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Re: Obit - Sir Clive Sinclair, Computing Pioneer [message #411184 is a reply to message #411179] Thu, 23 September 2021 18:21 Go to previous messageGo to previous message
Anonymous
Karma:
Originally posted by: Carlos E. R.

On 23/09/2021 21.55, Peter Flass wrote:
> Charlie Gibbs <cgibbs@kltpzyxm.invalid> wrote:
>> On 2021-09-23, Rich <rich@example.invalid> wrote:
>>
>>> In comp.os.linux.misc Peter Flass <peter_flass@yahoo.com> wrote:
>>>
>>>> Carlos E. R. <robin_listas@es.invalid> wrote:
>>>>
>>>> > On 22/09/2021 21.57, Andreas Kohlbach wrote:
>>>> >
>>>> >> On Wed, 22 Sep 2021 09:13:12 +0200, Carlos E. R. wrote:
>>>> >>
>>>> >>> Might not work (a capture). Just a guess. If you do try,
>>>> >>> make sure to not use mp3. Now that I think, I would try the
>>>> >>> experiment, to find out.
>>>> >>
>>>> >> There was a short lived [1] UK computer show "4 Computer Buffs"
>>>> >> <https://www.imdb.com/title/tt1178499/> I never heard of before.
>>>> >> They sent program data via audio the audience record. When I found
>>>> >> the show on Youtube I tested that (extracted the audio at that
>>>> >> position) and ran the resulting WAV in an emulator fir that
>>>> >> particular machine on my PC. It my amazement it worked.
>>>> >
>>>> > Wow.
>>>>
>>>> Systems that saved programs on cassette used an audio format. Due to
>>>> the sloppiness of the media, I think the recording format had to be
>>>> pretty robust.
>>>
>>> At least in the case of the Atari 400/800 cassette format it was a very
>>> simple format:
>>>
>>> Format details are here: https://www.atariarchives.org/dere/chaptC.php
>>>
>>> 132 byte records, two start bytes for 'speed detection', a control
>>> byte, 128 data bytes, and a single checksum byte (and the checksum is
>>> just a simple endaround carry sum of the 131 other bytes in the record).
>>>
>>> The physical byte encoding on the tape was frequency shift keying, with
>>> 5327 Hz for a mark and 3995 Hz for a space.
>>>
>>> So it at least it had a simple checksum, but the packet format was
>>> hardly "robust". Workable, but memory of those days was that the
>>> cassette was quite flakey as a data storage format, sometimes it
>>> worked, sometimes it did not. And when it did not rereading things all
>>> over again sometimes magically had them work.
>>
>> Ah yes, I remember the good old days with my IMSAI. I didn't have
>> cassette decks, but I had a couple of reel-to-reel decks, so I broke
>> into their motor circuits and built a control box that would use the
>> cassette motor control circuits to activate relays to switch 110-volt
>> motor power on and off.
>
> I was astonished when I got my first home computer with a cassette drive
> that it didn’t do this!

I have a foggy memory that it used the switch on/off wires of the
microphone, which in some/all tape machines stopped the motor.

That would be the Sinclair Spectrum if any, but can't vouch for it.


--
Cheers,
Carlos E.R.
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