13 Sep
2015
13 Sep
'15
12:02 p.m.
On 09/13/2015 02:52 AM, Henk Gooijen wrote:
-----Oorspronkelijk bericht----- From: Charles
Sent: Sunday, September 13, 2015 12:36 AM
To: cctalk digest
Subject: Re: Even more PDP-8/A weirdness (was: Re: PDP-8
diagnostics SR settings?)
As previously posted, reseating the boot ROMs in their
sockets cured the
corrupted boot loader issue. Got lucky there :)
As before, the AJRLHA diagnostic (Seek/Fctn) still faults
and prints errors,
but only at the start of testing the drive. Thereafter
that drive shows no
errors. Then the program will switch to the other drive
and the same problem
occurs. Specifically (edited and reformatted for clarity,
with results
interpreted from the RL02 user manual):
[... snip ...]
Any help making sense of this mishmash of errors would be
greatly
appreciated :)
I'm pretty far away from competence on PDP-8s anymore, but
the symptoms sound like maybe the drive faults on LONG
seeks, but as long as the seeks are short, it works OK.
There might be a one-shot in the controller that allows so
many ms for a seek to complete, and due to aging capacitors,
the delay is now too short. But, that's a totally wild
guess, there could be troubles in the drive seek electronics
that only occur on longer seeks.
Jon