Re: NEWSFLASH! Linux ported to Commodore VIC-20!!

Stephen Landamore (stephenl@arcam.co.uk)
Tue, 15 Sep 1998 11:15:55 +0100


John Berthels <John.Berthels@nexor.co.uk> wrote:
> [another poster mentions 32K being reasonable...]
>
> The ZX Spectrum routines ran at 1500 baud, but it was entirely
> possible to copy the routines to RAM from ROM and tweak the timing
> constants. 4500 baud was pretty reliable (although you had to be
> careful with tuning the 'tone' and volume on the tape) on a good
> quality tape.
>
> (60 mins @ 4500 bits/sec ~= 2Mbytes)
>
> Going higher than that would probably be a bit speculative (although
> if you have a decent sound system...).

The Spectrum ran at 1500 baud but in my experience 4500 baud was pretty
reliable - anything more tended to be a lose.

I think the limitation was the actual hardware interface on the
Spectrum, it stuck out PCM data (nice square waves don't record very
well :-) and had essentially a comparator as input (fixed level
reference and 1-bit ADC input :-)

With improved hardware (i.e. sound card) then I see no reason why the
data rate couldn't be increased to modem-like rates (10's of kbaud),
especially since audio cassettes have several times the bandwidth of
phone lines...

> Hmm....could you run CDs in audio mode and sample that? :-)

Around about 1988 a company released a CD with simple interface to
connect to a Spectrum... (it was the people who did the Dizzy range of
games, Codemasters I think, but my memory is foggy...) Since this was
towards the end of the Spectrum's life, and since all (20 or so) games
had been previously released on cassette, it's hardly surprising this
didn't take off. IIRC with Cd quality audio they were able to up the
data rate to about 6000 baud. I never owned this bit of hardware, never
saw it in the shops, and have never seen one since... if anyone has one
I'd be interested to hear about it :-)

regards,
stephen

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