[Coco] tape format

[Joel Ewy]

Roger Taylor wrote:
> At 09:02 PM 11/17/2008, you wrote:
>> Hi Roger,
>>
>> For some reason, I thought the Coco did have 1500 Hz cassette system.  I
>> seem to remember it being exactly 5 times faster than the Commodore.
>>
>> In any event, what was the speed of the Coco cassette?
>>
>> John
>
> They claim an average of "1500 baud" because of the random assortment
> of 1200 hz and 2400 hz sine waves.
>
> The 2400 hz wave is only output once on a CoCo.  Some old vintie
> systems output 2 of the 2400 hz waves so the duration is the same as
> the 1200 hz wave.  To me this would probably give better reliability
> with cheap tapes depending on the formula, averaging, and testing used
> in the load-back code.  The problem has always been the drag on the
> tape causing the record and play rates to both vary slightly over
> time, like if you held your finger on one of the rotors ever so
> slightly similar to slowing down an LP record platform.  This is why
> data stored in blocks loads back more reliably.  The loader gets a
> chance to get back in sync more often.
> I just think that with our modern way of thinking and time-tested
> experiments over the ages, that a much faster and reliable tape audio
> format could be created that would blow the lid off the old format,
> even using cheapo tapes.  I *might* save all that for a rainy day
> after cocotape.exe is done, but I doubt it.
>
> Btw, cocotape will have a ~1mhz and ~2mhz save option so you can type
> POKE 65495/7,0 on the CoCo and load twice as fast from the PC since
> it's a perfectly steady audio stream with no tape drag or drop
> factor.  The default will be the ~1mhz speed, ofcourse.
>
So, could you come up with a client/server system where you CLOADM a
small routine at 1MHz from the host PC which auto-executes, patches
BASIC's cassette routine (assuming CoCo 3 or RAM-able 64K CoCo) for the
faster protocol, and optionally switches the computer to 2MHz?  Then
subsequent loads would zip.

JCE