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Re: Core memory

>Timothy van der Linden writes:
> > > > Why doesn't the magnetic field in the ferrite core degrade? (I
assume the
> > > > ferrite has some resistance.)
> > >
> > >Have you ever known other magnets to degrade?  Once magnetized, a
> > >material won't demagnetize unless exposed to heat above its Curie point
> > >or another sufficiently strong magnetic field.
> > 
> > Oh, now I understand, you create a permanent magnetic field just like
> > magnetic discs and tapes. (I though you created a current in the core) So in
> > fact the cores don't need to be closed completely.
> > 
> > Tim
>The core is in essence just a lump of magnetizable material; they were
>generally made toroidal because it was easiest to string them that way.

Hmmm, I would think that an open loop would be easier. After cross-wiring
the grid, you could simply "clip" the "cores" over the cross-sections. This
in contrast to the weaving. Anyway, its clear.

>There were some designs for magnetic memory that didn't use cores, but
>(if I recall correctly) used spots of magnetic material sandwiched
>between two layers of parallel conductors.  And even more exotic memory
>hardware has existed -- ever heard of mecury delay lines?  Williams

Nope, never heard of.

Thank you for explaining.