the best choices.
Cheers,
Chuck
9:49 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
Chuck Guzis wrote:
I would submit that by the early 1990's, there
weren't any high-
quality DSHD diskettes. DSED were even worse.
I can agree to that, sure.
I still have "fond" memories of the 3.5" "punchers" that would
"turn a
3.5" DSDD into DSHD". They worked just fine -- as long as you didn't
want to read the data 6 months later...
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
18 Jun
18 Jun
10:08 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On 18 Jun 2007 at 21:36, Wayne Smith wrote:
My first iteration of Windows 95 was on 3.5 inch
floppy diskettes. At
some point, I wanted to make a backup copy on diskettes but couldn't
because the file sizes of the Windows distribution floppies was
1.8-1.9MB each. At the time I thought it was some sort of copy
protection. I assume they must have been able to format the discs for a
higher capacity - close to 2MB.
Does anyone know how?
Uh-yup. Microsoft used a format they called DMF, for about 1.68MB--
21 sectors per track, with a very small gap between sectors. IBM had
a rather more complicated format called XDF, which used one 8K, one
2K, one 1K and one 512 byte sector on a track for about 1.84MB.
Handling the DMF format wasn't too hard, although if your drive was
marginal, it could create problems. The XDF actually used larger gap
sizes, but required special drivers. There was also an XDF format
for 5.25 HD that was about 1.6MB and one for 3.5 DSED which was about
3.84MB.
If you want to pack an amazing amount of data on a 3.5" DSHD, I
believe that there's a program for the Catweasel that will give you
something close to 4MB using a few tricks.
Cheers,
Chuck
19 Jun
19 Jun
1:39 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On Mon, 2007-06-18 at 22:08 -0700, Chuck Guzis wrote:
On 18 Jun 2007 at 21:36, Wayne Smith wrote:
I think I've mentioned before the peculiar disk format that Ensoniq used
on their 8-bit machines (Mirage and SQ-80 spring to mind) with five
1024-byte sectors and one 512-byte sector. On the Mirage the sample
and sequence data lives (mostly) in the 1024-byte sector, and the patch
and disk metadata (catalogue etc) live in the 512-byte sectors. The OS
is written to the first couple of full tracks, then some of the 512-byte
sectors further up the disk. No, I've no idea why. The Mirage sampler
is single-sided, the SQ-80 synth is double-sided. No idea why they did
that, either. My Mirage has a double-sided drive, like every other one
I've seen (even really early ones).
When they went to 16 bits, they went with a less bonkers 10 sectors per
track, 80 tracks, double-sided disk, but still their own special
filesystem.
Gordon
My first iteration of Windows 95 was on 3.5 inch
floppy diskettes. At
some point, I wanted to make a backup copy on diskettes but couldn't
because the file sizes of the Windows distribution floppies was
1.8-1.9MB each. At the time I thought it was some sort of copy
protection. I assume they must have been able to format the discs for a
higher capacity - close to 2MB.
Does anyone know how?
Uh-yup. Microsoft used a format they called DMF, for about 1.68MB--
21 sectors per track, with a very small gap between sectors. IBM had
a rather more complicated format called XDF, which used one 8K, one
2K, one 1K and one 512 byte sector on a track for about 1.84MB. 
6:46 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room ( So Far )]
On Tuesday 19 June 2007 01:08, Chuck Guzis wrote:
On 18 Jun 2007 at 21:36, Wayne Smith wrote:
The files section of the BBS I used to run, under the section for disk
utilities, included a fair pile of stuff that would let you play with all
sorts of different floppy formats, most of which would let you stuff more
than the "normal" amount of info on them...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
My first iteration of Windows 95 was on 3.5 inch
floppy diskettes. At
some point, I wanted to make a backup copy on diskettes but couldn't
because the file sizes of the Windows distribution floppies was
1.8-1.9MB each. At the time I thought it was some sort of copy
protection. I assume they must have been able to format the discs for a
higher capacity - close to 2MB.
