Did the Apple II use single-density 5.25" drives?

[slickr...@gmail.com]

I got my first computer, an Apple IIGS back in 1988. I don't recall ever seeing single sided or single density disks in the stores back then. I only ever used double sided, double density (DSDD) disks. Years later I added a SuperDrive and was able to use high density 3.5" disks in it.

I think I read somewhere that the Apple II's 5.25" drives could use single sided, single density disks just fine. Was that true and that the "double density" aspect was wasted?

I know for a fact that they were single sided, and the other side was wasted unless you had a hole-punch tool to remove the write protection on the other side. I also know that MS-DOS systems could use both sides simultaneously. Howver, what about the "single density" aspect?

I've never seen such a disk in either 3.5" or 5.25". I know for a fact that 5.25" high density disks will NOT work in the AppleDisk 5.25" drive, given that somebody traded me a blank HD disk at one point for a formatted ProDOS disk that I was unable to format or use (and he gave me several others from the pack.

So, were they single density or double density drives?
Did single-density disks even exist, or were they something extremely short lived and quickly replaced with double density the way the 400K disks were replaced with 800K disks on the Mac (400K 3.5" disks was something else I'd only seen as an option with the HFS FST or System 6.0.7 on the Mac).

==
to reply, remove the news from my address.

[David Schmidt]

On 6/6/2013 1:22 PM, slickr...@gmail.com wrote:
> I think I read somewhere that the Apple II's 5.25" drives could use single sided, single density disks just fine.

You read that Apple II drives can use single sided, double density disks
just fine. In terms of magnetic coatings, there really is only DD and HD.

> Was that true and that the "double density" aspect was wasted?

No, the "double sided" aspect was wasted unless you notch and flip.
There was only a read head on the bottom of the Disk II drive.

> I also know that MS-DOS systems could use both sides simultaneously. Howver, what about the "single density" aspect?

Correct, other drive mechanisms had heads on both the top and bottom, so
they could use both sides without flipping. "Single density" really
refers to the recording method (FM vs MFM). Google for more.

> So, were they single density or double density drives?

Well, the drives use popularly named "double density" media - though the
GCR encoding dictated by the Woz controller board didn't produce
capacities as dense as possible relative to the media capability. We're
really talking about two different things here... recording scheme vs.
track width. Track width is, in media terms, either DD or HD. (Other
much less popular variants exist that I'm ignoring now.)

> [...] 400K disks were replaced with 800K disks on the Mac

That particular difference was only single-sided vs. double-sided. Both
drives used the same DD media.

[Michael Black]

There wasn't "single density" until "double density" came along, at which
point they had to put a name on what had existed before.

It's the controller that sets the density. If you look at
early floppy disk ICs that do double density, there is a means of
switching it between single and double. The same drive could be used.
Later the ability to switch density generally went away. I remember
lookig at single IC controllers in a databook and noticing that, and there
was at least one operating system, FLEX for the 6809, that needed the
first sector to be single density for some reason, and the later
controllers were incompatible.

If I recall properly, High Density needed a different drive, something
like it ran t a faster speed.

So the average (non-Apple) drives started out with about 90K of storage
space, single density and single sided. That doubled when either double
density or double sided drives came along, I can't remember which came
first, and then doubled again when the other of the two arrived.

There was also the issue that originally 5.25" drives were 35tracks, and
when 40track drives appeared (and software to go with them, the software
had to know to move to the extra tracks), that increased capacity a bit.

There were various attempts at a smaller drive, including small floppy
disks with a hub like the well known 3.5". There were 3" disks, I think
with a hard shell, the poor people who bought into those early likely got
stuck, and then finally a standardization on the 3.5" with the hard shell
that we know and love.

Out of the box they had higher capacity 80 tracks per side, so that would
double the capacity, and no hardware needed.


