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Re: What did an original Apple II sell for? [message #352148 is a reply to message #352088] |
Sun, 10 September 2017 11:53 |
barrym95838
Messages: 130 Registered: April 2013
Karma: 0
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On Friday, September 8, 2017 at 8:40:52 PM UTC-7, I am Rob wrote:
> On Tuesday, September 5, 2017 at 9:39:35 PM UTC-6, I am Rob wrote:
>> Just posting this for a comparison.
>>
>> http://www.ebay.com/itm/Commodore-65-Computer-The-Holy-Grail -of-Commodore-Collecting/222630201237?_trkparms=aid%3D777003 %26algo%3DDISCL.MBE%26ao%3D1%26asc%3D43628%26meid%3Df4210064 9261499fb51d654c9cf23091%26pid%3D100013%26rk%3D5%26rkt%3D12% 26mehot%3Dpp%26sd%3D222322359951&_trksid=p2047675.c10001 3.m1986
>
>
> Final price: $18,350.00
http://oldcomputers.net/appleii.html
A new 4K Apple ][ sold for $1298 in 1977, which inflates to about $5,243
in 2017. I think that 4K would feel a bit constrictive even back then,
and 16K was probably a more popular choice at $1698 ($6858), at least
until the Disk ][ was introduced.
Mike B.
Mike B.
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Re: What did an original Apple II sell for? [message #352348 is a reply to message #352148] |
Wed, 13 September 2017 09:44 |
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Originally posted by: cb meeks
On Sunday, September 10, 2017 at 11:54:00 AM UTC-4, barrym95838 wrote:
> On Friday, September 8, 2017 at 8:40:52 PM UTC-7, I am Rob wrote:
>> On Tuesday, September 5, 2017 at 9:39:35 PM UTC-6, I am Rob wrote:
>>> Just posting this for a comparison.
>>>
>>> http://www.ebay.com/itm/Commodore-65-Computer-The-Holy-Grail -of-Commodore-Collecting/222630201237?_trkparms=aid%3D777003 %26algo%3DDISCL.MBE%26ao%3D1%26asc%3D43628%26meid%3Df4210064 9261499fb51d654c9cf23091%26pid%3D100013%26rk%3D5%26rkt%3D12% 26mehot%3Dpp%26sd%3D222322359951&_trksid=p2047675.c10001 3.m1986
>>
>>
>> Final price: $18,350.00
>
> http://oldcomputers.net/appleii.html
>
> A new 4K Apple ][ sold for $1298 in 1977, which inflates to about $5,243
> in 2017. I think that 4K would feel a bit constrictive even back then,
> and 16K was probably a more popular choice at $1698 ($6858), at least
> until the Disk ][ was introduced.
>
> Mike B.
>
> Mike B.
Sure, 4K would have been restrictive. But, you have to remember that in 1977 people actually didn't know what to do with a computer and there wasn't exactly a lot of software. I would guess that most people brought their 4K Apple II home and said "Now what?".
It was a chick-n-egg problem. People needed more RAM for better software but they needed better software to justify more RAM. :-)
That why it took a few years actually before computer started selling VERY well.
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Re: What did an original Apple II sell for? [message #352381 is a reply to message #352348] |
Wed, 13 September 2017 19:06 |
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Originally posted by: R.Kiefer.SPAEM
cb meeks wrote:
> Sure, 4K would have been restrictive. But, you have to remember that in
> 1977 people actually didn't know what to do with a computer and there
> wasn't exactly a lot of software. I would guess that most people brought
> their 4K Apple II home and said "Now what?".
At that time I started my "career" in school in front of a PET with 8kB
of RAM and the tape recorder. After some months we felt this
restriction. We just "played" with our own BASIC programs.
- Ralf
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Re: What did an original Apple II sell for? [message #352389 is a reply to message #352381] |
Thu, 14 September 2017 00:37 |
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Originally posted by: Chris Tobar
This is slightly off topic, but what Ralf said about using a PET with a tape recorder made me curious - was it hard to get cassette tapes to work for saving and loading data back then?
When I bought my Apple II+ a few months ago, I briefly tried to save programs to a tape before I found some blank floppy disks. It drove me nuts! It was so finicky, I kept getting error messages and had to keep adjusting the volume. I only got it to work once or twice. Are Apple II computers just more picky, or was this a common problem with early computers?
- Chris
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Re: What did an original Apple II sell for? [message #352390 is a reply to message #352389] |
Thu, 14 September 2017 01:28 |
barrym95838
Messages: 130 Registered: April 2013
Karma: 0
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Senior Member |
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On Wednesday, September 13, 2017 at 9:37:04 PM UTC-7, Chris Tobar wrote:
> This is slightly off topic, but what Ralf said about using a PET with a tape recorder made me curious - was it hard to get cassette tapes to work for saving and loading data back then?
