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Core memory
- To: T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)
- Subject: Core memory
- From: Steve VanDevender <stevev@efn.org>
- Date: Mon, 11 Mar 1996 14:21:44 -0800
- Cc: KellySt@aol.com, kgstar@most.magec.com, stevev@efn.org, jim@bogie2.bio.purdue.edu, zkulpa@zmit1.ippt.gov.pl, hous0042@maroon.tc.umn.edu, rddesign@wolfenet.com, David@InterWorld.com, lparker@destin.gulfnet.com, bmansur@oc.edu
- In-Reply-To: <199603111531.AA26695@student.utwente.nl>
- References: <199603111531.AA26695@student.utwente.nl>
Timothy van der Linden writes:
> To Steve,
>
> Thanks for explaining the core-memory so clearly (Your ascii-art looks great)
>
> >Although it takes more current to read or write a core than it takes to
> >update a semiconductor memory cell, no power is required to maintain the
> >state of core memory. It wasn't until about the mid-70s that
> >semiconductor memory became all of faster, denser, less power-intensive,
> >and cheaper than equivalent amounts of core memory, and core was still
> >used for some time after that.
>
> 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.
Magnetic materials have a certain amount of resistance to being
magnetized. An external magnetic field won't affect the material until
it exceeds a certain strength; then the material is magnetized to the
orientation of the externally-applied field. This is why only the core
at the intersection of the two address wires is magnetized; the current
sent through the address wires creates a magnetic field around the wires
lower than this threshold, but the sum of the fields at the intersection
of the wires is greater than this threshold.
> Timothy
- References:
- Core memory
- From: T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)