Cassette Capacity
Mike Westerfield
and was remembering the good old days, when you could more or less
grasp how much stuff was on a disk. That led me to wonder how much
stuff was on the first storage device I ever used on an Apple II. Does
anyone recall about how much information could be stored on a cassette
tape on an Apple II? I realize it varied by tape size, so the
appropriate unit is probably bytes per minute.
Mike
mmphosis
resulted in typical data rates of 500 to 2000 bit/s, although some
games used special faster loading routines, up to around 4000-bit/s. A
rate of 2000-bit/s equates to a capacity of around 660 kilobytes per
side of a 90-minute tape."
http://en.wikipedia.org/wiki/Compact_Cassette#Data_recording
John B. Matthews
<f8b45024-498e-403d...@v15g2000prn.googlegroups.com>,
mmphosis <markw...@yahoo.com> wrote:
More data points: "However, [Apple's cassette interface] ran at 1200
baud (most microcomputer cassette interfaces in 1976 and 1977 ran at
only 300 baud) and was more consistently successful at getting a good
load into memory when compared to other computers of the day."
<http://apple2history.org/history/ah02.html>
"The tape moves at 4.76 cm/s (1 7/8 in/s) from left to right."
<http://en.wikipedia.org/wiki/Compact_Cassette>
I bought a few empty cassette shells and made a series of tapes, each
~10 minutes long and holding ~90 KB (a few small, related programs).
--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>
Albert D. Kallal
At the time, blank floppy disks where in the $7-9$ range for ONE floppy. I
had a floppy drive, but disks were expensive.
So, I grabbed a little relay from Radio Shack, and plugged that relay into
the cassette recorders' on/off jack (the smaller jack, right beside the
microphone in jack that most table top cassette recorders had).
I then just simply hit the play + record button, but the "pause" was now
controlled by the apple...
I then wrote some software to read sectors of the disk into memory (I about
40k of data), I would then start the tape, and do a bsave...when done, stop
the tape, and then continue reading in the next 40kb of data. I recall is
took 4 of these, but since it was automatic, I could pop in a disk, and walk
away...
I seem to recall that a 45 min tape, each side was good for a whole floppy
disk, but I was not using the full side of the cassette. Given that one
could purchase el-cheapo cassettes at discount stores for about 30 cents, it
was a heck of a lot cheaper to archive un-used floppy disks at $8 a piece...
I never was a hardware guy, but hooking in a simple relay into the game
(paddle) port, and a bit of software to read the floppy into memory and
start a bsave was quite easy. It was so easy to do, and it is this kind of
ease of accomplishing tasks that gives me such fond memories of my Apple
II+...
--
Albert D. Kallal
Edmonton, Alberta Canada
pleaseNOO...@msn.com
winston...@yahoo.com
That was how the TI-99's cassette worked, it controlled the motor in a
similar way. That allowed it to do cassette file operations as well.
However, it was still painful due to the pause between each set of
data, the "sync" part at the beginning of each record, and any padding
to the record (record lengths of only 64/128/192 bytes supported).
Michael J. Mahon
Apple cassette data rates are 1kbits/sec for 1s and 2kbits/sec for 0s.
If we assume that 1s and 0s are equally probable (though "typical"
uncompressed data tends to have more 0s than 1s), then the average
data rate is 1500bits/sec.
So one side of a C60 (the most common and most durable cassette) holds
30 minutes of recording, or 1800 seconds, or 2.7 megabits, or 337,500
bytes--if it contains only data.
But since each data "record" consists of ten seconds of "header"
tone, the fraction of a recording that actually consists of data
depends strongly on the length of data recorded in each record and
the blank space ("gap") that the user puts between records or groups
of records.
If we assume that a typical data record contains 10,000 bytes, it
takes 10 seconds for header and 53.3 seconds for data. Then if a
typical user leaves about 5 seconds of gap between records to
make record cueing easy, that would cause each record to take 68.3
seconds of tape.
With these assumptions, a full side of a C60 holds 260,000 bytes,
and both sides hold 520,000 bytes.
Of course, what is usually recorded on cassettes is BASIC programs,
and they consist of <user gap> <length record> <program record>,
where each record still has a 10-second header and the short length
record contains a negligible amount of data.
So a BASIC program of 10,000 bytes takes 5 seconds for user gap,
plus 20 seconds of header for two data records, plus 53.3 seconds
for the program, or 78.3 seconds of tape.
Under these assumptions, a C60 side holds almost 230,000 bytes, and
a whole cassette holds about 460,000 bytes.
As you can see, Apple cassettes are relatively capacious, particularly
in terms of cost per byte!
Of course, if short programs were recorded, then the effective
capacity would be much lower, since most of the tape would consist
of gaps and headers, with relatively little data.
For example, if we repeat the above calculations assuming a BASIC
program length of 2,000 bytes, then each side of a C60 would hold
only about 100,000 bytes.
BTW, cassettes longer than C60s are made of thinner tape, which makes
them more delicate and less reliable, and also increases the rate of
"print-through" between adjacent layers of tape wound on the spindle
for long periods. As a result, longer tapes are not recommended for
long-term data storage.
