[vcf-midatlantic] Pdp-8 focal @ Kennett Classic

[Ethan Dicks]

On Fri, Jul 7, 2023 at 10:39 AM Duane Craps via vcf-midatlantic
<vcf-midatlantic at lists.vcfed.org> wrote:
> Just set the sender to 1.5 or 2 stop bits. That will cover for minor
> speed differences. TTYs sent 1.5 stop bits for that reason.

Model 15 and friends (5-level "Baudot") used 1.5 stop bits.  ASR33 used 2.

Definitely need the stop bits because the mechanical devices have
required recycle times to get rotating things back around to the top.

But there's also pacing problems between chars.  The reason the DEC
LT33 adds the Reader Run Relay to the standard ASR33 is because if the
TTY is sending chars back to back but the PDP-8 is off processing
previous chars, it's going to fail to keep up and you'll lose chars.
It happens with the RIM and BIN loaders but it's especially pronounced
when reading programs into interpreted languages like FOCAL and BASIC.

At the last couple of VCFs, I had to put huge, huge delays (many
milliseconds) at the end of each line when sending FOCAL and BASIC
programs to a real PDP-8/a running BASIC or FOCAL.  Also had small
delays between chars, but the EOL pauses when the interpreters went
off to process the entire line were extensive.

I wish you luck with reading in FOCAL on an ASR33 without a Reader Run
Relay.  It might be successful but I wouldn't be surprised if you just
can't.  You could probably have some luck reading in a tape image from
a modern machine that dribbles the chars into the PDP-8.

-ethan


-ethan


-ethan