DEC MM15 core mem found

Jay Jaeger cube1 at
Tue Dec 8 08:01:11 CST 2015

But not these - PDP-11's didn't use dual-height connectors on memory.

Anyway, they are indeed PDP-15.  (Whether or not they are actually MM15
I don't know).  The page on the memory on the provided link indicates:


The modules and options document on sez....

G100  Sense Amp & Inhibity Driver, PDP15, 3 Wire, 3D Memory
Where Used: 15

G613  X Diode Matrix, 3 Wire, 4K, 9/I  Where Used: 15
G614 X Diode Matrix, 3 Wire, 4K, 9/I Where Used: 15


On 12/8/2015 6:14 AM, Johnny Billquist wrote:
> Careful. Some PDP-11 memory is also 18 bits wide... 16 bits plus two
> parity bits.
>     Johnny
> On 2015-12-08 13:03, Pontus Pihlgren wrote:
>> I've seen a memory assembly from a PDP-15 and it looks very much like
>> this. Also, if each connector pair corresponds to one bit it adds up to
>> 18 which matches the word lenght of a PDP-15.
>> Of course, PDP-1, -4 and -7 used 18 bit word lenght, but they were not
>> made with flip-chips.
>> PDP-9 is made with flipchips and is 18 bit. But I seeem to recall it's
>> memory looks quite different.
>> /P
>> On Tue, Dec 08, 2015 at 11:58:07AM +0100, Jörg Hoppe wrote:
>>> I help cleaning out a large repository of DEC parts.
>>> There a quantity of DEC core module assemblies appeared.
>>> According to PDF docs these must be PDP-15 MM15's, but no labels are
>>> on the
>>> boards.
>>> I show/offer some of them at
>>> ,
>>> under "core memory"
>>> Can somebody confirm they are MM15's?
>>> Are any PDP-15 running at all?
>>> Thanks,
>>> Joerg

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