PDP-11/34A rebuild project Was: Re: Post-move diary

From: Christian Fandt <cfandt_at_netsync.net>
Date: Wed Mar 31 21:25:09 1999

Upon the date 05:03 PM 3/31/99 -0500, Megan said something like:
>>They go from the 10 pin connectors on the frontpanel control board
>>(KY11B) to either the spare 10 pin connectors on the FPU next to the top
>>connector or to the 2 10 pin blocks of the connector on the CPU
>>(control?) board that the FPU top connector goes onto (this will make
>>sense if you're looking at the machine). Again I can't remember the
>>twists, but try it until maintenance mode works, I guess.
>I figured that's what they did... but I didn't want to simply plug them
>in without knowing which way was correct, and which way *might* let some
>magic smoke escape...
>I found the 10-pin ribbon cables in some sort of paddle board which is
>marked as an FP11-A extender board... it has male and female connectors
>of the type used to connect the CPU and FPU, but at opposite ends of the
>board. It *also* has two sets of fingers, one of which is *obviously*
>wire as a grant card... what the heck is this thing, and how is it used?

Wow! Cool! Looks like you have a W9042 Extender Board which is specifically
described as part of the FP11-A Option in my KK11-A tech manual and by
association, one is also part of the KK11-A cache option. The manual
mentions: "The W9042 Extender board Assy. is stored in the backplane and
used for some maintenance operations."

When you have to use an extender board to troubleshoot the adjacent M8265
in a cache-option-only system, the W9042 plugs into the top connector on
the M8268 Cache module and then the over-the-top connector plugs the two
together. If troubleshooting the M8268, then the W9042 is plugged into the
top conn of the 8265 and the o-t-t conn board connects both together. Neat!

Same for troubleshooting the systems with both cache and FP11 options
except two W9042s are used.

As for storing it in the backplane, DEC apparently chose to make some use
of the thing by using it as a G727A type device. No details at all
mentioned in my KK11-A cache tech manual about the W9042, just a simple
line drawing showing how it and the M-boards are used together. Maybe
something further is said about the extender in the FP11-A tech manual but
I have none.

Since you say it has two sets of fingers with one wired as BG, and the line
dwg I see sure looks like it has two fingers, then it likely is stored in
slots C-D. This assumes the DEC service person has a G727A or two in his
tool box as when the W9042 is used, there would be no BG otherwise.

>BTW - I found an extra set of KD11-EA processor boards... so I
>tested them in my machine today and they worked fine. I'm glad to know
>that I have some spares for the machine...

I've got an extra set of them too plus a cache. No spare FP11 tho. Notice
how heavy that FP11 is? Sure is a lot of 'stone' in all those AMD 2901s!

Regards, Chris
-- --
Christian Fandt, Electronic/Electrical Historian
Jamestown, NY USA cfandt_at_netsync.net
Member of Antique Wireless Association
        URL: http://www.ggw.org/awa
Received on Wed Mar 31 1999 - 21:25:09 BST

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