I've actually had good results with both C60s and C90s, and have found
both to be reliably readable after 28 years of storage. ;-)
-michael
NadaNet and AppleCrate II: parallel computing for Apple II computers!
Home page: http://home.comcast.net/~mjmahon
"The wastebasket is our most important design
tool--and it's seriously underused."
winston...@yahoo.com
>
> I've actually had good results with both C60s and C90s, and have found
> both to be reliably readable after 28 years of storage. ;-)
>
Try *that* with your CDs and DVDs!
Alex Freed
>
>> I've actually had good results with both C60s and C90s, and have found
>> both to be reliably readable after 28 years of storage. ;-)
>>
>
> Try *that* with your CDs and DVDs!
If you use the stone (as in a cave wall) as recording media and a piece
of flint as a recording tool the data retention rate has been shown to
be at least 20,000 years. Tooth marks on bone while not left there for
information storage remain for hundreds of millions of years.
Unfortunately high density recording methods have adverse effect on
longevity.
On a more serious note the pits on a "real" CD should be quite robust.
The CD-RW is likely a lot less so.
-Alex.
Michael J. Mahon
I agree completely.
My primary archival medium is at least two copies on recently-
manufactured hard disk drives, each of which is verified at least
once a year.
I find that any other medium is so much less convenient to use and to
verify that I do not verify them. Hard disks are now very cheap,
very dense, and very fast compared to the alternatives--and it's
trivial to migrate data to newer drives/interfaces every few years.
With 1.5TB SATA drives now regularly on sale for less than $90, it's
hard to justify any other medium.
mdj
> Alex Freed wrote:
> > winston19842...@yahoo.com wrote:
>
> >>> I've actually had good results with both C60s and C90s, and have found
> >>> both to be reliably readable after 28 years of storage. ;-)
>
> >> Try *that* with your CDs and DVDs!
>
> > If you use the stone (as in a cave wall) as recording media and a piece
> > of flint as a recording tool the data retention rate has been shown to
> > be at least 20,000 years. Tooth marks on bone while not left there for
> > information storage remain for hundreds of millions of years.
> > Unfortunately high density recording methods have adverse effect on
> > longevity.
>
> > On a more serious note the pits on a "real" CD should be quite robust.
> > The CD-RW is likely a lot less so.
>
> I agree completely.
>
> My primary archival medium is at least two copies on recently-
> manufactured hard disk drives, each of which is verified at least
> once a year.
>
> I find that any other medium is so much less convenient to use and to
> verify that I do not verify them. Hard disks are now very cheap,
> very dense, and very fast compared to the alternatives--and it's
> trivial to migrate data to newer drives/interfaces every few years.
>
> With 1.5TB SATA drives now regularly on sale for less than $90, it's
> hard to justify any other medium.
That's my strategy too. I run a pair of those in RAID1 and that stores
everything we need with room to spare.
Ideally I'd back up that set to another machine somewhere, but all
'critical' data is replicated on 2 laptops and my server in the US,
and the bulk of the data can be recreated in a weekend by reloading
the CD's etc.
Matt
Andy McFadden
> With 1.5TB SATA drives now regularly on sale for less than $90, it's
> hard to justify any other medium.
I don't know. At 1500bps, you can back up a gigabyte to cassette tape
in a little over two months. And at roughly 500KB per 60-minute cassette,
you'd only need a couple thousand of them.
--
Send mail to fad...@fadden.com (Andy McFadden) - http://www.fadden.com/
Fight Internet Spam - http://spam.abuse.net/spam/ & http://spamcop.net/
Nama
If Andys calculations are correct, then it's either one 1.5TB drive or
1,500,000 C60 tapes.
The cheapest C60 I could find was about $1, so that only comes to
$1,500,000. A bargain!
So I'm with Andy on this one...Cassette tapes seem like the way to
go.
winston...@yahoo.com
> Michael J. Mahon <mjma...@aol.com> wrote:
>
> > With 1.5TB SATA drives now regularly on sale for less than $90, it's
> > hard to justify any other medium.
>
> I don't know. At 1500bps, you can back up a gigabyte to cassette tape
> in a little over two months. And at roughly 500KB per 60-minute cassette,
> you'd only need a couple thousand of them.
>
Hmm. Now me wonders about the "wafertape" systems, like the stringy-
floppy thingy the TRS-80 people used, or the Coleco Adam's tape
systems...? I have an Adam, and the tape drive is actually quite
wonderful. Never did experience the "erase tape on power-on" problem
reported, and I didn't know better for about 6 months of using it...
Nama
oh...and only take 167 years to back up (not including the extra time
it takes to swap out 1,500,000 cassette tapes)
winston...@yahoo.com
I can get C30's for $0.35!
mdj
> Michael J. Mahon <mjma...@aol.com> wrote:
>
> > With 1.5TB SATA drives now regularly on sale for less than $90, it's
> > hard to justify any other medium.
>
> I don't know. At 1500bps, you can back up a gigabyte to cassette tape
> in a little over two months. And at roughly 500KB per 60-minute cassette,
> you'd only need a couple thousand of them.
