[cctalk] Re: Core memory (was Re: Computer Museum uses GreaseWeazle to help exonerate Maryland Man)

[Will Cooke via cctalk]

> On 02/02/2023 10:03 AM CST Sellam Abraham via cctalk <cctalk@classiccmp.org> 
> wrote:
> 
> 
> This discussion on core memory got me thinking:
> 
> Is it possible to "read" core memory by examining each core using some kind
> of instrument that would sense its "charge" (or lack thereof)
> non-destructively?
> 
> Could a piece of paper be placed over a core plane and fine particles of
> iron sprinkled onto the paper to literally "see" the bits?
> 
> Please excuse me for any ignorant assumptions made here on my part.
> 
> Sellam

I suspect it would be possible, but not easy.  The main reason I say that is 
that the toroidal shape of the cores, rather than something like a square or 
straight bar, is intended to keep the magnetic field contained within the ring. 
 Instead of coming out an end or edge and going through free space, the 
magnetic lines of force go circularly around the loop.  The polarity of the 
field determines whether it is clockwise or counterclockwise.  So very little 
field escapes.  That's what makes it possible to have them packed so tightly 
without interference.
https://en.wikipedia.org/wiki/Toroidal_inductors_and_transformers

Will