>
> When I bought my Apple II+ a few months ago, I briefly tried to save programs to a tape before I found some blank floppy disks. It drove me nuts! It was so finicky, I kept getting error messages and had to keep adjusting the volume. I only got it to work once or twice. Are Apple II computers just more picky, or was this a common problem with early computers?
>
> - Chris
I used tapes for storage in the early 1980s on the Apple ][, C=64, and TRS-80. In my personal experience, I would grade them at "B", "C", and "D" respectively, for overall performance and reliability. As soon as I could afford the Disk ][, I was completely done with Apple cassettes ... the difference was night and day.
Mike B.
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Re: What did an original Apple II sell for? [message #352391 is a reply to message #352390] |
Thu, 14 September 2017 02:36 |
Your Name
Messages: 910 Registered: September 2013
Karma: 0
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Senior Member |
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On 2017-09-14 05:28:26 +0000, barrym95838 said:
> On Wednesday, September 13, 2017 at 9:37:04 PM UTC-7, Chris Tobar wrote:
>>
>> This is slightly off topic, but what Ralf said about using a PET with a
>> tape recorder made me curious - was it hard to get cassette tapes to
>> work for saving and loading data back then?
>>
>> When I bought my Apple II+ a few months ago, I briefly tried to save
>> programs to a tape before I found some blank floppy disks. It drove me
>> nuts! It was so finicky, I kept getting error messages and had to keep
>> adjusting the volume. I only got it to work once or twice. Are Apple II
>> computers just more picky, or was this a common problem with early
>> computers?>> - Chris
>
> I used tapes for storage in the early 1980s on the Apple ][, C=64, and
> TRS-80. In my personal experience, I would grade them at "B", "C", and
> "D" respectively, for overall performance and reliability. As soon as
> I could afford the Disk ][, I was completely done with Apple cassettes
> ... the difference was night and day.
I can't recall ever having many issues with the tapes on our VIC20 and
C64 computers ... other than being horribly slow of course. Things did
speed up a bit when "turbo loaders" started appearing. We did
eventually get a disk drive for the C64 though and the tape drive was
"put out to pasture" (the games still on tape were transferred to disk
using one of those "freeze" cartridges that were a fad at one time).
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Re: What did an original Apple II sell for? [message #352392 is a reply to message #352389] |
Thu, 14 September 2017 03:20 |
Michael J. Mahon
Messages: 1767 Registered: October 2012
Karma: 0
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Senior Member |
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Chris Tobar <gatewaycityca@yahoo.com> wrote:
> This is slightly off topic, but what Ralf said about using a PET with a
> tape recorder made me curious - was it hard to get cassette tapes to work
> for saving and loading data back then?
>
> When I bought my Apple II+ a few months ago, I briefly tried to save
> programs to a tape before I found some blank floppy disks. It drove me
> nuts! It was so finicky, I kept getting error messages and had to keep
> adjusting the volume. I only got it to work once or twice. Are Apple II
> computers just more picky, or was this a common problem with early computers?
>
> - Chris
>
My experience is that cassette storage is quite easy and reliable on the
Apple II.
The key is using a "simple" cassette recorder, without tone conttols.
Simple recorders about 6"x12"x2" were very common in the eighties, before
the Walkman form factor.
Typically, a mid- to two-thirds-volume setting was about right.
It was necessary to pay attention to head alignment (azimuth) if cassettes
were interchanged between decks, but problems were pretty rare. This is not
an issue if only one deck is used.
Proper tape handling technique was important.
I generally used C60s, marching down the tape as I saved subsequent
revisions of a program, and as I wrote new programs. The tape counter was
religiously zeroed at the start of each cassette, and the counter was
written down on an ascending log of the tape's contents.
To record, write down the tape counter, press PLAY-RECORD and press ENTER
for the save command. Listen for the end of the data, wait a couple of
seconds, and press STOP on the recorder.
To read, position the tape to the logged number, press PLAY, and when you
hear the "preface" tone, press ENTER for the load command. When the data
ends, wait a couple of seconds and press STOP.
To simplify the cuing and avoid the use of headphones, I soldered a 220 Ohm
resistor across the speaker cut-out switch on the "line out" jack of the
deck. That caused all playback and monitor audio to be audible through the
deck's speaker at low volume--perfect for cueing.
