Core Blimey

I'm in the process of finishing some 2-to-4 decoder modules for the first stack address decoder, and building up a second one. But I'm also starting to think about the core matrices themselves as it will soon be time to work on them.

One of the questions to answer is: a 3-wire or 4-wire system? A 4-wire system (X, Y, Sense, Inhibit) is easier but of course means threading 4 wires through each core. In a 3-wire system, the sense and inhibit circuitry share the same wire. This complicates the electronics a bit, and also requires that the sense/inhibit line be threaded in a way that reduces noise immunity during sensing.

So I did a quick test on a piece of veroboard to see how easy it would be to get 4 wires through a core. It turns out that it's not too bad:

This image is taken through a 30x microscope (which I use when I'm hand-soldering SMDs). The central hole that the core is sitting in is 2mm in diameter. The wires are 0.16mm in diameter. The horizontal wire is X, the 2 vertical wires are Y and inhibit, and the diagonal wire is the sense wire.

So, a 4-wire system it is.

Discussions

Andrew Starr wrote 12/09/2015 at 08:47

It's a fairly substantial roll, and very thin wire, so I don't think I'll be running out. There will be 512 cores per stack (8 x 8 x 8). Sounds like a lot, but I have soldered literally over a thousand SOT-23 transistors to get this far, not to mention the SOD-523 BAT54 Schottkys and 0603 resistors and capacitors. Threading a few wires doesn't daunt me at all :)

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Yann Guidon / YGDES wrote 12/09/2015 at 12:30

They all say that for sn#01 ;-)

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Andrew Starr wrote 12/08/2015 at 17:58

The same place everyone else does - a Bulgarian dude on Ebay. Came in a cool Soviet-era cardboard box for a radiation counter!

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Yann Guidon / YGDES wrote 12/08/2015 at 19:15

I looked and... wow...

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Yann Guidon / YGDES wrote 12/08/2015 at 19:15

Do you use thin enameled wire from relays or similar coils ?

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Andrew Starr wrote 12/09/2015 at 08:17

I'm using a roll of ancient wire that I found when cleaning out my office (I'm an electronics engineer). It's probably meant for winding filters and rf transformers. When I found it I immediately thought it would be perfect for my memory cores, so I 'liberated' it :)

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Yann Guidon / YGDES wrote 12/09/2015 at 08:25

How long is the wire ? You're going to use a LOT of it...
Good luck with passing so many wires in so many tiny holes :-/

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Yann Guidon / YGDES wrote 12/08/2015 at 14:59

Where did you find your ferrite cores ? :-)

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Stack Address Counter: Some Numbers

Data and Return Stack address decoders

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