The weird stuff I keep finding: 19 bit core memory?

Noel Chiappa jnc at
Fri Oct 23 10:48:31 CDT 2020

    > (Whether that's all done on the companion driver boards, and the H21x
    > card would just bring the wiring of the two banks out to the edge
    > connector in parallel, letting the driver board do what it wants, I
    > don't know - you'd have to look at the MM11-L engineering drawings/TM.)
    > The other possibility is that the PDP-10 memory used these boards in
    > pairs.

It's not either!

First, I looked at the MM11-L TM, and it talks about how the H214 has "mats"
(2D arrays of cores), 1 mat per bit; the H214 has 16 mats. So definitely no
effectively 36+ bit wide variant. So, pairs?

Well, I looked to see what PDP-10 memory TM's were extant, and there's one for
the MF10 (A-MN-MF10-0-MAN-1); and glancing in it, it _does_ use the H216 -
with "19 mats" to produce "19-bit word memory banks"! (Exactly how, I didn't
have time to stop and read. It's got to be pairs, but at the bank level, not

So our guess as to which generation of PDP-10 memories it was used in might
have been wrong...


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