I very seldom encountered a data recording error (maybe twice in over ten
*hours* of data), but, since I recorded all revisions of my code/data, it
was not difficult to recover using the previous version.
Something that may help (I tried it as a verification strategy) is to write
a short assembler program that simply "echoes" the cassette input to the
Apple speaker. Varying the playback volume while such a loop is running
provides instant feedback on whether the cassette input port is "hearing"
the data. The level should be somewhat higher that the lowest level that is
reproduced correctly.
Of course, disks are much faster and more convenient, but reliability and
usability were excellent if an appropriate deck and use protocol were used.
The Apple cassette interface is very robust.
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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Re: What did an original Apple II sell for? [message #352393 is a reply to message #352390] |
Thu, 14 September 2017 08:10 |
Richard Thiebaud
Messages: 222 Registered: May 2013
Karma: 0
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Senior Member |
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On 09/14/2017 01:28 AM, barrym95838 wrote:
> On Wednesday, September 13, 2017 at 9:37:04 PM UTC-7, Chris Tobar wrote:
>> This is slightly off topic, but what Ralf said about using a PET with a tape recorder made me curious - was it hard to get cassette tapes to work for saving and loading data back then?
>>
>> When I bought my Apple II+ a few months ago, I briefly tried to save programs to a tape before I found some blank floppy disks. It drove me nuts! It was so finicky, I kept getting error messages and had to keep adjusting the volume. I only got it to work once or twice. Are Apple II computers just more picky, or was this a common problem with early computers?
>>
>> - Chris
>
> I used tapes for storage in the early 1980s on the Apple ][, C=64, and TRS-80. In my personal experience, I would grade them at "B", "C", and "D" respectively, for overall performance and reliability. As soon as I could afford the Disk ][, I was completely done with Apple cassettes ... the difference was night and day.
>
> Mike B.
>
I used tapes with my TRS-80 and they worked well. My brother used tapes
with his Apple II and they were finicky.
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Re: What did an original Apple II sell for? [message #352405 is a reply to message #351959] |
Thu, 14 September 2017 09:56 |
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Originally posted by: Jorge
A floppy rotates @300 rpm, a track has 16 sectors, a sector 256 bytes, a byte 8 bits => a bit is read roughly every 1/(300/60)/16/256/8 -> 6µs
On the tape a one takes 1000µs and a zero 500µs, so loading a bit takes 750µs on average.
600 dollars (1978 dollars!) bought you a 125x boost in speed, and that alone was a good thing.
But the cassette driver could run much faster today because we don't use cassettes any more. I think 100..200 µs per bit could be made to work error free nowadays, that's 3..7 times faster. That's something ADTPro could use... Oliver? David? The Schmidts? Do you hear me? :-)
I once peeked with the scope at the signal coming out of the 741 of the cassette input, it had a rise time of 20 to 30 ms. And it takes quite longer to react in one direction that in the other (from low to high IIRC). That's something to keep in mind.
A problem of the cassette output of the Apple II is R19 (12k), all the Apple IIs I have had have that R shorted with a wire with test clips to make it compatible with the audio line input of the Macs. Works wonderfully! BTW this is also something the ADTPro user guide should mention because a Mac can't sense properly the Apple II microphone-level signal and that totally ruins ADTPro audio transfers for Mac users.
--
Jorge.
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Re: What did an original Apple II sell for? [message #352413 is a reply to message #352405] |
Thu, 14 September 2017 11:03 |
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Originally posted by: R.Kiefer.SPAEM
Jorge wrote:
> A floppy rotates @300 rpm, a track has 16 sectors, a sector 256 bytes, a
> byte 8 bits => a bit is read roughly every 1/(300/60)/16/256/8 -> 6µs
Don't forget the gaps! A single track (DD, MFM) covers 6500Byte =
52.000bits.
-> one bit is represented in ˜4usec.
> On the tape a one takes 1000µs and a zero 500µs, so loading a bit takes
> 750µs on average.
See Kansas City standard. But Apple used their own standard.
https://en.wikipedia.org/wiki/Kansas_City_standard
My Eltec Eurocom 1 uses the 6850 @300Baud to generate the raw data
stream for the tape recorder. But there is a coding in the files with
overhead. My Eurocom 1 doesn't store raw binaries but Motorola S-Records
- Ralf
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Re: What did an original Apple II sell for? [message #352414 is a reply to message #352405] |
Thu, 14 September 2017 11:11 |
David Schmidt
Messages: 993 Registered: October 2012
Karma: 0
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Senior Member |
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On 9/14/2017 9:56 AM, Jorge wrote:
> [...]
