PDP-8/L troubleshooting (was Re: New acquisition, and question)

From: Ethan Dicks <erd_6502_at_yahoo.com>
Date: Sun Oct 13 09:08:00 2002

--- Loboyko Steve <sloboyko_at_yahoo.com> wrote:
> On the FOCAL issue, I think I read that FOCAL can't
> load text very quickly - you have to stop and start
> the tape every line or two.

An ASR-33 for DEC hardware has a "reader run" relay and
current loop. The CPU steps the reader one character at
a time to prevent this sort of thing. My ASR-33 _is_
one of these.

> I have noticed this with
> my PDP/8e clone and not-very-fast (around 100 CPS)
> paper tape reader. It may use its own intepreter to
> store coding in RAM, so it might be very slow in this
> area.

The DEC highspeed reader controls the tape feed, just like
a TTY. This sort of thing was a problem in the old days, so
DEC engineered solutions for it.

> If you can load FOCAL itself in via paper tape,
> this kind of proves that the PTR itself is OK.

The PTR itself is OK. Where I suspect the problem is in the CPU.
The BIN loader (which loads FOCAL) does not use a wide range of
instructions. I expect that I have a dirty card edge or blown gate
that is causing less-common instructions to fail in interesting
ways. I need to sit down with the diag tapes (which I have) and
the instructions (which I also have) and run this box through its
paces, one paper tape at a time.

> --- Ethan Dicks <erd_6502_at_yahoo.com> wrote:
> > Got some minor processor glitch I haven't tracked
> > down yet... I get the FOCAL prompt, but it won't load
> > Hammurabi...



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Received on Sun Oct 13 2002 - 09:08:00 BST

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