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

[Bill Degnan]

Agreed.  I was able to get the TTY current loop secure, which is a good
first step.  I have a reader relay I can install.  I have some no name ones
too.  But it's going to be a while, RAM is an issue first.  Dave Gesswein
pointed out a few things I should check/do next.  I can load simple
programs but bits they are a droppin.

On Sat, Jul 8, 2023, 3:27 PM Ethan Dicks via vcf-midatlantic <
vcf-midatlantic at lists.vcfed.org> wrote:

> 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
>