C64 Tape Port

[trekiej]

Fast do you think the C64 Cassette Port runs?
1\8 * 1 or 2 MHZ = 128k or 256 k.

Was there ever a fast cassette for the C64?

[RobertB]

Fast do you think the C64 Cassette Port runs?

A C64 runs at 1 MHz.  The cassette port transfers at 50 bytes per second.

Was there ever a fast cassette for the C64?

If you are talking about fast loaders/savers for cassettes on the C64, yes.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug

[spirantho]

To be precise, the cassette port samples at 1000000 (more or less)  ticks per second, allowing a theoretical throughput of (1000000/8) bytes/s = 125KB/s.

That's a completely theoretical limit, of course - no loader gets even close (the ROM loader being 50 bytes/s) but in theory if you could sample reliably that to work out if the flux had changed or not you could get that rate. If you wrote a routine to check for changes in flux that often and connected it to a digital input, you could get that rate if your tape routine consisted of one instruction - which of course it won't.

In reality, I believe the fastest loaders were probably running at about 300 B/s (2400 baud) but that's just a guess from what I've observed.

[polyp2000]

If my maths is right - doesnt that mean it should be possible to record an 8bit 22khz sample via the tape port - with some headroom?

[trekiej]

If my maths is right - doesnt that mean it should be possible to record an 8bit 22khz sample via the tape port - with some headroom?

That is kind of what I am thinking.

[psxphill]

In reality, I believe the fastest loaders were probably running at about 300 B/s (2400 baud) but that's just a guess from what I've observed.

You run into problems with frequency response before you run out of CPU speed. There were fast loaders that had to be slowed down because the duplicators couldn't cope with them.
 
You have to take into account what the tape is made of & the analogue to digital conversion in the C2N.
 
Writing a 1 bit audio sample to the tape at full speed would be kinda interesting. However I don't think the bit that you write gets put straight onto the tape, I believe there is some additional circuit in the C2N. IIRC the zero's and one's are modulated on the tape somehow, not just stored as is.

[jlariv8957]

Back in that days I remember having tried  a program published on a book that samples audio tapes played by the tape port, the sound was not that good but it was funny and was running so it was possible..

[polyp2000]

I've often wondered if sampling could also be achieved via the joystick port (isnt there an A2D converter for the pots in the paddles ? )

might not be too high resolution though.
N

[Darrin]

The cassette port transfers at 50 bytes per second.

That fast?!  It seemed slower.  

[spirantho]

If my maths is right - doesnt that mean it should be possible to record an 8bit 22khz sample via the tape port - with some headroom?

Not a chance, I'm afraid. The tape port is digital, not analogue, and is serial. You can write a '1' to it, and you can write a '0' to it, but that's all.

When you read the tape on a C64, the downward transition triggers an interrupt via the VIA (if you see what I mean). You don't have full control of the wave, just transitions from +ve to -ve.

Sorry.

@PSXPhill
That's basically what I was trying to get across, yes.

[LoadWB]

That fast?!  It seemed slower.  

You're confusing that with the 1541 drives...

[LoadWB]

Not a chance, I'm afraid. The tape port is digital, not analogue, and is serial. You can write a '1' to it, and you can write a '0' to it, but that's all.

When you read the tape on a C64, the downward transition triggers an interrupt via the VIA (if you see what I mean). You don't have full control of the wave, just transitions from +ve to -ve.

Sorry.

@PSXPhill
That's basically what I was trying to get across, yes.

Not necessarily.  COMPUTE! Magazine had an ML program for the Apple which read the cassette in port in single-bit precision.  As well, we played with a similar program on the TI-99/4A which did essentially the same thing.

It was scratchy and sounded pretty horrible, but it did work.  In fact, one year I went away for school I sent an Apple floppy made in one of my classes to my old class and computer instructor on which I recorded me dictating my letter to them.

[RobertB]

...doesnt that mean it should be possible to record an 8bit 22khz sample via the tape port...

Oh, if you needed an audio digitizer, then those would go through the C64 user port.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug

[trekiej]

How about a tape port to tape port transfer? Has this been done?
The cart port I guess would go at a speed of 8/8 * 1 mhz = 1 MB/sec. theoretical.
I did see a video of the introduction to "Dallas" played from a REU.

[trekiej]

Has anyone here used a 64hdd ( http://www.64hdd.com )before?
If so, how did you like it?