Riging together a way to store data on an audio cassette

[reds4ever]

Originally posted by Sir Ralph


Vertical blank interrupt, once every 20 milliseconds. There was also a horizontal blank interrupt at the end of every screen line, which could be used to switch graphics modi and screen colors, quite effectful.

Vertical blank interrupt, thats the one

The horizonal was used to get extra colours on the screen buy 'kidding' the pooter and get the colours for two graphics modes, different world isn't it?

[Urban Ranger]

Originally posted by Sir Ralph
The problem with the storage is, that you have to create vibrations (to make the sound for storage). Obviously, if stored directly, the bit sequence 000000... would produce silence on the tape. But if you have a sequence of 111111..., it would also translate into silence, because there are no oscillating bits.

Are you sure of that? Because you should be getting a flat tone, like striking a what-you-might-call-it fork thing.

[Urban Ranger]

Originally posted by reds4ever
Anywho the 6502 was sh!it the Z80(a) was the mutts nutts

Yup. 6809 rocks

[Harovan]

Originally posted by Urban Ranger
Are you sure of that? Because you should be getting a flat tone, like striking a what-you-might-call-it fork thing.

Very sure. You can't get a flat tone like striking a "what-you-might-call-it fork thing" without providing an analogous sinusoidal vibration. Remember, we are talking about ordinary cassette recorders. They aren't able to store digital signals, like on TTL level, only analogous vibrations.

[reds4ever]

This thread has got me thinking (no mean feat!), is there a decent 'History of personal computing' type book out there?

I've read one on Apple (whose title eludes me) that was a very interesting.

[The Mad Monk]

Yep!

This is where is was getting my information earlier.

[The Mad Monk]

http://www.old-computers.com/museum/computer.asp?st=1&c=18

The computer I learned BASIC on. We had five of them in my high school's computer room.

[reds4ever]

Nice site Monk, I'll be whiling away a few hours on it in work tomorrow

[Urban Ranger]

Originally posted by The Mad Monk
The computer I learned BASIC on. We had five of them in my high school's computer room.

That's a Model III isn't it? Nice box back then.

[The Mad Monk]

Yep! Two of them even had floppy drives!

The other three relied on Tandy "datacorders", or whatever they called them...

[Harovan]

This is the computer I learned BASIC on (to be fair I'd have to add, that I already knew FORTRAN from my studies).



The difference is, that the model on the picture has 3 floppy drives 5.25", while the machine I worked on had one 8" floppy drive and 2 more 8" drives on an additional device. It had an U880 processor (Z80 clone made in GDR) at 2.5 MHz, 64 KB RAM, the operating system was SCP (a CP/M clone) and it had a 64x16 greenish monochrome text-only monitor.