Cassette Baud increase

[Wally1]

there is a vector to increase the cassette baud rate,

 

can somebody post the details?

 

thanks

Wally

 

[Rybags]

No such thing exists.

 

For reading the OS uses a timing algorithm to know what to set Pokey to, there's tables in the OS to cover a given range. The objective there being to cater for motor speed variance, tape stretch etc.

 

For writing, a number of possibilities without resorting to the hardware mods to the tape drive itself (the tape drive actually converts the tones back to serial 0/1 values):

 

- create your own Ram-based SIO routine.

- copy the OS to Ram, overwrite the values that get stored to the AUDF registers to increase the bitrate.

- flash or burn EPROM OS with such mod in place.

 

- preferred, I used this one: VBlank Immediate routine which sets the AUDF registers to the desired rate when doing the write to tape.

I used this in conjunction with a 2-stage booter with very large blocksize on the second part to practically halve the load time for an 8K copy of the Atari AsmEd cartridge.

 

Problem with using custom blocksize is the OS doesn't cater for it in any way, so you'd either need a Ram-based C: handler replacement if dealing e.g. with BASIC programs or a 2-stage booter as earlier described.

2-stage booter generally useful only if the program to be loaded occupies a contiguous block of Ram or at least can be loaded that way and later relocate.

 

Data compression is another thing - a program that can be loaded then quickly inflated in place is a good candidate. Speed of re-inflate of course important, not much use other than saving media space if the thing takes minutes to decompress.

[Wally1]

thanks for your thoughtful response

 

but I found this:

 

60294 EB86 .... To increase the cassette baud rate by almost one-third and reduce the time of the leader from 20 to 10 seconds, POKE the following:
POKE Address Value Hex

60294 00 $EB84, $00 low Byte, Write baud

60299 04 $EB8B, $04 high Byte 61250 00 $EF42, $00 low Byte, baud rate init routine

61255 04 $EF47, $04 high Byte 61346 00 $EFA2, $00 baud rate Open routine

61351 04 $EFA7, $04 high Byte 61371 02 $EFBB, $02 leader time

 

don't know what to make of this

 

[Rybags]

They're addresses in the OS Rom. But they don't match up with the OS I have set in Atari800Win+ - mine's several bytes out.

 

That'd be copying OS to Ram and patching as I earlier described. The leader shortening I never bothered, you can accomplish the same using Pause on the tape drive.

 

Too much bitrate increase it becomes very unreliable. I experimented a bit years ago, unsure what I came up with but it wasn't a massive increase. But using larger blocksize contributes greatly although that too can decrease reliability a little.

[Wally1]

so is it basically a matter of a few simple pokes?

[Kyle22]

I haven't played with cassettes in years, but, in addition to increasing the baud rate, would it be necessary to speed up the drive motor to increase tape speed?

[sup8pdct]

There was an upgrade for cassette used in eastern europe. But it required some hardware added to the csssette drive it self and i think a cable to a joystick port?. It could only be used on the xc cassette players only i think?

 

James

[ricortes]

A little more info on what Rybags is saying because I think it may be being missed. The pokes given will only work if you have used a utility to copy the os ROM to the RAM underneath. This means you can't do it on an 800/400 or with Sparta DOS.

 

The baud rates are hard coded in ROM so the defaults would get loaded everytime you called the routines. Only alternative is to bypass those routines by writing your own handler.

[Rybags]

Altering motor speed isn't necessary. In any case you'd need to slow it down for saves and speed up for loading.

 

The electronics by default I believe will only work if a certain minimum number of pulses at each frequency used are present, which presents one of the limitations to speeding up tape operations.

 

In the modern day, the disk emulation stuff is so much better and barely more expensive than modding a tape drive, so made it somewhat redundant.

[TXG/MNX]

Hi,

 

There were several mods for the cassette

 

- Turbo 2000, it did have a cartridge aswell with the loader and utils

- Turbo 6000 a mod in magazine

 

Several other home made mods.

 

Not a real speed mod, but in the old days there was in the Netherlands something called BASICODE this was a universal basic for C64, atari and more. The programs written for it where send thru the air by the FM radio station. Everyone with a modded cassette could record at home there program and load it. I had an Atari 1010 modded with this mod but it's useless now, there are no broadcasts anymore...

 

Sometimes I miss those beeps and long loading times, especially when I bought a new game and was wondering how it would be when it was loaded. Sometimes several boot attemps where needed or I did forget to disable basic while loading... I even remember games that would load over 20 minutes...

[+wood_jl]

I had always wished for this, back in my early-80s Atari 410 days.

 

Commodore got "TurboTape" from Compute! Magazine:

 

https://archive.org/stream/1985-01-compute-magazine/Compute_Issue_056_1985_Jan#page/n125/mode/2up

 

(turn the pages by mouse click)

 

.....something for Atari tape users to be jealous over.

[Wally1]

the Netherlands is a cool place

[thorfdbg]

there is a vector to increase the cassette baud rate,

 

No. And there are other problems, too. The reading routine of the Os allows some "lee way" in the interpretation of the baud rate it receives, but it also has some limits. The major problem is, however, not actually the ROM, but the hardware. While encoding of the FM based casette data is done within POKEY, decoding happens in the actual tape teck, and the frequencies of the filters are there set in stone by the hardware. It's not microprocessor-based, its really an (or rather two) analog filter. The filter response times also set limits to the baud rate, so that's not easily changed.

 

Os++ (the operating system that comes with Atari++) will include in its next release an improved tape handler that improves the baud rate a little bit, mostly by writing 256-byte blocks instead of 128-byte blocks and by using a slightly higher rate that is still within the limits of the frequency decode table. But don't expect miracles. Too much depends on the actual hardware to allow much variation.

[w1k]

TURBO Q or
TURBO DNM - 2000-10 000 BAUD

 

i using UNIVERSAL TURBO, 6000b no problem..

 

software:

http://atari.turiecfoto.sk/soft/

 

search - TURBO D, Q, QNM, etc

 

Edited November 23, 2013 by w1k