Date   : Sun, 03 Aug 2003 03:59:48 +0100
From   : Jon Ripley <beeb@...>
Subject: Re: Acceptable bounds of baud rate

In message <Pine.LNX.4.53.0308012008020.21787@...> you wrote:

> On Fri, 1 Aug 2003, Jon Ripley wrote:
> 
> > In documentation the Electron is 1200 baud only and the BBC is 300/1200
> > baud. Not sure about what the actual limits are but the implemtation
> > surely must allow for tape players playing at slightly different speeds,
> 
> As on the beeb the 6850 handles the tape, then it's documented tolerances
> are what the tape tolerances are - so RS232/423 type tolerances.
> 
> I would expect the Electron ULA to have similar tolerances.

The tolerances for the Electron would most likely change depending on
the current screen mode. The Elk was reported to be unreliable when
saving to tape in at least screen modes 0-2.

I have been doing some searching on the web but haven't found much. The
Wikkipedia has some info but not much.

One possible (naff?) idea could be to simulate loading a file from a
slightly dodgy fast/slow tape player. 

1. Create a file a few blocks long, 1k is about four tape blocks.
2. Use your local firendly PC as a tape recorder and save the file,
   sample it at as high a rate as possible.
3. Reload it to make sure it worked.
4. Play the sample back at a different rate, maybe 1% faster/slower each
   time.
5. Try and load the file.
6. Repeat steps 4 and 5 until file will not load anymore.

A seperate test would be needed to see if 1195 and 1205 (etc) baud files
would load from a tape player running at the correct speed as it seems
that resampling the save to a different baud rate may destroy the data.

Waffles,
Jon R.
-- 
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