PDP11/84 continued

From: Doc Shipley <doc_at_mdrconsult.com>
Date: Sun Sep 28 22:07:58 2003

Tony Duell wrote:
>> Well, with only the RX211 installed in its original slot, the M9302
>>terminator properly installed, and G7273's everywhere else, the CPU
>>still hangs. With G727A cards instead of G7273's, the RX02 will boot an
>>RT-11 installation floppy.
>
> You are telling me it will work with the single-height grant cards in
> slot D, but not with the dual-height ones in C and D?

   Yes. Specifically, with G272A grant cards in slot D of rows 5-10 and
row 12,
  an RX211 in C-F of row 11, and an M9302 terminator in AB of row 12, the
11/84 will boot from an RT-11 floppy in an RX02 drive. Replace the G727A
cards with G7273 dual-height cards, or add other boards, and the boot
aborts
with a Controller error.

> This is impossible -- the only difference between the 2 types of grant
> card is that the dual-height ones also complete the NPG jumper. If it
> works with the single-height ones, then the NPG chain must be complete
> along the backplane. Adding a second 'jumper' (on the dual height card)
> in parallel with the wire-wrapped on on the backplane can't make any
> difference.

   That's actually good to hear. It doesn't make sense to me either.
I've pulled
the backplane (H9277-A), and there are no broken traces or any other obvious
damage, but there are no jumpers between the first pins of slot C in
*any* row.
There is a lot of wire-wrap back there, but I'll be a couple of days
just mapping
it, much less figuring out the purpose.

> It sounds like you have backplane problems. Maybe some of the dual-height
> cards aren't making proper contact. Maybe the slots you're putting them
> in aren't satnadard Unibus slots (unlikely, but...) and the 'extra'
> jumper is shorting a couple of signals that it shouldn't...

   This machine was in production till about 2 months ago, and was
reportedly in
good health when decomissioned. However, it's not acting in a manner
that I'd
expect from anything I've read.

   At this point, I'm looking at the 11/44 next to it an thinking that's
gotta be better.
   :)

   As bad as it sounds, the primary goal is to validate a couple dozen
RA60 disk
packs, not nw\ecessarily to bring up the 11/84. Whatever gets us there
quickest is best.


        Doc
Received on Sun Sep 28 2003 - 22:07:58 BST