I guess it was the 1.2meg 5.25" drives that had the faster rotation speed.
But then the high density drives appeared, they had narrower tracks, which
meant a need for narrower read/write heads, and a different makeup of the
coating on the 5.25" floppies, which is why the HD floppies are not seen
as reliable in double density drives.

I suddenly can't remember how 3.5" drives got to be High Density.

And none of this has much to do with Apple.

Michael

[David Schmidt]

On 6/6/2013 3:22 PM, Michael Black wrote:
> It's the controller that sets the density. If you look at early floppy
> disk ICs that do double density, there is a means of switching it
> between single and double.

This is FM vs. MFM that I talked about in my response. Single/double
density all about how "densely" bits are encoded by the controller, and
we're generally talking about standard Shugart controllers (nothing to
do with Apple). Double density vs. High density indicates track width
capability (48TPI vs. 96TPI).

> ability to switch density generally went away. I remember lookig at
> single IC controllers in a databook and noticing that, and there was at
> least one operating system, FLEX for the 6809, that needed the first
> sector to be single density for some reason, and the later controllers
> were incompatible.

The Epson QX-10 shares this capability/requirement. There are others as
well.

[iv...@ivanexpert.com]

Can it be fairly said that, apart from "certification", SD floppies and DD floppies are the same thing, and that the terms "single-density" and "double-density" don't apply to Apple II 5.25" disks, because they refer to whether a drive encoded a disk with FM or MFM, whereas an Apple II drive encodes disks with GCR, which, in terms of data density, is in between?

IBM PC floppy drives could store 180K per side with MFM (aka double-density), but that was using 40 tracks, so by my math, it's 157.5K if it were 35 tracks -- which is still more than the Apple II's 140K using 35 tracks with GCR. (Which is more than the 78.75K you'd get from 35 tracks with FM, aka single-density.)

Was GCR chosen because MFM encoding wasn't a viable or economical option at the time, and it was a higher-density method than FM? And why not 40 tracks (which would have yielded 160K per side with DOS 3.3) instead of 35? Same reason?

[David Schmidt]

On 6/6/2013 3:57 PM, iv...@ivanexpert.com wrote:
> Can it be fairly said that, apart from "certification", SD floppies and DD floppies are the same thing, and that the terms "single-density" and "double-density" don't apply to Apple II 5.25" disks, because they refer to whether a drive encoded a disk with FM or MFM, whereas an Apple II drive encodes disks with GCR, which, in terms of data density, is in between?

Yes. SD and DD really distinguish between FM and MFM encoding
techniques, and do not apply to Woz's methods of GCR encoding. 48TPI is
the thing that all of these notions of "single/double density" share in
common.

> Was GCR chosen because MFM encoding wasn't a viable or economical option at the time, and it was a higher-density method than FM? And why not 40 tracks (which would have yielded 160K per side with DOS 3.3) instead of 35? Same reason?

Economy of chips in the Disk II subsystem, like pretty much all
decisions that Woz made. It was, electronically speaking, radically
simpler than contemporary Shugart-based designs.

Remember too that the Disk II design went through a couple of firmware
revisions (13 vs. 16 sector) that implemented different GCR encoding
techniques (5 and 3 vs. 6 and 2). We could probably call those "single
density" and "double density," except they were not a doubling of
capacity... ;-)

[Patrick Schaefer]

Am 06.06.2013 19:22 schrieb slickr...@gmail.com:

> So, were they single density or double density drives?

Woz used GCR, which is comparable to double density (the technical word
is "modified frequency modulation", MFM).

> Did single-density disks even exist,

No. This is marketing gibberish. A FM signal consists of a clock bit and
a data bit, a MFM signal uses combined clock and data bits and stores
two of them in the same area. So from the magnetic disk's point of view
there is absolutely no difference.