> But the cassette driver could run much faster today because we don't use cassettes any more. I think 100..200 µs per bit could be made to work error free nowadays, that's 3..7 times faster. That's something ADTPro could use... Oliver? David? The Schmidts? Do you hear me? :-)
Also see: https://github.com/datajerk/c2t
> [...]
> A problem of the cassette output of the Apple II is R19 (12k), all the Apple IIs I have had have that R shorted with a wire with test clips to make it compatible with the audio line input of the Macs. Works wonderfully! BTW this is also something the ADTPro user guide should mention because a Mac can't sense properly the Apple II microphone-level signal and that totally ruins ADTPro audio transfers for Mac users.
Normally, Mac users do the mic boost as suggested on the ADTPro website:
http://adtpro.com/connectionsaudio.html#Boosting
Are you saying you bridge the resistor and it essentially boosts the
output at the Apple II end?
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Re: What did an original Apple II sell for? [message #352415 is a reply to message #352413] |
Thu, 14 September 2017 11:15 |
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Originally posted by: Jorge
On Thursday, September 14, 2017 at 5:03:06 PM UTC+2, Ralf Kiefer wrote:
> Jorge wrote:
>
>> A floppy rotates @300 rpm, a track has 16 sectors, a sector 256 bytes, a
>> byte 8 bits => a bit is read roughly every 1/(300/60)/16/256/8 -> 6µs
>
>
> Don't forget the gaps! A single track (DD, MFM) covers 6500Byte =
> 52.000bits.
> -> one bit is represented in ˜4usec.
But that's raw/unformatted, my figure takes the encoding/protocol into account :-)
>> On the tape a one takes 1000µs and a zero 500µs, so loading a bit takes
>> 750µs on average.
>
> See Kansas City standard. But Apple used their own standard.
> https://en.wikipedia.org/wiki/Kansas_City_standard
>
> My Eltec Eurocom 1 uses the 6850 @300Baud to generate the raw data
> stream for the tape recorder. But there is a coding in the files with
> overhead. My Eurocom 1 doesn't store raw binaries but Motorola S-Records
So that's even worse yet! Apple's baud rate is 1333 (1/750e-6).
Cheers,
--
Jorge.
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Re: What did an original Apple II sell for? [message #352416 is a reply to message #352414] |
Thu, 14 September 2017 11:27 |
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Originally posted by: Jorge
On Thursday, September 14, 2017 at 5:11:16 PM UTC+2, schmidtd wrote:
>
> Are you saying you bridge the resistor and it essentially boosts the
> output at the Apple II end?
Yes.
I totally missed the paragraph "On the OSX operating system, you will find the microphone boost by opening the Audio-MIDI configuration tool, selecting the setting for line-in, and then moving the volume sliders all the way to the right" :-)
But, hey, if you short r19 you don't need to do that AND... you can pass programs between Apple IIs via the cassette ports, something you can't do if you don't (for the same reason).
--
Jorge.
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Re: What did an original Apple II sell for? [message #352418 is a reply to message #352393] |
Thu, 14 September 2017 12:01 |
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Originally posted by: Jorge
On Thursday, September 14, 2017 at 2:10:36 PM UTC+2, Richard Thiebaud wrote:
>>
> I used tapes with my TRS-80 and they worked well. My brother used tapes
> with his Apple II and they were finicky.
That was my experience too, trash-80's tapes worked better, were more reliable, it was less picky than the Apple II.
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Re: What did an original Apple II sell for? [message #352419 is a reply to message #352405] |
Thu, 14 September 2017 12:29 |
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Originally posted by: Jorge
On Thursday, September 14, 2017 at 3:56:44 PM UTC+2, Jorge wrote:
>
> I once peeked with the scope at the signal coming out of the 741 of the cassette input, it had a rise time of 20 to 30 ms. And it takes quite longer to react in one direction that in the other (from low to high IIRC). That's something to keep in mind.
>
A picture is worth a thousand words: https://imgur.com/a/K2IeH
The yellow trace is H14 (74251) pin 4, the blue trace is the 741 pin 2 (cassette input). R19 is shorted and there's a jack to jack cable feeding the cassette output into the cassette input.
--
Jorge
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Re: What did an original Apple II sell for? [message #352420 is a reply to message #352419] |
Thu, 14 September 2017 12:55 |
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Originally posted by: Jorge
On Thursday, September 14, 2017 at 6:29:28 PM UTC+2, Jorge wrote:
> On Thursday, September 14, 2017 at 3:56:44 PM UTC+2, Jorge wrote:
>>
>> I once peeked with the scope at the signal coming out of the 741 of the cassette input, it had a rise time of 20 to 30 ms. And it takes quite longer to react in one direction that in the other (from low to high IIRC). That's something to keep in mind.
