Which Was Better: Punch Cards, Paper Tape, or Audio Tapes?

[krebizfan]

https://archive.org/details/dec-edu-price-list-january-1973/page/12/mode/2up shows a set of prices for 1973 which is about when audio cassette storage started appearing.
The simple punch/reader added about $350 to the price of the ASR-33. The PC11 high speed paper tape punch was $3,900 while the CR11 slow card reader was $4,000 with the high speed CD11 at $10,000. A CPU driven audio cassette might need several dollars in components plus a cassette deck which would be less than $50. One can put up with a lot in order to keep the money needed for a second car.

Since this is the S100 topic, the Tarbell Cassette Interface was $195 but is much more complicated than the home computer designs. The Tarbell floppy controller was only $100 more.

 

[cjs]

One can put up with a lot in order to keep the money needed for a second car.

Well, not to mention that my first thought about that CDC card reader was that I'd need to hire a crane, because it won't fit through the door of my apartment.

Since this is the S100 topic, the Tarbell Cassette Interface was $195 but is much more complicated than the home computer designs.

ISTR that one (and a few of the other really early ones I looked at) used a UART, rather than just bit-banging it. Quite a lot of extra hardware! And it's not like doing bit-banged tape I/O is all that bad. Recently I disassembled the save and load routines on the TK-85 trainer board, which used not much more than a couple of GPIO pins for the interface, and it wasn't terribly complex.

 

[Robbbert]

That cassette interface (the CMT) is quite a simple one where all the work is done in software. I've seen some early Kansas-City ones where they used upwards of 30 ICs, and as you can imagine it wasn't terribly reliable.

 

[pbirkel@gmail.com]

I don't see why "30 ICs" implies unreliability. With that IC count you can implement both an XTAL controlled oscillator and use a real USART for encode/decode. I suspect, though, that you're talking about a pre-USART implementation. FSK itself shouldn't be an issue; long used in the RTTY world with good results once one factors out issues specifically related to (multi)path distortion. That seems to leave the inherent problem of wow/flutter in the tape transport alongside tape drop-out due to poor coating. In both cases there's a limited amount of compensation that a controller can implement.

 

[Pentad4k]

Thank you all for the information! It has been interesting to read! In the book, Fire in the Valley, they mention that MS Basic was widely pirated and had a copy of Bill Gates' Pirate Letter. May I ask a few more questions:

1. The book said MS Basic was on paper tape, so was paper tape easy to copy? Could you copy from paper tape to paper tape or did you have to load the program into the computer and then save to a new paper tape?

2. Was saving to paper tape much slower than loading from paper tape?

3. With regards to punch cards, could you copy from punch cards to punch cards or did you have to load the program into the computer and then save to new punch cards?


Thanks!

 

[Chuck(G)]

My 8800 came with MS BASIC on both cassette and paper tape. Loaned the cassette version to a friend with an IMSAI and he clobbered the data.

 

[g4ugm]

Thank you all for the information! It has been interesting to read! In the book, Fire in the Valley, they mention that MS Basic was widely pirated and had a copy of Bill Gates' Pirate Letter. May I ask a few more questions:

1. The book said MS Basic was on paper tape, so was paper tape easy to copy? Could you copy from paper tape to paper tape or did you have to load the program into the computer and then save to a new paper tape?

If you had an ASR33 Teletype you could copy from tape to paper tape without even having a computer. However both paper tape and audio cassette tape are both just byte streams. Typically the computer can't tell the difference. So you can easily convert between the two.

2. Was saving to paper tape much slower than loading from paper tape?

If you had an ASR33 the speed was the same. However as I said many people build their own optical tape readers which were much faster. All you need is nine photo leds , 8-data and one for the clock track, plus a few Schmitt triggers, and a parallel input port. Because the clock is generated from the feed holes you can simply pull the tape through, or use a simple roller feed.

Other terminals might have had different rates. Take look at this UK Club newsletter from 1978, page 8 and see some used terminals with readers and punches. So in many cases saving or copying was slower.

3. With regards to punch cards, could you copy from punch cards to punch cards or did you have to load the program into the computer and then save to new punch cards?