Patrick

[Michael Black]

On Thu, 6 Jun 2013, iv...@ivanexpert.com wrote:

> Was GCR chosen because MFM encoding wasn't a viable or economical option
> at the time, and it was a higher-density method than FM? And why not 40
> tracks (which would have yielded 160K per side with DOS 3.3) instead of
> 35? Same reason?
>
>

Early drives, as I said in another post, were 35 tracks. Even when I got
a Radio Shack Color Computer in 1984, the standard disk controller was set
for 35 tracks, though I guess by then most drives were 40 track. YOu had
to patch the ROM to get the use of 40 tracks.

So I'm pretty sure that there wasn't the option of 40 tracks when Apple
first came out with their floppy disk system. I have no idea why there
wsa no later upgrade, other than perhaps they didn't want two standards
floating around. Or maybe, since standard Apple II drives were custom
made, Apple never changed the specs.

As for GCR, we were talking about that some weeks back. Woz cooked up a
scheme that used little hardware (the board on the drive is much simpler,
the controller board in the Apple II is pretty simple, not needing some
big and expensive IC at the time) that resulted in a much lower cost for
Apple at the time. At the time, even the dedicated floppy controller ICs
required lots of extra parts, making them expensive and bulky.

Michael

[barrym95838]

It's been many years since I fired up my old Franklin, but I seem to remember that it had a modified DOS 3.3 system master (called FDOS, I think) that, among other things, allowed the internal drives to read and write 35-track and 40-track disks seamlessly. What I never discovered is whether or not the standard Disk ][ drives were able to position their heads as far in as the internal Franklin drives. I suppose that I could have tried booting the modified system master on my //e, but I never did, for some reason. It might have been a good reason, but I just don't remember.

Mike

[Michael Black]

That's interesting. The Apple drives may have been able to do 40 tracks,
perhaps it was easier to just use the same drives minus the controller
board that were standard. Who knows.

I mentioned that the Radio Shack controller for the Color Computer only
did 35 tracks, and it also only did single side. So there were various
third party ROMs to make better use of the better drives. I used
something that turned out to be unlike the rest (or unlike what Radio
Shack went to when they finally adapted to the newer drives). I can't
remember what was standard, see the floppy as one single unit so the files
were spread over both sides, or treat it as two single sided drives. I
think the former was standard. Anyway, the ROM I used was the
non-standard.

So I have a few years of files using that odd setup. And the ROM is
actually an eprom lying around somewhere, I have no idea if it's still
good. And the ROM only works with the original CoCo, not the III. SO I
hvae to dig through layers if I want to get at them, and then no easy way
to transfer them. I think a few of those files would be nice to have.

But the point is, there were various schemes in those days by various
companies to get more onto the floppies, and they were fine, until you
wanted to use the floppies to transfer files, at which point the extra
and thus incompatible space became a liability.

Michael

[mdj]

On Friday, 7 June 2013 13:00:36 UTC+10, Michael Black wrote:

> That's interesting. The Apple drives may have been able to do 40 tracks,
>
> perhaps it was easier to just use the same drives minus the controller
>
> board that were standard. Who knows.

The mechanisms used by Apple are physically limited to 35 tracks*. 40 tracks works just fine with capable drives with modest patching of the operating system, but did not become widespread due to the inherent incompatibility with the vastly more common official drives.

* In practice the Apple drives can do 36 tracks. Some copy protection mechanisms used this little known fact. I'm unsure whether this was particular to the ALPS mechanisms or worked with the Shugart Disk ][ as well, but I assume it did.

Matt

[Egan Ford]

On 6/6/13 3:25 PM, Patrick Schaefer wrote:
>> Did single-density disks even exist,
>
> No. This is marketing gibberish.