>>
>
> A picture is worth a thousand words: https://imgur.com/a/K2IeH
>
> The yellow trace is H14 (74251) pin 4, the blue trace is the 741 pin 2 (cassette input). R19 is shorted and there's a jack to jack cable feeding the cassette output into the cassette input.
What is interesting there is that the same 82µs pulse, depending on its polarity, can result in either a 65µs or an 85µs pulse at $c060 (the yellow trace). It can happen to be shortened or elongated.
--
Jorge.
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Re: What did an original Apple II sell for? [message #352429 is a reply to message #352425] |
Thu, 14 September 2017 14:52 |
Antoine Vignau
Messages: 1860 Registered: October 2012
Karma: 0
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Senior Member |
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Jorge,
your calculation for the number of bytes for a sector is wrong. We save nibbles not bytes, so 342 nibbles to handle 256 sectors. At the speed of 300RPM, it is roughly 4us per bit.
I let you perform the calculation of the number of data we can have per track...
Antoine
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Re: What did an original Apple II sell for? [message #352437 is a reply to message #352429] |
Thu, 14 September 2017 15:21 |
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Originally posted by: Jorge
On Thursday, September 14, 2017 at 8:52:51 PM UTC+2, Antoine Vignau wrote:
> Jorge,
> your calculation for the number of bytes for a sector is wrong. We save nibbles not bytes, so 342 nibbles to handle 256 sectors. At the speed of 300RPM, it is roughly 4us per bit.
>
To use a serial port analogy, you're talking bauds I'm talking bps. But you knew that already...
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Re: What did an original Apple II sell for? [message #352438 is a reply to message #352405] |
Thu, 14 September 2017 17:03 |
Michael J. Mahon
Messages: 1767 Registered: October 2012
Karma: 0
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Senior Member |
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Jorge <jorge@jorgechamorro.com> wrote:
> A floppy rotates @300 rpm, a track has 16 sectors, a sector 256 bytes, a
> byte 8 bits => a bit is read roughly every 1/(300/60)/16/256/8 -> 6µs
>
> On the tape a one takes 1000µs and a zero 500µs, so loading a bit takes 750µs on average.
>
> 600 dollars (1978 dollars!) bought you a 125x boost in speed, and that
> alone was a good thing.
Consider, though, the actual effect on "user speed".
When I was developing Applesoft code (not unusual for 1980 ;-), I would
rewind the cassette deck to the start of the last-SAVEd version and LOAD
it. This would typically take a minute or less.
Then I would edit and test the program for a session lasting an hour or
two, then I would SAVE the new version after the old one--another minute.
If, during the session, I made a big change (a new fork), I might SAVE one
or two times within a sesssion.
In any case, the few minutes spent LOADing and SAVEing was a minuscule part
of my time at the computer.
My first exposure to a disk-based Apple was actually just a two-month
rental, to developed a piece of software. I certainly enjoyed the
convenience and speed of developing with a disk drive, but I had no problem
returning to my native cassette environment when the project was completed.
The disk environment was much more convenient when working with multiple
projects or pieces of code/data. Within a year I had managed to convert a
couple of SA400s to Apple-compatible drives, and secured a clone Disk ][
Controller card, and I was in the DOS game. ;-)
I've never been tempted by nostalgia to return to my cassette-based
existence, but I'm proof that there was no intrinsic reliability issue with
Apple cassettes, and it was one of the fastest cassette interfaces around.
It was quite practical.
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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Re: What did an original Apple II sell for? [message #352449 is a reply to message #352438] |
Thu, 14 September 2017 17:12 |
Michael J. Mahon
Messages: 1767 Registered: October 2012
Karma: 0
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Senior Member |
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Michael J. Mahon <mjmahon@aol.com> wrote:
> Jorge <jorge@jorgechamorro.com> wrote:
>> A floppy rotates @300 rpm, a track has 16 sectors, a sector 256 bytes, a
>> byte 8 bits => a bit is read roughly every 1/(300/60)/16/256/8 -> 6µs
>>
>> On the tape a one takes 1000µs and a zero 500µs, so loading a bit takes 750µs on average.
>>
>> 600 dollars (1978 dollars!) bought you a 125x boost in speed, and that
>> alone was a good thing.
>
> Consider, though, the actual effect on "user speed".
>
> When I was developing Applesoft code (not unusual for 1980 ;-), I would
> rewind the cassette deck to the start of the last-SAVEd version and LOAD
> it. This would typically take a minute or less.