And in this day and age, with accelerated Apple II's being the norm,
you can probably keep up with one of those fandangled cassette decks
that support high speed dubbing. Might even get the whole job done
within a standard lifetime...
As the saying goes, it's hard to beat a wagon full of backup tapes for
bandwidth, but the latency (particularly in this case) is a bitch :-)
Steven Nelson
> My primary archival medium is at least two copies on recently-
> manufactured hard disk drives, each of which is verified at least
> once a year.
>
> I find that any other medium is so much less convenient to use and to
> verify that I do not verify them. Hard disks are now very cheap,
> very dense, and very fast compared to the alternatives--and it's
> trivial to migrate data to newer drives/interfaces every few years.
>
> With 1.5TB SATA drives now regularly on sale for less than $90, it's
> hard to justify any other medium.
>
> -michael
The following post is in the spirit of fun and jest, with no
disparagement meant :
Michael, good advice, but I am having difficulty doing what you
suggest. How do you hook a 1.5TB drive up to an Apple ][ (IIe or
IIGS)? I can't find one with the 'right' connector! My interim
attempt at a solution involves putting the large drive on an iMac -
but how do I copy files over? I currently use an older PowerPC
running MacOS (7/8/9) with localtalk cabling and ethernet to a
router. Copy files over localtalk to the PowerPC and then copy the
files over to the iMac over ethernet. Slow but works. The PowerPC is
also running Localtalk Bridge, so the GS/OS Appleshare can 'see' the
iMac, but I can't get a 'login' connection to actually mount the iMac
drive on the GSOS Finder desktop. Drats!
To make matters worse, when I use a cassette for transfer medium, the
iMac doesn't load the files! Double drats!
So, backing up an Apple][ to a cassette tape seems to be the better
solution until Apple develops the OSX opsys and hardware to use the
more robust medium (tape cassette), irregardless of storage costs.
$0.02
Have a great day!
--Steve
D Finnigan
An amusing suggestion which I read of awhile back was to use an iPod to
store cassette tapes such that you'd plug a mini-plug from the iPod's
headphone jack in to the Apple's cassette-in port and start the "song"
playing on the iPod.
Now with the newer iPods which can also record from that same headphone
jack, we can make "cassettes" on the iPod and also play them back with a
Y-splitter cable.
Michael Black
> Michael J. Mahon <mjm...@aol.com> wrote:
>> With 1.5TB SATA drives now regularly on sale for less than $90, it's
>> hard to justify any other medium.
>
> I don't know. At 1500bps, you can back up a gigabyte to cassette tape
> in a little over two months. And at roughly 500KB per 60-minute cassette,
> you'd only need a couple thousand of them.
>
But you can probably get those cassettes for free, or close to it. After
all, nobody much uses cassettes anymore, and they want to get rid of
what they have.
A few years ago, I came upon a bunch of boxes of cassettes, not bottom of
the line either, waiting for the garbage. They'd been used, but looked
in good shape. I only took one box of ten, I couldn't figure out what
I might need them for (since I already have a stock of cassettes, and
would have more if I ever got around to copying the ones I recorded
on to digital.
The reality is, I never tried to cram computer programs onto cassette
tapes (and I didn't get a floppy drive till 1984, and my first hard
drive till 1993). It was too much bother to find a specific program
some programs into the tape. So I tended to use a tape for development,
keeping subsequent saves for subsequent versions, and then move the
finished work to some other tape. For the most common programs, I
used those ten minute cassettes, Radio Shack sold them back then so
you didn't need to make your own, and would put one or two programs
on them. Yes, a waste, but the audio cassette version of a "module"
that came later.
Michael
Michael Black
The thing about those wasn't just the medium, but they were treated
as a "cheap floppy drive". So there was a real operating system
involved, and the computer did the work to find the required program
and load it, albeit slower than a floppy drive. Cassettes, you generally
did have to keep track on paper of the sequence of the programs on
the tape, and even the counter reading when each started. The Stringy
Floppy or wafertapes, unlike the cheap cassette recorders commonly used
with computers back then, had some advanced drive that was intended
for computer control, so it was much easier to control from the
computer. Even the Commodore PET, that had a built in
cassette recorder, that was a standard recorder built into the computer,
not some fancy drive.
On the other hand, there was in the early days one floppy disk system
that did away with the operating system. It was a hybrid of cassette
and floppy, in that you'd simply write the program to the floppy, and
then write down where it started and ended.
Michael
Gust L Friedemann
Someone else may want to chime in on this as well, but I seem to recall
getting about 100,000 bytes per 60 minute cassette. Or roughly 13kb per
60 min. Simple math will give you the per minute conversion, if you
really need it. :)
I may be recalling the Commodore and Atari data-cassettes, though.
Someone else, please back me up on this, if this is valid memeory. :)
Gust L Friedemann
Gust L Friedemann
Gust L Friedemann
Gust L Friedemann
Someone else may want to chime in on this as well, but I seem to recall
Gust L Friedemann
Someone else may want to chime in on this as well, but I seem to recall