Re: Cassette port / CD-Rs

[mjmahon@aol.com (Michael J. Mahon)]

In article <226198.SRHJCMKA@news.telusplanet.net>, Simon Williams
<*email*@*luddite.ca*> writes:

>As a matter of fact, I was just playing around with using my Mac as 
>'tape' storage for my Apple IIe. I've never actually used tape, so I
>can't make a comparison, but I was able to save/load a few small
>programs with little difficulty. I recorded the output at 16/44100,
>which is probably a bit OTT. Since the bit-stream is 1-bit, 300 baud
>(if I'm not mistaken), it should be okay to record at a much lower
>quality -- I think 8-bit/800 Hz is probably the lowest any modern 
>software will do, but even that is likely more than adequate.
>I had thought about converting the audio to MP3 and seeing if it
>still worked, but I got side-tracked.

Actually, it's about 1500bps, with 0's recording as one 2000Hz
cycle and 1's recording as one 1000Hz cycle (or is it the other way
around? ;-).

Since the information is in the times of the zero crossings, I think
you'd want a sample rate at least five times the max frequency, or
greater than 10kHz.  Of course, only one bit of resolution is needed,
since the signal is a squarewave.

>As far as emulators go, I'm sure it would be possible to write a
>program that could create a .WAV file from a specific range of memory.
>That way you could use a decent audio player to load the program
>into your Apple II, thus avoiding any problems with the emulator's
>sound output.
>
>I think 'perfect loads everytime' might be a bit much to shoot for
>since the biggest problem is likely to be getting a clean signal from
>one machine to another -- it's been my experience that computer mic
>and headphone jacks are not usually the most rugged of components.

The real issue is of practicality.  Cassette I/O, at 1500bps, is about
187 bytes/sec, and that is _slow_ by any standard.  Add to this the
fact that cassette files are either Applesoft Basic files or binary files,
both saved without any name or type info, and you can see that the
cassette drive is not the most capable file system.  ;-)

Recorded cassette signals are good for nostalgia, but little else.
A null-modem cable is cheap, ten times the speed, and is supported
by protocols that preserve file names and types.

-michael

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