>
> Then I would edit and test the program for a session lasting an hour or
> two, then I would SAVE the new version after the old one--another minute.
>
> If, during the session, I made a big change (a new fork), I might SAVE one
> or two times within a sesssion.
>
> In any case, the few minutes spent LOADing and SAVEing was a minuscule part
> of my time at the computer.
>
> My first exposure to a disk-based Apple was actually just a two-month
> rental, to developed a piece of software. I certainly enjoyed the
> convenience and speed of developing with a disk drive, but I had no problem
> returning to my native cassette environment when the project was completed.
>
>
> The disk environment was much more convenient when working with multiple
> projects or pieces of code/data. Within a year I had managed to convert a
> couple of SA400s to Apple-compatible drives, and secured a clone Disk ][
> Controller card, and I was in the DOS game. ;-)
>
> I've never been tempted by nostalgia to return to my cassette-based
> existence, but I'm proof that there was no intrinsic reliability issue with
> Apple cassettes, and it was one of the fastest cassette interfaces around.
> It was quite practical.
>
BTW, last year I was poking around in the past and found my old cassettes.
I'm happy to report that they are as readable as ever, even though they
have outlasted the Panasonic deck that wrote them (so I had to create a
mapping from the original deck's tape counter to the new deck's counter)
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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Re: What did an original Apple II sell for? [message #352450 is a reply to message #352449] |
Thu, 14 September 2017 17:18 |
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Originally posted by: Jorge
On Thursday, September 14, 2017 at 11:13:02 PM UTC+2, Michael J. Mahon wrote:
>
> BTW, last year I was poking around in the past and found my old cassettes.
> I'm happy to report that they are as readable as ever, even though they
> have outlasted the Panasonic deck that wrote them (so I had to create a
> mapping from the original deck's tape counter to the new deck's counter)
The silly rubber belts! That happened to mine too...
BTW, Antoine, I have some cassettes that I believe are NOT in your collection yet :-)
--
Jorge.
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Re: What did an original Apple II sell for? [message #352466 is a reply to message #352389] |
Fri, 15 September 2017 01:33 |
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Originally posted by: Daniel Bethe
I'm glad to see another cassette player dropout, and amen to the holy gospel of the floppy drive. My first computer in third grade was an Atari 800xl and it came with a cassette drive and two tapes. My mom and I never ever got a tape to work. We tried and just didn't get it! We quickly traded that in for a 5.25" drive ;)
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Re: What did an original Apple II sell for? [message #352477 is a reply to message #352459] |
Fri, 15 September 2017 07:39 |
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Originally posted by: Jorge
On Friday, September 15, 2017 at 3:59:17 AM UTC+2, Antoine Vignau wrote:
> Jorge,
> please tell me which cassettes you have. If you cannot digitize them, I can.
https://imgur.com/a/Pzfck
Some come with manuals/booklets. Applesoft with the blue manual. I know there's twelve more but I could not find them at this moment.
If there's any one you don't have, which I doubt (*), I'll take pictures and digitize the audio and booklet.
(*) WOW, the cassette collection you've got @ brutaldeluxe is huge !!! Fantastic! But some of them without the audio, why?
BTW what's disk-o-tape? That sounds very interesting!
--
Jorge.
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Re: What did an original Apple II sell for? [message #352492 is a reply to message #352474] |
Fri, 15 September 2017 13:21 |
Michael AppleWin Debu
Messages: 1262 Registered: March 2013
Karma: 0
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On Friday, September 15, 2017 at 1:40:51 AM UTC-7, Jorge wrote:
> Sorry guys but just as 1200 baud is 872.7 bps, the disk II bps is 6µs/bit not 4 :-)
Your numbers are STILL off.
_How_ the nibbles are encoded effect the answer. Let's actually do the math.
First, recall that:
* The physical hardware takes 4 µs (microseconds) to read a bit.
* To read a full "disk nibble" -- which I'll hijack the normal "nibble" convention -- takes 4us * 8 bits / disk nibble = 32 µs/nibble.
# 4&4 Encoding
With 4&4 encoding it takes 512 nibbles to encode 256 bytes. That is, it takes a minimum of 32 µs + 32µs = 64 µs to read a full byte.
The total time to read 256 bytes/sector is:
= 512 nibbles/sector * 32 µs/nibble
= 16,384 µs / sector.
This gives us an _average_ time per bit of:
= 16,384 µs/sector / (256 bytes/sector * 8 bits/byte)
= 16,384 / 2,048
= 8 µs/bit.