What came first? The single or double density disk? Perhaps double is
the "marketing gibberish". :-)

Picture of one of my "labeled as" single-density disks:
http://asciiexpress.net/files/singleden.png

[retrogear]

On Thursday, June 6, 2013 11:56:56 PM UTC-5, mdj wrote:
> On Friday, 7 June 2013 13:00:36 UTC+10, Michael Black wrote: > That's interesting. The Apple drives may have been able to do 40 tracks, > > perhaps it was easier to just use the same drives minus the controller > > board that were standard. Who knows. The mechanisms used by Apple are physically limited to 35 tracks*. 40 tracks works just fine with capable drives with modest patching of the operating system, but did not become widespread due to the inherent incompatibility with the vastly more common official drives. * In practice the Apple drives can do 36 tracks. Some copy protection mechanisms used this little known fact. I'm unsure whether this was particular to the ALPS mechanisms or worked with the Shugart Disk ][ as well, but I assume it did. Matt

The way I remember it was I had Apple II drives that were Tandon mechanism and would only read 35 tracks. I had a Micro-Sci drive that was a Shugart mechanism that I was able to modify Dos 3.3 to do 40 tracks. Again, that was 20+ years ago so fuzzy at best... Larry

[David Schmidt]

That's right... the original mechanism specification only required
movement through 35 tracks; I've had early floppy media with some
characteristics like smaller access windows and smaller writable area
that would not allow head movement through 40 tracks. Time passed, and
media and mechanisms all supported 40 tracks - but OSes on the Apple II
side never expanded to take advantage of it.

Of course as mentioned earlier, changing horses mid-stream makes for
incompatibilities. And Apple already had a couple under its belt...
13/16 sectors, DOS/ProDOS.

[Sean Fahey]

On Friday, June 7, 2013 8:28:00 AM UTC-5, schmidtd wrote:

> That's right... the original mechanism specification only required
> movement through 35 tracks; I've had early floppy media with some
> characteristics like smaller access windows and smaller writable area
> that would not allow head movement through 40 tracks. Time passed, and
> media and mechanisms all supported 40 tracks - but OSes on the Apple II
> side never expanded to take advantage of it.

Diskettes finally got cheap enough that only the stingiest of users cared about cramming as much data as possible on them. Later on, everyone I knew who ever used 40 tracks to backup their hard drives ended up regretting it eventually.

I recall my first 3 disks cost me a months allowance and chore money. I'm kinda glad I wasn't old enough to start dating yet or I'd have been using cassettes for a few more years. Girlfriends were even more expensive.

[Michael Black]

I still have the bill for the first box of 10 floppy disks I bought, in
1984, it's just under fifty dollars here in Canada. Of course, that was
name brand, "Elephant" if I remember. I admit I was worried, so I didn't
buy the outright cheapest, though I can't remember if generic floppies
were out there yet.

It bugged me that I'd just bought a floppy disk drive and controller, and
they hadn't bothered tossing in a blank floppy so I could get going right
away. I seem to recall buying a pack of 2 floppy disks first, so I had
something until I spent more money.

I'd say capacity was an issue. With my Radio Shack COlor Computer, I
found a single 360K floppy a tad small. I was running Microware OS-9, and
I found I had to make multiple boot disks, have the operating system on
more than one disk, and then say games added to one, development added to
another, writing to another. I forget exactly, but the operating system
("unix-like") took up enough space that I had to trim in order to add
other things. And then the second floppy drive, when I got it (at a much
ower price than the first one), was used for my own files, like text and
assembler files.

I well remember when I got a 3.5" floppy drive, wham double the capacity.
So I could put everything I wanted on one disk, OS-9 and the C Compiler
and the text editing stuff. It was suddenly "like a hard drive", large
enough that I didn't hve to change disks.

What a different world it was.

Michael

[Michael J. Mahon]

Right. The Shugart 390 drive was the first Apple drive, and the cam used
for head positioning was guaranteed good for 35 tracks, and could actually
do 36 tracks (yes, there were early DOS mods for that ;-).

Later drives were made with positioned that could do 40 tracks, and the
media was capable of reliable use on those shorter inner tracks. But for
only a few percent improvement in capacity, you had to deal with 1) older,
incompatible drives, 2) older, less reliable media, and 3) the continued
need to use the lowest common denominator 35 track standard for disks that
are distributed.

