> On Mar 13, 2021, at 1:34 PM, Joshua Rice via cctalk <cctalk@classiccmp.org> 
> wrote:
> 
> 
>> Very interesting looking.  I can't quite make out what is going on in that 
>> rectangular area where all the wires terminate, labeled 0-15 and A-R.  Are 
>> there diodes there?  Anything on the other side of that board?
> 
> Nothing but traces on the other side, though you’re right on them being 
> diodes.
> 
>> The large cores with all the wires are remisniscent of core rope ROM.   If 
>> so, I wonder if it's AGC (Lincoln Labs) style, EL-X1 style, or a scheme 
>> different from either of those two.
> 
> It’s definitely some form of core rope ROM. 
> 
> Interestingly, the ferrite rings are built in pairs, with a "selection" coil 
> wrapped around both, joining them. Therefore (i assume, i’m really no expert) 
> they’ll be a positive pulse induced when passing through one coil, but a 
> negative pulse when passed through the opposite coil. This probably helps in 
> differentiating beween a 0, a 1, or a NULL state (ie 0v). 
> 
> I have no idea if that correlates with any particular format of Core Rope, 
> but as far as my eyes can tell, that’  how the core rope is woven and 
> functions.

The key component of core rope memory (and X1 ROM) is square-loop cores, like 
the cores used in conventional read/write core memory.

There is another kind of core ROM where the cores are simply transformer cores. 
 Since you mentioned a "selection" coil, chances are that's what we're dealing 
with here.

Brent Hilpert has a great writeup on a number of the technologies used.  
http://madrona.ca/e/corerope/index.html 

        paul

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