If you had a punch, yes you could copy. Usually card punching was slower than card reading. Also as each card is a fixed length then it may not be so easy to copy between cards and tape as tape has variable length records.

Thanks!

no probs.

 

[krebizfan]

Thank you all for the information! It has been interesting to read! In the book, Fire in the Valley, they mention that MS Basic was widely pirated and had a copy of Bill Gates' Pirate Letter. May I ask a few more questions:

1. The book said MS Basic was on paper tape, so was paper tape easy to copy? Could you copy from paper tape to paper tape or did you have to load the program into the computer and then save to a new paper tape?

2. Was saving to paper tape much slower than loading from paper tape?

3. With regards to punch cards, could you copy from punch cards to punch cards or did you have to load the program into the computer and then save to new punch cards?


Thanks!

1) Very easy to copy. There were some automated paper tape copying systems but I think most did the load into computer and print it out on the local punch because the punch duplicators were uncommon.

2) Low end paper tape like those with the ASR-33 teletypes were the same speed for both writing and reading. High speed paper tape generally would read a lot faster than it could punch. Check a few manuals if you are curious about the specifics.

3) Punch card duplicators existed from before computers and I think were more common than computer driven card punches. https://www.glennsmuseum.com/items/ibm_514/ shows one.

 

[Chuck(G)]

Punch card duplicators existed from before computers and I think were more common than computer driven card punches. https://www.glennsmuseum.com/items/ibm_514/ shows one.

cf. "Unit Record Equipment" https://en.wikipedia.org/wiki/Unit_record_equipment
Simple, robust and efficient. I know of at least one outfit that acquired a 360/20 to replace its UR gear. Took additional personnel to run and was more expensive--and less reliable. Said outfit terminated their computer lease and put the UR stuff back.
A number of early IBM computer models (e.g. 1401) were introduced with the goal of displacing the UR equipment being used in many firms.

 

[cjs]

1. The book said MS Basic was on paper tape, so was paper tape easy to copy? Could you copy from paper tape to paper tape or did you have to load the program into the computer and then save to a new paper tape?

MS-BASIC was on paper tape in part because it was before CMT interfaces became common, and in part because it was created (and much of the testing done) on a mainframe, which had no CMT facilities anyway.

If you had an ASR33 Teletype you could copy from tape to paper tape without even having a computer. However both paper tape and audio cassette tape are both just byte streams. Typically the computer can't tell the difference. So you can easily convert between the two.

This isn't quite true. Every CMT format I've seen has at least a little bit of metadata, if only for a header containing a file number. Most are blocked formats, with checksums and the like as well. So the straight byte-stream coming off a tape (usually seen in .CMT files) will contain more than just the file data.

 

[g4ugm]

This isn't quite true. Every CMT format I've seen has at least a little bit of metadata, if only for a header containing a file number. Most are blocked formats, with checksums and the like as well. So the straight byte-stream coming off a tape (usually seen in .CMT files) will contain more than just the file data.

Perhaps on systems with dedicated tape like the , but for example on SWTPC systems we just used the same format. So the same S9 format data went to both paper tape or cassette.

 

[Hugo Holden]

I was impressed with the tape recording and data recovery system in the SOL-20, I wrote a detailed article about it and added timing diagrams:

www.worldphaco.com/uploads/The_SOL-20_tape.pdf

In PT’s 1200 Baud system, the tone decoder circuitry, processing the data from a played back tape, has to be able to identify the 600 Hz tone from only one half cycle of it in the audio stream, compared to the Kansas City format where there are a minimum of 4 cycles of tone to process or identify. It turns out that PT’s clever tone decoder only requires ½ a cycle of the 600Hz tone to identify it quickly. I think the tone decoder is very clever.

Use of XOR gates to make frequency doublers and transition detectors, as well as a recover clock PLL system ad an excellent amplitude leveling system on the tape replay signal. All of that helped minimize errors from drift in the cassette players. PT's system was a much more elaborate system than found in other computers like the AIM65. In the same way PT sold the VDM-1 video card, that basically was the SOL's video system on an s-100 card, they did the same thing with their Tape system on their CUTS card.