DEC PDP-14 Programmable Controller simulator

Charles Dickman chd at
Tue Apr 4 19:57:09 CDT 2017

On Tue, Apr 4, 2017 at 8:35 PM, Paul Koning <paulkoning at> wrote:
>> On Apr 4, 2017, at 8:21 PM, Charles Dickman via cctalk <cctalk at> wrote:
>> ...
>> In the course of research, I saw that there was an option to replace
>> the braided core ROM that was standard,  ...
> Charles,
> I've been studying core ROM for a while now, and there doesn't seem to be a whole lot of information.  One interesting tidbit is that it appears -- but it's hard to confirm completely -- that it was invented by Ken Olsen (while at MIT Lincoln Labs).
> Do you have pointers to the PDP-14 rope memory documentation?

Forgive me if I have used "braided core ROM" incorrectly, but how I
understand the PDP-14 ROM, it was a network of wires threaded
(braided) through ferrite pulse transformer cores in a way such that
it was possible to address and read data. The current sources and
sense amplifiers were similar to that used with core memory.

>From what I can gather, never having seen one, the cores in the PDP-14
were actually quite large and fragile. There is information in the
field service handbook (Bitsavers) that indicates that a ROM could be
destroyed when the board was pulled from the chassis and there was a
manufacturer change made to prevent the problem.


More information about the cctalk mailing list