All things considered, not worth the trouble. (Maybe Apple learned from the
lengthy 13-sector to 16-sector transition, when there were many fewer Apple
II's.)

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon

[Michael J. Mahon]

And Woz's controller is capable of FM (or single-density) operation--in
fact the address fields are encoded as FM, or 4+4 encoding.

GCR was a nice improvement in data density resulting from using
single-density bit resolution in a cleverer scheme made possible by Woz's
software data encoding/decoding (a scheme later improved from 5+3 to 6+2,
for even better data density.

[slickr...@gmail.com]

[slickr...@gmail.com]

On Friday, June 7, 2013 9:39:03 AM UTC-5, Michael Black wrote:

> On Fri, 7 Jun 2013, Sean Fahey wrote:
>
>
> >
>
> > I recall my first 3 disks cost me a months allowance and chore money.
>
> > I'm kinda glad I wasn't old enough to start dating yet or I'd have been
>
> > using cassettes for a few more years. Girlfriends were even more
>
> > expensive.
>
> >
>
> I still have the bill for the first box of 10 floppy disks I bought, in
>
> 1984, it's just under fifty dollars here in Canada. Of course, that was
>
> name brand, "Elephant" if I remember. I admit I was worried, so I didn't
>
> buy the outright cheapest, though I can't remember if generic floppies
>
> were out there yet.
>
>
>
> It bugged me that I'd just bought a floppy disk drive and controller, and
>
> they hadn't bothered tossing in a blank floppy so I could get going right
>
> away. I seem to recall buying a pack of 2 floppy disks first, so I had
>
> something until I spent more money.
>

How quickly things changed. When I entered the disk market just four years later, it was $10-20 for a 10-pack. That would remain pretty stable until the mid-1990s when the prices started coming down and you started being able to get a 50-pack of 3.5" disks for $20-25. I think the last time I looked a 50-pack now costs about $14, which is even cheaper when you factor in inflation. The price of most things has doubled since then.

[Sean Fahey]

On Tuesday, June 11, 2013 11:09:54 AM UTC-5, slickr...@gmail.com wrote:

> I think the last time I looked a 50-pack now costs about $14, which is even > cheaper when you factor in inflation. The price of most things has doubled > since then.

That's how it is with most disk-continued products.

[Michael J. Mahon]

Sean, I can always count on you to act like a groan man. ;-)

-michael (http://home.comcast.net/~mjmahon)

[Bill Garber]

"Michael J. Mahon" <mjm...@aol.com> wrote in message
news:518949984392673333.2...@news.giganews.com...

Careful... We don't want to become ][ snide... LOL 8>)

Bill Garber
http://www.sepa-electronics.com

[Michael Black]

On Tue, 11 Jun 2013, slickr...@gmail.com wrote:


> How quickly things changed. When I entered the disk market just four
> years later, it was $10-20 for a 10-pack. That would remain pretty
> stable until the mid-1990s when the prices started coming down and you
> started being able to get a 50-pack of 3.5" disks for $20-25. I think
> the last time I looked a 50-pack now costs about $14, which is even
> cheaper when you factor in inflation. The price of most things has
> doubled since then.
>

The thing about history is it always seems longer when you're living it.
I seem to recall that that four year period was kind of long at the time,
but yes, now it's a blink.

I honestly don't remember much about buying floppy disks after that first
10 pack. I must have, and certainly at some point I decided generic disks
were okay, but it just became part of the landscape. I'd have to go
through the boxes of old floppies to get an idea of brand and maybe that
would bring back memories of cost.

