CPC Tape Loading System

[chinnyhill10]

Anyone know if the CPC uses the Kansas City encoding system as the default tape loader or did Amstrad write something custom? In terms of 'sound', it's unlike what the BBC uses (which does) but sounds close to what the Spectrum uses.


Anyone have any idea? Thanks.,

[Docent]

Anyone know if the CPC uses the Kansas City encoding system as the default tape loader or did Amstrad write something custom? In terms of 'sound', it's unlike what the BBC uses (which does) but sounds close to what the Spectrum uses.


Anyone have any idea? Thanks.,

No, its a completely different system - Amstrad's bit 1 is half the frequency of bit 0, while Kansas encoded bit 1 is double the frequency of 0. Amstrad's bit 1 takes twice the time of 0, on Kansas both 1 and 0  take the same time. Also bits are stored in different order - on Amstrad most significant first, on Kansas least significant first.
There are also other differences like speed, cycle size (1 for Amstrad, 4 or 8 for Kansas) etc.

[mr_lou]

Semi-related geeky useless question coming up:

Would it be possible for the Amstrad CPC to copy a tape from/for another system? I.e. just load the data, and write it back.

E.g. "C64 copy" for the Amstrad CPC. 

[Bryce]

Semi-related geeky useless question coming up:

Would it be possible for the Amstrad CPC to copy a tape from/for another system? I.e. just load the data, and write it back.

E.g. "C64 copy" for the Amstrad CPC. 

Why bother with the CPC at all then? Just connect two tape decks together.

But to answer your question: Probably not. The amplifier circuitry that converts the frequencies to bits is tuned for the CPC frequencies, if the other system used different frequencies they wouldn't be recognised as bits.

Bryce.

[chinnyhill10]

No, its a completely different system - Amstrad's bit 1 is half the frequency of bit 0, while Kansas encoded bit 1 is double the frequency of 0. Amstrad's bit 1 takes twice the time of 0, on Kansas both 1 and 0  take the same time. Also bits are stored in different order - on Amstrad most significant first, on Kansas least significant first.
There are also other differences like speed, cycle size (1 for Amstrad, 4 or 8 for Kansas) etc.

Fantastic. Thanks.

[Cholo]

Semi-related geeky useless question coming up:

Would it be possible for the Amstrad CPC to copy a tape from/for another system? I.e. just load the data, and write it back.

E.g. "C64 copy" for the Amstrad CPC. 

Actually "Spectrum Read" for the Amstrad CPC already excits. Program was publish all the way back in 86' (ACU no 20, juli 86) along with full assembler source code & compiled code &  a bunch of schematics of the normal spectrum loading scheme (no protected). Even includes a "spectrum screen resized to amstrad" pogram, so you can load up spectrum loading screen and view them on your 464.


I had a bit of fun with it here (even works with emulators):

https://www.youtube.com/watch?v=k4Qi3nyBCEk


However the real question is .. can the 464 tape mechanism write back in a format that a spectrum will recognise. The 464 is obviously quite "open minded" however how picky is the spectrum when it comes to reading data? If i recall right they jumped thru some hoops by "lifting" code from the spectrum firmware (hehe Clive probably dont read Amstrad magazines so there is little chance we will get sued) & guessed on some timings as well. Perhaps these timings arnt correct & would make the spectrum error out.


A completely different approach that i dreamt up in my teens was to copy games digitally. Like i had great fun playing around with Digitizer program (JLCS), aka putting a empty tape into my stereo cassette system, then using a mic id record a short message onto the tape. Then put the tape into the 464 & digitize it into memory, then save it back as data for use in my own basic programs.


Of cause the bitrate was low & the message short & limited to the 64kb ram. But today i have 1mb on my symbiface 2 so recording a fairly simple (and "unprotected") data audio signal should be possible & perhaps writing it back as well? Again im no audio/cassette wizard in any way & it probably completely depend on the system. Like a similar z80 system like the zx81 probably could work but who knows what goes on with the C64 & other systems, especially if they have all kinda weird mastering protections to prevent copying. Also can the 464 tape deck even handle audio out properly (aka as well as it can handle audio in).

[GUNHED]

Would it be possible for the Amstrad CPC to copy a tape from/for another system? I.e. just load the data, and write it back.

Of course, in case another system would work with 0 and 1 only. But it would take up enormous amounts of memory, because you read-in a kind of wave consisting out of 0 and 1. And the more often you read, the better the quality will be at the end.
As Bryce mentioned: Use a well tape deck