Plessy core memory

Chris Zach cz at
Sun Jan 9 16:04:20 CST 2022

I'm working on my pdp11/10 getting it back together. One problem I think 
I have is that the secondary memory (a Plessy 700101-100) may be 
shorting the -15 line for some reason. Working on it, but does anyone 
have a manual or anything like that for this kind of memory board?

Alternately, what kind of Unibus 16k memory board exists to get a 11/10 
from 16kw to 32kw of memory? Apparently I can't use a MM11-B as it 
requires +20 and -5, both of which are not provided by the power supply 
or sourced on a DD11-B backplane module. The 11/10 has +15, -15, and +5.

On a related note, where did +20 come from for Unibus and which systems 
even supported it? Was it an 11/45,11/70 thing?


(Yes, I could build a regulator to take the 30 volts between +15 and -15 
and create an independent 20 volts. Maybe. Likewise I could generate -5 
from the -15 and a 7815 regulator. Maybe.)

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