I think I got one of those 50pack deals. I can't even remember when it
was, maybe early 2000's but I don't know, suddenly the Staples flyer had
floppy disks, 3.5", at a good price and I thought I'd better get some.
Either it was an extraordinary price, or I was thinking by then that they
might be disappearing. I think it was a box of 25, and then sometime
shortly after, a box of fifty was on sale, and that too was too good to
miss. And I've barely used them. It turned out by that point that I
wasn't going to use them for storage, or transporting small bits of
information, it was as boot disks for Linux. Wait, some of that was for
installing Linux, so I needed multiple floppies, but they could generally
be reused afterwards.

There was also that time I found about five zip disks in a box on the
sidewalk, and brought them home, deciding that might be useful. So I
started looking for a used zip drive. By the time I found one at a garage
sale for a price I was willing to pay, the need had passed. Cheap 1gig
USB flash drives had arrived, much handier. Then I kept finding zip
drives in the garbage, yet none of them were tempting at that point to
actually try one.

Some old technology is interesting from a collection point of view, but
I'm finding these days things that I really wished for at one point but
couldn't afford, then a period when I might find them used but that didn't
happen, to finding them used and cheap, and not being interested. A few
years back, I saw a good reel to reel tape recorder for ten dollars, and I
couldn't be bothered carrying it home. The appeal of the item was lost
when I no longer had a real use for it. Same with the 8track recorder
sitting next to it, only five dollars. That one was tempting, something
that was relatively rare back then, and thus a novelty, but in the end I
left them both.

Michael

[mdj]

On Wednesday, 12 June 2013 06:15:54 UTC+10, Michael J. Mahon wrote:

> > That's how it is with most disk-continued products.
>
> Sean, I can always count on you to act like a groan man. ;-)

That pun is its own reword.

[Scott Alfter]

In article <alpine.LNX.2.02.1...@darkstar.example.org>,

Michael Black <et...@ncf.ca> wrote:
>So I'm pretty sure that there wasn't the option of 40 tracks when Apple
>first came out with their floppy disk system. I have no idea why there
>wsa no later upgrade, other than perhaps they didn't want two standards
>floating around. Or maybe, since standard Apple II drives were custom
>made, Apple never changed the specs.

Given that the drives in the DuoDisk my parents bought new in 1985 was only
good for 38 tracks, the latter explanation seems likely.

_/_
/ v \ Scott Alfter (remove the obvious to send mail)
(IIGS( http://alfter.us/ Top-posting!
\_^_/ >What's the most annoying thing on Usenet?

[bpa...@bellsouth.net]

Please pardon my replying to a somewhat old post;
but there seem to be some unaddressed misconceptions about HD disks.

On Thursday, June 6, 2013 2:22:29 PM UTC-5, Michael Black wrote:
> Out of the box they had higher capacity 80 tracks per side, so that would
> double the capacity, and no hardware needed.
>
> I guess it was the 1.2meg 5.25" drives that had the faster rotation speed.
> But then the high density drives appeared, they had narrower tracks, which
> meant a need for narrower read/write heads, and a different makeup of the
> coating on the 5.25" floppies, which is why the HD floppies are not seen
> as reliable in double density drives.

AFAIK, they're all 300 RPM. The higher density writes are simply done at a faster rate.

Also, high-density does not refer to the track count. The 1200kiB (1.17MiB) IBM format disks are 15 (512 byte) sectors per track, instead of 9 sectors, in addition to being 80 tracks, instead of 40. (It was annoying that MS-DOS didn't allow writing 80 double-density tracks (720k) with those drives.)

HD microfloppies (aka 3.5", aka 90mm) are 80 tracks, just like their DD counterparts. It's all done with track density--18 (512 byte) sectors, yielding 1440kiB (1.41MiB). (How these came to be referred to as 1.44 meg, rather than 1.4 meg, is another conversation.) Apple opted to use the same logical format for HD as the MS/IBMoid world (as well as supporting the 720k format) for compatibility reasons.

The formulation of HD disks is different from DD, and requires different bias. This is why HD floppies are lousy to unusable as DD--much in the same way that metal-particle tapes perform badly on non metal-capable tape decks.

—Brian