Atari 8-bit turbo loaders?

[analmux]

Look here....maybe this is interesting (about frequencies used on tapedrive)

 

http://64.233.183.104/search?q=cache:L53pb...+xl++tape&hl=nl

 

http://www.atariarchives.org/dere/chaptC.php

Edited October 26, 2005 by analmux

[ijor]

The main limitation may be the minimal time before the tapedrive detects a one or a zero from a certain tone on the tape.

 

No. The whole point of using advanced encoding is that you can increase the effective bit rate without increasing the transition rate. If we could use RLL 2,7, for example, we'll get 900 bps using the same period between tone changes.

 

I'm still not sure we could do it. RLL decoding is quite complex and very slow because it involves lot of bit shifting. But might be, don't know.

 

But as I said before, even without using RLL. We could use a simpler 1 to 1 encoding, like MFM that we can decode without doubts. And because it is self clocking you remove the start and stop bits. Then you get a real bit-rate of 600 bps, while the current one is 480 (600*8/10).

 

i think Fox' Fastpacker is one of the fastest packers ...

 

But here we don't need the fastest packer. We need the packer that compresses the most, and yet decompression is not awfully slow at the A8.

 

Load time is so slow in comparison to decompression time, that you can afford much slower decompression if you gain a bit in compression size. Compression time is not an issue at all.

[Wrathchild]

Hi,

 

Don't get too worried about the compression side -

you're not going to be doing 'on-the-fly' decompression

from the input stream. Decompression would be left until

all the data has been loaded into memory as per most

of the compacted binaries of games you can download.

 

Personally I'm not to keen on these as the user has patient

followed something like a 'blocks to load' counter, but after

this goes to zero you still have to wait another period of

time (say 30s to 1min) waiting for the data to decompress.

If it is tucked into loading a level then that's not so bad

(but loading levels from tape is not too friendly - Ace of Aces)

 

Regards,

Mark

[Wrathchild]

Look here....maybe this is interesting (about frequencies used on tapedrive)

 

http://64.233.183.104/search?q=cache:L53pb...+xl++tape&hl=nl

 

http://www.atariarchives.org/dere/chaptC.php

954893[/snapback]

Hi,

 

I was looking at that last night - the sync mark does seem to be the

thing to use, so scanning $D20F 5th bit (e.g. AND #$10) should work.

 

Now to find that IM loader code...

 

Regards,

Mark

[ijor]

I was looking at that last night - the sync mark does seem to be the

thing to use,

 

You don't need any sync mark. Sync marks are used on digital recording (and in other cases as well) for several reasons, none of them apply here.

 

You just load the custom loader in the first stage, a small gap, then start the custom decoded loading.

[Wrathchild]

Hi,

 

I was thinking more in terms of using the principles of the mastering

process shown in De-Re, but yes it should be possible to either

a) write a save routine to run include in your program so that you can,

for example, boot from floppy/SIO2PC to memory and then call

the save routine to write the data to cassette in 'Turbo' blocks

b) Have a PC application that takes a file and load address and it

then generate the WAV file for you.

 

Also, I'd guess that the may not be CAS format compatible?

 

Mark

[ijor]

I was thinking more in terms of using the principles of the mastering process shown in De-Re,

 

Oh. But De-Re mastering using the term "sync mark" is about recording real audio on the audio channel. But this is not what we are talking about here. Or is it?

 

Also, I'd guess that the may not be CAS format compatible?

 

I recall reading that CAS2WAV has some limited support for custom tape formats. But don't know if this is supported by actual CAS applications (emulators, SIO2PC, APE).

[ijor]

... so that you can, for example, boot from floppy/SIO2PC to memory and then call the save routine to write the data to cassette in 'Turbo' blocks

 

One more thing I forgot. If you are going to use a custom encoding, then you won't be able to write from the Atari. You can bypass Pokey when reading, but not when writing. For best quality you don't want to master using an Atari tape anyway.

 

I mean WAV2CAS, and NOT CAS2WAV in the previous post :oops:

[Rybags]

It might even be worth using a C-64 to generate such a cassette.

 

I'm fairly sure that their tape drive records in mono, which would eliminate any interference from the audio track on an Atari recorder.

 

In any case, an interesting concept/idea, but about 20 years too late.

[+CharlieChaplin]

Well,

in my opinion the DJ packer(s) and Code Cruncher(s) are the best packers up to date. But afaik, Numen and other demos used even better packers (ZIP or similar routines)...

 

If you wanna use turbo tape loaders via software only, I know of three programs that can do this:

 

1) File Copier 3.x - copies a diskfile to tape (and vice versa); has a 37kbytes buffer; can use standard 600 baud or "faster" 800 baud; The tape can be loaded in the normal way then, e.g. with a standard tape loader for *.COM / *.EXE / *.XEX files (non-boot-tapes), like BLC or COS or other tape file loaders;

 

2) Speed Tape by german magazine Computer Kontakt; this is a basic program that converts a diskfile into tape format (don`t know if it still uses file-format or if it produces a boot-tape); the manual says it saves with approx. 1000 baud but leaves the gaps unchanged; since it uses Basic, I guess the buffer is <32kbytes (minus the program)...

 

3) CBAUD: another type in program by german Atari Magazin; uses a Basic program to convert a normal tape from 600 baud into 1200 baud format and a *.COM / *.CAS file to load in the 1200 baud turbo tape; afaik the maximum program length (for loader and converter) is somewhere in the 30-37kbytes range ...

 

(Or another tape copy/tape converter program that was mentioned here...)

 

So, let`s imagine you still wanna save some A8 game onto tape today and load it with a software based turbo, you can a) pack the game with a good packer (and append the depacker to it) and also b) save it with 800, 1000 or even 1200 baud and load it with a normal or special loader. there is no hardware upgrade for the tape drive required then... But as always: We western Atarians prefer disk-based software !!! -Andreas Magenheimer.

[+CharlieChaplin]

Well,

afaik BW tape was only? used to convert BW-DOS (yes, DOS - Disk Operating System) onto tape and load it from there with some added / changed functions...

 

another tape copier / tape converter mentioned here might be the Happy Turtle Copy... (I never used it, but it might be useful too)... -Andreas Magenheimer

 

P.S.: PPS - can you send me a copy of this Happy Turtle Copy, please ?!?