# 6&2 Encoding
With 6&2 encoding it takes 342 disk nibbles to encode 256 bytes.
The total time to read 256bytes/sector is:
= 342 nibbles/sector * 32 µs/nibble
= 10,944 µs/sector
This gives us an _average_ time per bit of:
= 10,944 µs/sector / (256 bytes/sector * 8bits/byte)
= 10,944 / 2,048
= 5.34375 µs/bit
Now I didn't account for the Address field, nor Data Field -- namely the prologue and epilogue.
Address Field = D5 AA 96 v0 v1 t0 t1 s0 s1 c0 c1 DE AA EB + 8 sync nibbles
Where v# = volume, t# = track, s# = sector
= 14 nibbles * 32 µs/nibble + 8 * 40 µs/nibble
= 448 µs + 320 µs
= 768 µs
Data Field = D5 AA 96 [...342...] c0 DE AA EB
= 3 + 342 + 4
= 384 nibbles
Total time to read a sector:
= 768 µs + 384 nibbles * 32 µs/nibble
= 768 + 11,1,36
= 13,056 µs
This gives us an average time per bit of:
= 13,056 µs/sector / (256 bytes/sector * 8bits/byte)
= 6.375 µs/bit
Note: Both DOS 3.x and ProDOS waste space by doing dumb shit like using two nibbles for Volume, Track, and Sector EACH when only two nibbles are required for both the Track and Sector.
# 18 Sector
If instead we have "big sectors" such as Roland's RWTS18 which has 6 sectors of 768 bytes/track. This is equivalent to 18*256 = 4,608 bytes/track -- hence the name 18.
Total time to read a sector:
= 1,024 nibbles * 32 µs/nibble
= 32,768 µs
Average time per
= 32,768 µs / (768 bytes * 8 bits/byte)
= 5.33 µs/bit
# 19 Sector
Jon Brooks has mentioned you can use more then 64 "disk nibbles" -- all the way up to 81 nibbles reliably.
See:
* https://groups.google.com/forum/#!topic/comp.sys.apple2/6oyx BR4LpgA
> Total is 6211 nib = 49,688 trk bits
Minimum time to read a sector:
= 6,211 nibbles * * 32 µs/nibble
= 198,752 µs
This gives us an _average_ time per bit of:
= 198,752 µs / (19 sectors*256 bytes/sector * 8 bits/byte)
= 198,7752 / 38,912
= 5.107 ... µs
Where are you getting 6µs/bit again ??
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Re: What did an original Apple II sell for? [message #352498 is a reply to message #352492] |
Fri, 15 September 2017 14:14 |
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Originally posted by: James Davis
On Friday, September 15, 2017 at 10:21:54 AM UTC-7, Michael 'AppleWin Debugger Dev' wrote:
> * The physical hardware takes 4 µs (microseconds) to read a bit.
> * To read a full "disk nibble" -- which I'll hijack the normal "nibble" convention -- takes 4us * 8 bits / disk nibble = 32 µs/nibble.
I don't get that!? Isn't a nibble 4 bits? 4*4=16, right?
Stopped reading at your first math mistake.
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Re: What did an original Apple II sell for? [message #352499 is a reply to message #352405] |
Fri, 15 September 2017 14:23 |
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Originally posted by: James Davis
On Thursday, September 14, 2017 at 6:56:44 AM UTC-7, Jorge wrote:
> A problem of the cassette output of the Apple II is R19 (12k), all the Apple IIs I have had have that R shorted with a wire with test clips to make it compatible with the audio line input of the Macs. Works wonderfully! BTW this is also something the ADTPro user guide should mention because a Mac can't sense properly the Apple II microphone-level signal and that totally ruins ADTPro audio transfers for Mac users.
There is no R19 in the schematic for the enhanced IIe in my TRM. Are you talking about R18 or R6, maybe?
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Re: What did an original Apple II sell for? [message #352517 is a reply to message #352499] |
Fri, 15 September 2017 17:52 |
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Originally posted by: Jorge
On Friday, September 15, 2017 at 8:23:30 PM UTC+2, James Davis wrote:
> On Thursday, September 14, 2017 at 6:56:44 AM UTC-7, Jorge wrote:
>
>> A problem of the cassette output of the Apple II is R19 (12k), all the Apple IIs I have had have that R shorted with a wire with test clips to make it compatible with the audio line input of the Macs. Works wonderfully! BTW this is also something the ADTPro user guide should mention because a Mac can't sense properly the Apple II microphone-level signal and that totally ruins ADTPro audio transfers for Mac users.
>
> There is no R19 in the schematic for the enhanced IIe in my TRM. Are you talking about R18 or R6, maybe?