Does anyone know how?
Uh-yup. Microsoft used a format they called DMF, for about 1.68MB--
21 sectors per track, with a very small gap between sectors. IBM had
a rather more complicated format called XDF, which used one 8K, one
2K, one 1K and one 512 byte sector on a track for about 1.84MB.
Handling the DMF format wasn't too hard, although if your drive was
marginal, it could create problems. The XDF actually used larger gap
sizes, but required special drivers. There was also an XDF format
for 5.25 HD that was about 1.6MB and one for 3.5 DSED which was about
3.84MB.
If you want to pack an amazing amount of data on a 3.5" DSHD, I
believe that there's a program for the Catweasel that will give you
something close to 4MB using a few tricks. 
18 Jun
18 Jun
11:26 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
My first iteration of Windows 95 was on 3.5 inch
floppy diskettes. At
some point, I wanted to make a backup copy on diskettes but couldn't
because the file sizes of the Windows distribution floppies was
1.8-1.9MB each. At the time I thought it was some sort of copy
protection. I assume they must have been able to format the discs for a
higher capacity - close to 2MB.
Does anyone know how?
FDRead/FDFormat did that in the glorious DOS days...
19 Jun
19 Jun
4:55 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
On Tue, Jun 19, 2007 at 03:26:06AM -0300, Alexandre Souza wrote:
FDRead/FDFormat did that in the glorious DOS
days...
Ahh, bad memories. Hey, I thought, lets use fdformat to make bigger
floppies so I have to waste less time swapping disks when I make a
backup!
Oops.
I vaguely recall that as well as cramming more sectors in per track,
fdformat and the like would write a couple of extra tracks as well.
--
David Cantrell | London Perl Mongers Deputy Chief Heretic
"Cynical" is a word used by the naive to describe the experienced.
George Hills, in uknot
6:30 p.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (SoFar)]
Hi,
I vaguely recall that as well as cramming more sectors
in per
track, fdformat and the like would write a couple of extra tracks
as well.
Never tried adding extra sectors, but using a couple of extra tracks was a
very common trick in the early Atari ST days.
TTFN - Pete.
4:20 a.m.
New subject: Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]
My first iteration of Windows 95 was on 3.5 inch
floppy diskettes. At
some point, I wanted to make a backup copy on diskettes but couldn't
because the file sizes of the Windows distribution floppies was
1.8-1.9MB each. At the time I thought it was some sort of copy
protection. I assume they must have been able to format the discs for a
higher capacity - close to 2MB.
Does anyone know how?
Thats Microsofts DMF (Distribution Media Format) - smaller gaps, more
sectors (21/track iirc) - ImageDisk can copy them.
Smaller gaps mean less room to realign when writing sectors into an
existing track. DMF disks are OK for "Distribution Media" because they
are written one (presumably in a continuous track) and do not have to
be re-written on countless slightly varying drives...
Generally you can get more space on a disk by going with a larger sector
size (as long as size * #sectors works out to near the end of a track),
as this reduces the number of gaps you need. I recall a DOS TSR called
"2M" which got nearly 2 Megs of data on a disk by using big (2k iirc)
sectors.
Regards,
Dave
--
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.classiccmp.org/dunfield/index.html
6394
days inactive
6396
days old
26 comments
17 participants
participants (17)
-
alexandre-listas＠e-secure.com.br -
bfranchuk＠jetnet.ab.ca -
bpope＠wordstock.com -
cclist＠sydex.com -
cisin＠xenosoft.com -
classiccmp＠memory-alpha.org.uk -
dave06a＠dunfield.com -
david＠cantrell.org.uk -
dmhills＠gmail.com -
ethan.dicks＠gmail.com -
gordon＠gjcp.net -
ian_primus＠yahoo.com -
jfoust＠threedee.com -
ploopster＠gmail.com -
rtellason＠verizon.net -
trixter＠oldskool.org -
wayne.smith＠charter.net