Is this the schematic?
http://www.applelogic.org/files/IIESCHEMATIC.pdf
If so, it would be R6... BUT I would not short it in the IIe because it's not coming off a cheap LS TTL but from a CMOS ASIC. Better safe than sorry: I'd put a 200 or 300Ω resistor in parallel with R6 NOT a short.
--
Jorge.
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Re: What did an original Apple II sell for? [message #352523 is a reply to message #352498] |
Fri, 15 September 2017 21:47 |
Michael AppleWin Debu
Messages: 1262 Registered: March 2013
Karma: 0
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Senior Member |
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On Friday, September 15, 2017 at 11:16:28 AM UTC-7, James Davis wrote:
>> * To read a full "disk nibble" -- which I'll hijack the normal "nibble" convention -- takes 4us * 8 bits / disk nibble = 32 µs/nibble.
> I don't get that!? Isn't a nibble 4 bits? 4*4=16, right?
Yes, normally, nibble means 4 bits but we are talking about _disk nibbles_ here as I pointed out. The hardware could initially only read alternating bits reliably so the restriction was that every other bit was set to 1. So even though you were reading/write a byte it wasn't the _full_ byte -- only a full valid nibble of data. The name is unfortunate but regrettable.
Over the years Woz relaxed the rules for the disc controller to allow two consecutive zeroes.
> Stopped reading at your first math mistake.
/Oblg. Chronicles of Riddick: "You made three mistakes."
Your first mistake was _assuming_ I coined a new term.
Your second mistake was being ignorant of history.
You DO realize that _Woz_ himself, the inventor of the Disk II controller, called them nibbles back in 1979, right?
COREQUS.S
https://htmlpreview.github.io/?https://github.com/Michaelang el007/apple2_dos33/blob/master/dos33.html#COREQUS
017 ***************************
018 * *
019 * MAR 18, 1979 *
020 * WOZ *
021 * *
022 ***************************
053 * NIBLIZING TABLE 'NIBL' *
054 * (64 BYTES) MAPS 6-BIT *
055 * NIBLS INTO VALID 7-BIT *
056 * NIBLS. THIS TABLE *
057 * MUST NOT CROSS A PAGE *
058 * BOUNDARY. *
Also, why did Roland Gustafsson the creator of RWTS18 call them "disk nibbles"?
https://youtu.be/ScFrXoD99hw?t=33
; Valid disk nibbles
;
NIBBLES HEX 96979A9B9D9E9FA6
HEX A7ABACADAEAFB2B3
HEX B4B5B6B7B9BABBBC
HEX BDBEBFCBCDCECFD3
HEX D6D7D9DADBDCDDDE
HEX DFE5E6E7E9EAEBEC
HEX EDEEEFF2F3F4F5F6
HEX F7F9FAFBFCFDFEFF
Your third mistake was pretending to know more then you think you do.
Next time spend more time reading "Beneath Apple DOS" before flaming someone and pretending to understand a topic such as the Disk Controller.
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Re: What did an original Apple II sell for? [message #352537 is a reply to message #352517] |
Sat, 16 September 2017 02:14 |
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Originally posted by: James Davis
On Friday, September 15, 2017 at 2:52:51 PM UTC-7, Jorge wrote:
> On Friday, September 15, 2017 at 8:23:30 PM UTC+2, James Davis wrote:
>> On Thursday, September 14, 2017 at 6:56:44 AM UTC-7, Jorge wrote:
>>
>>> A problem of the cassette output of the Apple II is R19 (12k), all the Apple IIs I have had have that R shorted with a wire with test clips to make it compatible with the audio line input of the Macs. Works wonderfully! BTW this is also something the ADTPro user guide should mention because a Mac can't sense properly the Apple II microphone-level signal and that totally ruins ADTPro audio transfers for Mac users.
>>
>> There is no R19 in the schematic for the enhanced IIe in my TRM. Are you talking about R18 or R6, maybe?
>
> Is this the schematic?
>
> http://www.applelogic.org/files/IIESCHEMATIC.pdf
>
> If so, it would be R6... BUT I would not short it in the IIe because it's not coming off a cheap LS TTL but from a CMOS ASIC. Better safe than sorry: I'd put a 200 or 300Ω resistor in parallel with R6 NOT a short.
>
> --
> Jorge.
Yes, Jorge, if not the same, very similar. I thought it might be R6. Later, it occurred to me to check the Apple II/II+ TRM schematics, and I found R19 there. It does correspond to R6. Good to know not to short it out completely. I think M.J.M. has written about this in the past also.
James Davis
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